May 052014
The Champion 3100W inverter/generator - currently our pick as best small inverter/generator for Level 1 type situations.

The Champion 3100W inverter/generator – currently our pick as best small inverter/generator for Level 1 type situations.

(You can see our definition of levels one, two and three type events here.  It is a useful categorization that provides structure to your problem analysis and preparation planning.)

When some people – particularly preppers – start thinking about generators, they immediately think of enormous noisy diesel standby generators, in special generator sheds, and capable of providing tens of kilowatts of power for extended periods, drawing off multi-hundred gallon storage tanks.  Don’t get us wrong.  We love diesel generators with a passion, and we also agree there’s no such thing as ‘too much’ power.

But these types of installations will typically cost $10,000 and up, will guzzle gas at a rate of several gallons an hour, are definitely impractical for apartment dwellers, and frankly are overkill for the times when you have a short power outage lasting anywhere from a few hours to a few days.  In these short time frames, we can compromise some of the convenience we normally enjoy with abundant and available power throughout our home, and also avoid needing to adjourn to our retreat to ride out the problem.

All we want is a small convenient and ‘low profile’ portable generator that we can run without drawing way too much attention to ourselves, and keep the essential parts of our home operating.

No matter if you have major industrial-grade generators or not, we suggest everyone should have one of these small generators – and here’s the key concept.  Get a small one.  Don’t ‘over-engineer’ the problem and end up buying something that generates enough power for you to have every appliance in your house all operating simultaneously.  For a short outage, all you need is lighting, some essential electronics, and some power to share between your fridge and freezer at times, maybe a stove top or other cooking facility at other times, and perhaps heating or cooling at still other times.

How Much Generating Power Do You Need?

We repeat.  Don’t over-engineer things.  And note the question.  We’re not asking how much power you want, or would like.  We’re asking how much you need, in order to sustain life and a moderate level of comfort and security, for a short duration of no more than a few days.

So, to sustain life, you need air, shelter, water and food, right?  Let’s think about each of those.

Air – hopefully you already have air!  And hopefully also you can get fresh air without needing to drive some sort of fan or other motorized appliance.  So presumably this does not need power.

Shelter – a bit more complicated.  We’re assuming that you’re in your regular residence and it is unharmed, so you have four walls and a roof already.  But also part of shelter is some amount of heating or cooling.  You know the seasonal weather extremes for where you live and you also know what you have installed in the form of hvac appliances.  But perhaps for a short-term solution, you should not aim to heat/cool your entire residence, but work out a heating/cooling plan for just a couple of rooms only.

Maybe you have a central hvac system, and in the winter you only need a small amount of power to drive the fan, with heat coming from natural gas.  That would be ideal, and natural gas seems to continue flowing, no matter what happens to the power.  But, even so, humor yourself next winter-time.  Do a ‘what if’ worst case scenario test and see how many 1500 W heaters you would need to keep a central living area warm without your hvac.  Hopefully you’ll be able to get by with only one.

As for summer, again perhaps you have a central air system, but for the purposes of this exercise, can you also have a window unit that controls temperatures in just one room?  A small generator is probably inadequate to handle the power needs of a central air system, but is probably suitable for a typical RV sized 13,500 – 15,000 BTU type unit.

One other part of shelter – some lighting.  Perhaps now is the time to start picking up LED lights when you see them on sale, so that you are getting maximum light for minimum watts.  Indeed, the LED lighting is so good (and so long-lived) that there’s no reason not to use them all the time, in all your lights.

So – heating, cooling, and lights.  That’s pretty much everything you need for short-term shelter requirements, right?  Maybe you have something else to also plan for, like a cellar sump pump?  Try not to overlook anything else that might be essential.

Water – do you have any water pumps (under your control, as opposed to operated by the building you live in)?  If not, then hopefully (maybe) you’ll continue to get water from your taps during a power outage, and if you don’t, that’s a matter for another article.  And what about waste water?  Some people have macerator units on their toilets, or pumps operating their septic system, but other than that, most of us have gravity powered waste water systems (at least out of our house, beyond that, in the city system, there might be other issues, which are again outside the purview of an article about low powered home generators!).

The only other consideration about water would be if you wanted warm/hot water.  If you have gas water heating, maybe you have an electronic pilot light (although these are not so common on hot water heaters) in which case you need power for the hot water to work.  Otherwise, if you have electric hot water heating, that will be a problem, because the elements in your water heater probably draw 5kW – 10kW of power, and that is more than you should reasonably expect from a small portable generator.

There are two workarounds for that.  The first is a small ‘under sink’ type water heater.  The other is to simply heat up or boil water on your stove top.  Worst case scenario, if you have to go without long hot baths/showers for a few days, that’s truly not the end of the world.

Food –  There are a couple of things to consider when it comes to food.  The first is food storage – ie, your fridge and freezer.  Ideally you want to keep these powered up, at least some of the time, so you don’t have all the food in your freezer spoil, and so you are able to maintain a cool temperature in your fridge too, besides which, depending on the nature of the power outage, you might need that food to live on.  Find out how much power your fridge (and freezer, if separate) use when they’re running; we’ll tell you what to do with those numbers in a minute or two.

The second part of food power needs is cooking your food.  There are several ways you can prepare food using relatively small amounts of power.  Your microwave is an efficient and effective way of preparing many food items.  A small toaster oven is another choice, and a stand-alone hotplate/element is a third choice.  You might also want an electric jug/kettle for boiling water for coffee and other purposes.  Indeed, why limit yourself – get all these items (if you don’t have them already).  None of them cost much more than $50 a piece at Costco or on Amazon.

Make a note of the power requirements for such items.

Everything Else – Okay, now we’ve covered the absolute essentials, but what else might also appear on a list of things you really need to be able to provide power to?  We’d certainly agree that you need to have half a dozen watts on hand for your phone charger, and maybe a few more watts for a radio or even a television.  For that matter, in the unlikely event that your internet connection is up, we’d not begrudge you the power cost of turning on your cable modem, Wi-Fi router and computer for an hour or two, a few times a day.

Maybe you have some medical equipment you need to operate.  And maybe you don’t want to have your generator running 24/7, and so have some batteries that you charge during the day and run your essential nighttime electrical circuits from at night.

Adding it All Up

Now that you’ve made a list of all the items you need power for, you’ll see there’s probably nothing on the list that needs to be receiving power, every hour, every day.  So this is where you now get to make a little bit of power go a long way.  You do this by letting your appliances take turns at the power from your generator.

For example, you know you’ll only need cooking appliances on a couple of times a day.  You also know that your fridge and freezer can go quite well for an hour or so (fridge) or half a day or longer (freezer) at a time with no power (especially if you keep their door shut!), and you also know that you can ‘play games’ with any heating or cooling, so that some of the day it is on, but some of the day it is not.

So what you should do is arrange it that you either have a cooking appliance, a fridge or freezer, or some hvac equipment running, but never all of these items at the same time.  How do you do that?  Simple.  Have plugs from all the devices sharing one (or two) sockets.  That way you can only have one item plugged in at a time.  Maybe you have some devices that would take up all the power, and three or four other devices that could run, any two at a time, and one or two devices that can be on or off at any time and it doesn’t really matter, because the power they draw is so low.

What you’d do is you’d have the output from your generator going first to a power strip that has all the small power devices connected to it, and one remaining socket.  You would have a collection of plugs next to this socket, and obviously only one of them can be plugged in at a time.  You might have a plug for your a/c, and another plug going to something else, and then one more plug that goes to a second power strip, on which you’ve blocked out all but two of the sockets, and you have a collection of plugs alongside that, so that any two of them can be connected at the same time.

That way it is physically impossible to overload your system, because the way you have your plugs and sockets lined up prevents that.

You can – and should – also have a power meter in series with all of this to monitor the actual power draw (see below).  Or perhaps manage all this with an Arduino based power management system.

Allowing for Surge and Starting Power

Most electric motors draw considerably more power when they are starting than when they are running at their normal speed.  This surge or starting power draw can be two or three times their running power – in other words, a 1 kW motor might have a surge/start power demand of 2.5 kW.  Some types of motors will draw as much as four, five or six times their normal running power while starting up.

This surge/starting power can last for as little as half a second or as long as three or four seconds, and starts off at the very highest level and then steadily declines down to normal running power at the end of the startup phase.

Most traditional generators will quote you two ratings – a rated or standard load, and a peak or maximum load.  So if your theoretical motor, with its 1 kW normal power draw and its starting power requirement of 2.5kW was to be matched to a generator, you should get one with a rated or standard load of at least 1 kW and a peak or maximum load of at least 2.5 kW.

But what say you have four devices, each of a 1 kW standard load and a 2.5 kW starting load?  Does that mean you need a 4 kW generator that can handle a 10 kW peak?  Happily, no.  It is normal to assume that you’ll never have multiple devices all starting simultaneously.  Because the starting load is so brief, and also quickly starts dropping down from maximum, this assumption is usually acceptable in most environments.  So in this example, you’d want a 4 kW generator with a 5.5 kW max load rating.

Choosing a Suitable Small Generator

Our expectation is that you’ll end up with a power need in the order of about 3kW; maybe a bit less, and if it is much more than that, you’ve failed to correctly differentiate between ‘need’ and ‘would like’!

The good news is that there are very many different models in this general power range to choose from.  But that’s also the bad news.  How to make a sensible buying decision with so many choices?

Well, there are a few things to consider that will help steer you in the right direction.

The first is that you want the generator motor to be four-stroke not two-stroke (ie separate oil and gas, rather than mixing the two together).  Four stroke motors tend to be more fuel-efficient and more reliable.

The second is that you want the generator to be as quiet as possible.  Some generators publish ratings on how noisy they are, but unfortunately there’s no universal standard for how this should be measured.  If you see a noise rating, it should be quoted in either dB, dBA, dBC, or possibly some other type of dB measurement.  It would be helpful to know if it was measured at full load, half load, or idle (there can be more than a 10 dB difference between idle and full load), and at what distance from the generator the measurement was made.  Was it in an open area or an enclosed room?  Was it a hard concrete floor or something more sound absorbing?

It is difficult to convert between the different type of decibel measurements, because the different weightings or adjustments that are implied by the letter A, B, C or D after the dB vary depending on the frequency of the sound being measured.  As a rule of thumb, though, the same sound probably registers lowest on the dBA scale, and slightly low on the dBC scale, and higher on the plain dB scale.  You’ll seldom/never see dBB or dBD.  Oh, to add to the confusion, some suppliers sometimes use the term dB and dBA interchangeably, even though they are actually very different.

You can sometimes get a sense for how loud generators are, even if they are not specified, by reading reviews on sites like Amazon.  Chances are someone will compare any given generator’s sound level to another generator, and then you can start to work from there to understand at least the relative loudnesses, and if one of the generators does have a published sound rating, then you know if the other one is above or below that figure.

A good generator has a sound level of under 60 dBA under at least half load when measured on a concrete floor from 7 meters (23 feet) away and with reflective walls 100 ft (30.4 meters) away, and with a very quiet ambient noise background (ie 45 dB).

Another relevant issue is fuel economy and run time.  These are two slightly different measures.  Fuel economy can be thought of in terms of ‘how many kWh of energy will this generator give me per gallon of gas it burns’.  An easy way to work that out is to see how many gallons of fuel an hour it burns, and at what load level.  For example, a 4 kW generator, running at 50% load, and burning 0.4 gallons of fuel an hour is giving you (4 * 50%) 2 kWh of energy for each 0.4 gallon of fuel, ie, 5 kWh per gallon of fuel.  The more kWh per gallon, the better.

The run time issue is similar but different.  It simply measures how long the generator will run on a single tank of gas.  Sure, the more fuel-efficient the engine, the longer each gallon of gas will last, but probably the biggest factor in run time is simply the size of the gas tank on the generator.  Run time means nothing when trying to get a feeling for gallons/hour of fuel use, unless you know how many gallons in the tank that are being consumed.

In theory, you should turn the generator off when re-fueling, and even if you don’t do this, it is always an inconvenient hassle, and so the longer the run time per tank of fuel, the happier you’ll be.

Make sure you understand, when looking at a run time claim, what the load factor on the generator is.  Needless to say, all generators will run much longer at 25% load than at 100% load.

One other nice feature, although one to be used with caution, is a 12V DC power outlet that might be suitable for some crude battery charging, depending on what its true output voltage might be.  But be careful – charging batteries is a very tricky business and perhaps it is more sensible to charge the batteries through a charge controlling device, and from the generator’s 110V main output.

An obvious consideration, but we mention it, just in case, is the generator’s size and weight.  The smaller it is, the easier it is to store somewhere convenient, and the lighter it is, the easier it will be to deploy when you need it.  Oh – do we need to state the obvious?  Don’t run a generator inside.  You must keep the motor exhaust well away from the air you breathe.

Something that is often underlooked or obscured is the quality of the a/c power and its waveform.  How close to a pure sine wave is the power that comes out of the generator?  This doesn’t really matter for resistive loads like a heater, but for motors and electronic circuitry, the ‘cleaner’ the wave form the better.  The only way to be certain about this is to connect the generator output up to an oscilloscope, but that’s not something that is easy for many of us to do.

There is a new type of generator now becoming more prevalent which not only has an excellent pure sine wave form of a/c power, but offers a number of other benefits too.


(Note – do not confuse an inverter/generator with a standalone inverter.  A standalone inverter converts DC power to AC power, typically from 12V DC up to 110V AC.  It does not have a generator connected to it.)

A typical generator (well, what we call a generator actually is a motor that runs an alternator) runs at a steady speed of 3600 rpm so that the power that comes out of the alternator will be automatically at 60 Hz (mains frequency).  The a/c waveform will be a little bit rough and noisy, which can be a problem when powering more delicate electronics.  Also, the engine is having to run at 3600 rpm, no matter if it is heavily loaded or very lightly loaded with power consuming devices because the frequency of the power generated is dependent on the speed of the motor.  This makes the motor noisier than it needs to be, and at lower power loads, makes it less efficient because it is using a lot of power just to spin itself around.  If the engine speed should fluctuate, so too will the frequency of the supplied power and that also can cause problems with electronic items.

Modern high quality generators take a different approach.  They generate a/c power at any frequency at all – it doesn’t matter what frequency, because they then convert the a/c power into DC power.  Then, in a second stage, they use an electronic inverter to convert the DC power into (at least in theory) a very clean pure a/c sinusoidal wave form at 110V.  You have a much nicer wave form, and because the generator can spin at any speed, the generator does not need to be so powered up if generating only a light load of power, making it typically quieter and more fuel-efficient (up to almost 50% more fuel-efficient).  On the downside, inverter/generators are currently more expensive, and have slightly more complicated electronics.  But for the type of application we are considering, they are usually vastly preferable.

Some inverter generators have a nifty feature.  You can double them up – if you connect the generator to another identical generator, using a special connecting cable that synchronizes the a/c output waveform of the two generators together, you can get twice the power.  You might say that it is better to have two 2kW generators rather than one 4kW generator, because that way, you have redundancy.  Anything could fail and you still have half your generating power.

Another nice thing about most inverter/generators is that they have been designed, right from the get-go, to be small, compact, lightweight, and quiet.  That’s not to say that they will be totally undetectable when operating, but they won’t be anything like as noisy as traditional generators that can be as loud as motor mowers, and if quiet operation is really important to you, some additional external baffling in the form of some sort of operating enclosure could drop the sound level down even further.

Their compact size and generally light weight makes it practical for them to do double duty not just as an emergency generator that gets ceremonially wheeled out of the garage when the power goes off (or, even worse, that resides in its own special building), but also as a go anywhere/take anywhere general purpose generator, useful for outdoors events, camping, remote building sites, and so on.

An obvious consideration for any generator is the cost.  With the constantly changing mix of models, ratings, and prices, we’ll not get too specific other than to observe that at the time of writing, it seems you’re likely going to be writing out a check for a little less than $1000 for a good inverter/generator with about a 3 kW rating, which is about twice what you’d pay for a regular generator without the inverter stage.  We expect this price differential to drop, but please don’t wait for that to happen before you get one!

Here is Amazon’s current listingof gasoline fueled generators.  Some are inverter/generators, others aren’t.  Some are California emissions compliant (CARB), others aren’t.

If we had to select a favorite, we’d probably nominate the Champion 3100W unit, or failing that, one or a doubled up pair of the Champion 2000W units.

How to Measure the Real Current/Power Used by Your Appliances

Devices such as this, costing $16 - $26, show you exactly how much power every one of your appliances consumes.

Devices such as this, costing $16 – $26, show you exactly how much power every one of your appliances consumes.

Maybe you have a computer with a 450 watt power supply.  Does that mean the computer actually is drawing 450 watts of power all the time it is on?  Almost certainly, not (a typical computer might consume only 50W of power, maybe even less, plus another 50W of power separately for its screen).  Maybe you have something else with a power rating plate on the back ‘110V 10A’ – does that mean it is drawing 10 amps all the time it is on?  Again, probably not.  A 10A rated device probably includes all lesser amounts of power too, and they simply put 10A on the plate as a conservative overstatement that wouldn’t cause them problems in the future.  (Note – resistive devices such as heaters tend to have more accurately plated power requirements.)

It is normal for appliances to show their theoretical maximum power draw rather than their normal power draw on their labeling.  While you need to leave a bit of ‘headroom’ to allow for occasionally one or another of your appliances peaking up higher to full power, it is acceptable to assume that most of the time, most of them will be using average rather than maximum power.

So how do you work out how much power your appliances are really truly drawing?  Easy.  There are devices that you plug in between the appliance and the wall, and they measure the power consumption of whatever is plugged into them.  Indeed, you don’t need to plug only one appliance into one of these measuring devices – we’ll sometimes plug a power strip into the measuring device, and then connect a bunch of equipment to it.

As you can see, Amazon sell such units for as little as $16.  Although there are some new low price units, we have always bought the only slightly more expensive Kill a Watt brand monitors.  You only need to get one to be able to work your way around your house testing everything.

In addition to showing you the instantaneous power usage, the Kill a Watt unit has another useful function – it can also show you total energy used over time.  When would this be useful?  Think of something that cycles on and off, such as your fridge.  You can measure how much power it uses when it is on, and you can guesstimate how much extra power to allow for when it first starts up, but how much power does it use per day?  Unless you stand over your fridge nonstop, day and night, carefully noting the minutes it is on and the minutes it is off, you’ll have no accurate way of knowing this.  But with the Kill a Watt meter, you simply plug the fridge in, check it is zeroed, then come back in a day or two and note the total hours elapsed and the total kWh used.  How easy is that!

(Note that if you are doing these calculations, you should check for different total energy consumption rates based on hot and cold weather, on opening the fridge a lot or a little, on placing hot foodstuffs into the fridge, and so on.  You’ll find that your daily average usage will vary enormously from some ‘good’ days to some not so good days.

How to Measure the Actual Power Being Provided by Your Generator

Your objective, much of the time, will be to run your generator at about 75% of full power.  At power levels much above this, or at power levels much below 50%, your economy will start to suffer and you’ll be getting fewer kWh of electricity per gallon of gas.

But how do you know how much power you are taking from the generator?  Easy.  Use the same Kill a Watt meter you used to calculate your power draws, and plug it into the generator then plug all power loads into a power strip plugged into the Kill a Watt.  That will tell you exactly the power you use.

You can use this information to know when you can add extra power loads to your generator, and when you are close to maxed out.

Two Notes About Fuel Storage

Many cities and many landlords have restrictions on how much fuel you can store at your residence, and probably also on the types of containers you can store the fuel in.  Sometimes these limits are per address, sometimes they are per building (which might mean you could keep fuel in a garden shed as well as in your garage and as well as in your house, too).

Enforcement of such bylaws is typically done ‘after the fact’ – ie, if you have a fire and it becomes apparent you had a mega-fuel dump in your garage, then you may find yourself being asked some awkward questions, not only by the fire marshal, but quite likely by your insurance company, too.  By the way, it is not always easy to tell, after a fire, exactly how much fuel was stored in each container, particularly if they were all in the one area.  It is probably possible to see how many fuel cans you had, but harder to tell which ones were full, which were half full, and which had only a couple of pints in the bottom.

It might pay to familiarize yourself with these requirements, and if you have a large number of half empty fuel containers, you better be sure you can explain why.

That also points to another benefit of a fuel-efficient low powered inverter/generator.  If you are trying not to trespass too far into ‘forbidden territory’ in terms of the fuel you store, then the more hours you can run your generator on a small amount of fuel, the better.

Secondly, gasoline (and most other liquid fuels) has a surprisingly limited life.  You can store it for three months with no ill effects, but after about six months, you’ll start to encounter problems.  Our article about fuel storage tells you more about these issues and also recommends the best form of fuel life extending chemicals.

Maintaining Your Generator

We hate internal combustion powered equipment, and avoid it wherever we can, particularly for things we only use rarely.  They can be difficult to store and unreliable in operation after extended storage.  Electrically powered items are generally very much better.

But in the case of a generator, you have no effective alternative to some sort of internal combustion powered device, and so you’ll need to be attentive to the manufacturer’s recommendations about periodic maintenance.  Not quite so clearly stated is the need to also be sensitive to the age of your fuel and managing that, so you aren’t running old untreated fuel in your generator.  Also not stated, but in our opinion very important, is to run your generator for several hours, perhaps once a quarter.  Solstices and equinoxes are the trigger dates we use for all sorts of maintenance items (other people use daylight saving start/end dates for things that need maintaining less frequently).

One other thought.  It might be useful to keep a spray can of engine starter fluid as a way of helping your generator come to life if it has been too long since it last ran and it is proving reluctant to start, particularly on a cold day.  Some generators start more readily than others.


A small, lightweight, and almost silent emergency generator can allow you to keep power on in your normal home, even when the lights are out all around you.  While we have nothing against larger systems that will power your entire home (and have one ourselves), if you’re not ready for a ‘full-on’ system and the costs and complications associated with it, a simple portable inverter/generator will give you enough power to make the difference between great discomfort and only moderate inconvenience.

These small units are also invaluable for apartment dwellers.

Jul 292013
Some people deride coal as being dirty, ugly, and old fashioned.  They are foolish to do so.

Some people deride coal as being dirty, ugly, and old-fashioned. They are short-sighted to do so.

It is only slightly an exaggeration to say that coal has fueled and been a significant enabler of much of the modern world’s development.

But these days, ‘conventional wisdom’ denigrates coal as being dirty, environmentally unfriendly, and generally nasty.  The popular perception (which is completely wrong) is that the US (and possibly world-wide) coal industry is in terminal decline, because it is an obsolete and no longer effective/useful energy source.

Is there actually any continued role for coal in the future – either in our ‘normal’ future or WTSHTF?  Due to the prominence of coal for much of our past, that is a question we need to research and resolve.  So, please keep reading.

Historically, coal has been a long time and low-tech energy source, being reasonably easy to mine, to transport, to store, and to use.  Any low-tech energy source becomes very relevant to us when we consider a future where our high-tech infrastructure may have failed.

Coal has been used for hundreds if not thousands of years in homes, then subsequently as a fuel for stationary boilers in factories, then as a fuel for steam ships and steam locomotives, and as a feedstock for gasworks making city gas supplies, and as an energy source for power stations, and even as a raw source for hydrocarbon products of all sorts.  As recently as the mid 2000s, more than half of our nation’s energy came from coal-fired power stations.

In times of oil scarcity, coal has been used to make ‘artificial’ petrol and other liquid fuels.

Coal is also used in the production of steel, cement, even paper, and many other things.  The US is the world’s second largest coal producer and has the world’s largest reserves – more than 240 years of supply.  So coal would definitely seem to be something all preppers should consider.

As preppers, our major focus on coal would be as an energy source.  The good news is that coal is a very good value source of energy, less than half the cost of most other major energy sources.

There are very many different ways to measure the costs of energy, but the disparity between the cost of coal and other energy sources is so huge as to make it unnecessary to quibble over the last few percents.  If you look at the table on page 3 of this document, you’ll see the following costs per million BTUs of energy for a range of different energy sources (2010 data averaged across the US).

Energy Source Cost ($ per million BTU)
Coal $2.42
Natural Gas $7.41
(note – prices in 2013 are about half this)
Distillate Fuel Oil $20.62
Jet Fuel $16.28
LPG $19.61
Motor Gasoline $21.98
Residual Fuel Oil $11.70
Other $17.97
Average for all Petroleum $20.32
Nuclear $0.62
Wood and waste biomass $3.45
Electric Power Industrial $2.62
Electric Power Retail $28.92
National Average $18.73


As you can very clearly see, and based on these wholesale/industrial rates, nuclear power is massively better value than any other power source, but coal comes second, followed closely by wood.  Natural gas is three times the cost of coal, LPG and gasoline are about eight times the cost.

So, in terms of theoretical cost per theoretical unit of energy, coal is massively better than all other energy sources open to us, both now and in the future.

Another interesting point is that one ton of coal can create two barrels of oil.  At the time of writing, this regularly updated coal price report shows coal varies in price from as low as $10.30/ton to as high as $68.25/ton.  To put this number into clear perspective, even after allowing for carbon capture and other ‘best practice’ environmental considerations, it costs less than half as much to convert coal to oil than it does to buy a barrel of oil directly (here’s an interesting report on that topic).

We point this out not to suggest we all create Fischer-Tropsch plants to convert coal into oil in our back yards, but merely to open your eyes to the enormous potential of coal for many different energy applications, both at present and in the future.  It is very wrong to think of coal as ‘old fashioned’ (and as ‘bad’).

If the preceding is even half-true, why don’t we all build massive coal bunkers and store tons of coal?  Sure, it is true that coal is not a very ‘clean burning’ energy source, but who would worry about that after TEOTWAWKI, when all sources of industrial pollution with have been close to zeroed out?  Let’s learn some more about coal.

Different Types of Coal

As you might have noticed from the coal price report linked in the preceding section, the amount of energy you can get from a ton of coal can vary widely, as do other factors such as its sulphur content.  Here’s an interesting chart that sets out the varying amounts of sulphur and energy from coal in different parts of the US.

The wide range of different properties of coal have been categorized into four broad categories (and there are sub-categories within each of these four main categories).  The ‘best’ coal for most purposes is generally anthracite, followed by bituminous, sub-bituminous, and finally lignite type coal.

Anthracite has the highest calorific (energy) value, the highest carbon content, and is the oldest coal.  Each of the three subsequent grades have less energy, less carbon, and are more recent (albeit in geological terms of hundreds of millions of years).

The subbituminous category is of interest, even though it would seem to be the third of the four grades, because it has a low sulphur content.

Using Coal

Coal burns hotter than wood and can create more soot.  If you are going to burn coal in your house, you’ll need to make sure that your fireplace and chimney system can handle the greater heat of coal.

Coal also needs a different type of air flow than does wood.  You need to have coal on a grate with air able to come in from under the great and go through the coal bed for its combustion.  This is fairly critical – a solid bed of coal (as may happen after some hours of burning and a layer of ash being created) will prevent air flow and proper combustion; whereas too porous a bed will also fail to allow for optimum burning.

A well tuned coal fire should generate little smoke, although that depends a bit on the type of coal being burned.  Typically anthracite is preferred for home use and it is a ‘clean’ burning coal.

Coal comes available in different size ranges.  Here’s a list from small to large, and with sizes (which seem to vary from place to place somewhat)

  • #5 (typical size 3/64″ x 100 mesh)
  • #4 (typical size 3/32″ x 3/64″)
  • Barley (Buckwheat #3) (typical size 3/16″ x 3/32″)
  • Rice (Buckwheat #2) (typical size 3-5/16″ x 3/16″)
  • Buckwheat (typical size 9/16″ x 3-5/16″)
  • Pea (typical size 13/16″ x 9/16″)
  • Nut (typical size 1 5/8″ x 13/16″)
  • Stove (typical size 2 7/16″ x 1 5/8″)
  • Egg (typical size 3 1/4″ x 2 7/16″)
  • Broken or lump (typical size 6-8″ x 4″)

We’ve seen people express opinions favoring one size over the other, and others favoring quite the opposite (for example here), and the best size probably depends on the type of stove/furnace and grate you are using.  If you are using an auto-stoker device, then size becomes even more relevant.  Suggestion – experiment to start with, using different sizes until you find the size that works best for you.

As with any type of combustion indoors, we’d recommend you have a couple of CO detectors to keep an eye on CO levels, just in case unusual conditions interfere with the normal safe operation of your fireplace/stove.  You should also have a fire extinguisher or two, and perhaps a bucket of sand (or baking soda) as an excellent way of damping down a coal fire if it starts to get out of hand.

We’d also suggest you regularly inspect your flue/chimney setup for any ash accumulation and sweep it clear as needed.  After a while you’ll get a feeling for the needed frequency of maintaining this – failure to do so might interfere with the venting of the fire and cause dangerous gas buildups inside your house, and/or might encourage chimney fires.

Of course, if you change your coal type, you’ll need to ‘recalibrate’ your expectation of how regularly you need to clean your flues.

Real World Costs and Benefits

We were earlier quoting the wholesale costs of different energy sources.  As you can doubtless guess, there’s a world of difference between the ex-mine cost per pound of buying 1,000 tons of coal, and the cost of having one single 50 lb bag of coal delivered to your doorstep.

Here’s a very useful fuel comparison calculator you can use to compare the respective costs of different energy sources for home heating.  It comes with some default numbers that aren’t enormously out of line, but adjust them for the actual costs you’d pay in your area, and you’ll get a clearer view of the actual costs and benefits of different heating sources.

Coal’s benefit reduces somewhat when you’re buying coal in small quantities, but it typically still shows some advantage over most other heating options.

Read More in the Second Part

This was the first part of a two-part article on coal.  Please now click on to read the second part of the article – Practical Issues to Do With Using Coal.


Jul 292013

We love coal fires and their distinctive appearance and smell.  The fact they are a very efficient and low cost way of heating is a further reason to consider coal as a fuel source.

We love coal fires and their distinctive appearance and smell. The fact they are also a very efficient and low cost way of heating is a further reason to consider coal as a fuel source.

If the concept of coal as a fuel source appeals, you need to shift from the theory to the practicalities of what it will cost to buy the coal, how you will store it, and other related issues and considerations.  Our earlier article, ‘Coal – A Prepper’s Friend of Foe‘ looked at the overall issues to do with coal, this article looks at some further specific things to consider when evaluating coal.

Where the Coal Is and Buying It

Clearly the closer you are to a coal mine, the lower your cost of coal will be, although another factor will be the ease of shipping coal to your location.  Here’s a somewhat dated but still accurate map showing the spread of coal fields across the country, and here’s a link to the latest US Energy Information Annual Report on coal which has details of mines and their production levels and much more.

If you are wanting to buy significant amounts of coal, then you could consider buying full rail wagon or truck loads.  A full truck load is about 24 tons.  But if you are wanting more moderate amounts (especially to start with when you might be experimenting with different sizes and grades of coal to see what works best with your setup), you should find the closest possible coal merchant.  If you can’t find any nearby coal merchants, you could contact the closest coal mines and ask them for referrals.  Of course there are online services such as this and this too (but we’ve yet to see Amazon start selling it complete with free second day delivery included!).

However, please wait a few minutes before rushing to buy some hundreds of tons of coal.  You should read on to the next section.

The Downsides of Coal

There are two major problems (as well as some minor problems) with coal that argue against our broad adoption of a coal strategy for our future energy sources.

The first is that burning coal is harder on our furnaces than burning wood.  The sulphur that is present in coal creates compounds that attack the metal of our stoves, fireplaces, chimneys, and other structures.  This is nothing that can’t be reasonably compensated for when designing and building such structures, but it does accelerate the wear on all such things, compared to burning wood or natural gas or fuel oil.

The second major problem is storing coal.  Now, you might think that a natural unrefined substance such as coal, which has been slowly forming for 300 million years, and which you may also know is fairly hard to set on fire and to keep burning, would last another few million years without any problems after taking it out of the ground, but if you thought that, you’d be surprisingly wrong.

Coal can be a potentially troublesome product to store.  It reacts with air and with water, and the result of the reaction causes a release of heat.

The release of heat does two things.  First, it speeds up the reaction (making for a positive-feedback loop), and secondly, if it builds up sufficiently, it ignites the coal.  So you can have a pile of coal, even in a cool and/or damp environment, that sets itself on fire.  Amazingly, and completely counter-intuitively, spraying a pile of coal with water can increase the chances of it self-combusting.

Coal not only burns spontaneously after it has been mined, it can also do so while still in the ground; indeed, according to this article, thousands of coal fires are burning all around the world, all the time.  Coal fires in China burn through 120 million tons of coal every year, and contribute 2% – 3% of the total annual worldwide CO2 emissions from fossil fuels.

Coal fires in stored coal piles are far from uncommon, and take very little time to start (75% of such fires start within three months of a coal pile being formed, and many of those fires within the first two weeks).  A little known fact about the Titanic is that when it put to sea on its maiden voyage, it had a fire burning in its number six coal bunker.

If you have large-sized piles of coal, you need a way to monitor their core temperatures.  If the core temperatures reach 140°F, then you need to consider preventative measures, and by the time it gets to 150° it is time to break the pile and allow the coal to cool before repiling it.  Coal generally will start to smoke at about 180°, and at that point, it is a bit too late because it is starting to combust.

Note that coal will often steam as water dries off, this is different to smoking.

Large lumps of coal are more resistant to spontaneous combustion than smaller lumps, and anthracite is the least susceptible, while lignite is the most susceptible.

If there is a lot of air flow through the pile, that will keep the coal cool.  If there is no air flow through the pile, that will keep oxygen away from the coal and limit the reaction.  But somewhere in the middle, between ‘no air’ and ‘lots of air’ is a danger zone with enough air to encourage spontaneous combustion.  It can only take a small amount of air flow for this to occur.

So, if you are storing coal, you need to keep the piles small and monitor their core temperatures.

A related issue is that coal deteriorates over time.  It again seems strange that something which is formed so slowly over 200 – 300 million years is so apparently ‘unstable’, but you will definitely start to notice reductions in heat output from coal that has been stored for extended periods of time.

These heat output reductions are probably not profoundly significant, and you can still store coal for many years, even tens of years, and still get valuable energy from it, and when you compare this to storing wood (which might rot) and liquid fuels (which need stabilizer and even then have a maximum storage life of perhaps ten years) it is clear that coal is as suitable for storing long-term as other energy sources.  But it isn’t perfect.

Legal Restrictions on Burning Coal

Another problem might be any clean air regulations in your state/county/city that restrict your ability to burn coal.  The problem is that such laws almost certainly don’t say ‘except in an emergency when you can burn anything you like at any time for any purpose’.  If the law says it is illegal to burn coal today, it will still be illegal to burn coal WTSHTF, and while enforcement might be thin, sooner or later some enterprising person will realize you are burning coal and will use the law as an excuse to legally ‘fine’ you, with the fine perhaps being the forfeiture of your remaining coal or food or anything else they wish it to be.

On the other hand, if your region just has occasional, weather/air quality dependent burning bans, then perhaps, after TSHTF, the authority that rules on such things will no longer function, and/or, the lower level of general industrial activity will reduce the number of times during the year when coal is banned.

Clearly if you plan to rely on coal as a year-round fuel source (eg firing a boiler that then provides heating, hot water, and possibly even electricity generation or a mechanical power source) you need to be sure you can legally use it year round.

How Much Space Does a Ton of Coal Take Up?

So, if you do decide to set aside space to store coal in bulk, how much space will you need?

Our first comment is to remind you of the problems outlined in the preceding section to do with coal’s propensity to spontaneously self-combust.  It is better to have a number of smaller piles/bunkers/whatevers of coal than one large one.  If nothing else, we’d want to be sure that nowhere in our fuel pile was more than four feet from the outside.  That might sound like a restrictively small size, but you could get as much as 6 tons of coal in such a pile.

This is a very conservative suggestion, but better safe than sorry.  Back in the 1920s, the Railroad Administration suggested piling coal for railroad storage not over twelve to fifteen feet in height when the track is placed on top of the coal pile, and not over twenty feet when a locomotive crane is used.  The Home Insurance Company advised against piling in excess of twelve feet, or more than 1500 tons in any pile, and suggested trimming the piles so that no point in the interior was more than ten feet from an air-cooled surface.

Coal is dense, but due to its irregular size and shape, it doesn’t pack efficiently.  In general, you can expect to get from about 43lbs to 59 lbs of coal per cubic foot.  Because coal is heavier than water, wet coal takes up more space for a given amount of weight than does dry coal.  Older coal (ie bituminous or anthracite) will have a greater weight of coal per unit of volume than does newer coal.

So, back to our suggestion you keep a coal supply in piles measuring 8′ x 8′ on their base and 4′ high – a total of 256 cu ft.  If you work on say an average of 50 lbs of coal per cu ft, that would be about 12,800 lbs of coal, or 6.4 short tons per pile.  You are using 10 sq ft of floor space to store a ton of coal.


This was the second part of a two-part article about coal.  If you’ve not already done so, you might choose to now read our first part, ‘Coal – A Prepper’s Friend or Foe‘.

Coal is usually the second cheapest energy source in the US today.

The two cheapest sources of energy in this country are strangely the two which ‘greenies’ hate the most – coal and nuclear.  On the other hand, arguably the ‘cleanest’ source of energy is also the most expensive (electricity) and being as how almost half of all electricity comes from coal fueled power stations (and most of the rest from stations burning either natural gas or oil) the ‘cleanness’ of electricity relates only to what you see coming out of the wall rather than the total process of generating the power in the first place!  But it isn’t our place, here, to get into a discussion on the illogic that surrounds too much environmentalism….

Suffice it simply to say that while it is of course entirely impractical to consider building your own personal nuclear power plant; depending on where you are, where you could source coal from (and at what cost) and any local restrictions on burning coal, you might find coal to be a surprisingly cost-effective and good solution for much of your future energy requirements.

If you do choose a coal based approach to some of your energy needs, you are well advised to choose specific stoves/furnaces that are designed and optimized for the different burning characteristics of coal (compared to wood).

We’d recommend you research the issues to do with using coal at your retreat.  You might be surprised at how positive a coal based energy approach could be.

Here’s an interesting reader forum type website that could be a good resource for preppers wanting to find out more about buying, storing, and using coal.

Jun 042013
When the grid goes down, we will not only need to generate our own electricity but we'll need to store it too.

When the grid goes down, we will not only need to generate our own electricity but we’ll need to store it too.

In our amazing modern life, we seldom pause to consider all the ‘behind the scenes’ miracles that are being worked for our benefit – all the things which could fail, might fail, and probably will fail in a Level 2/3 scenario.

Of all these blessings that we take for granted, perhaps none is greater than the miracle of electricity.  For most of us, nearly all the time, we can plug anything into any wall socket in our house and it will operate, and we can turn on any or all of our appliances and enjoy their normal operation, at any hour of the day or night.

Electricity from our local utility company is always available and amazingly inexpensive and probably has been the greatest lifestyle enhancer of the last 100 years.

You mightn’t think electricity to be amazingly inexpensive when seeing your monthly bill, but try going without electricity for a week or two then ask yourself ‘how much would I pay to get my electricity back?’ and then you’ll appreciate its value.  Or cost out other ways of creating the electricity – for example, electricity from a high-efficiency diesel generator will probably cost 40c per kWhr, compared to a typical cost of about 10c for mains provided electricity.

When the grid goes down and you have to generate your own electricity, you’ll quickly build an even greater appreciation of how amazing our present electricity supply is.  No part of generating electricity in the future will be easy, and because you’ll be using a different way of generating much/most/all of your electricity, one issue deserves particular mention – something you’ve never needed to think about in normal life (although in actuality, it is something the utility companies are very sensitive to).

The chances are you’ll make use of photo-voltaic cells – PV cells or solar cells – for at least some of your energy needs.  Maybe you might use of wind power, too.  These are great energy sources, but there’s an associated problem.  This is the start of a four-part series of articles that considers this problem, and offers ways to optimize your work-arounds and solutions.

The Need to Match Electricity Demand to Electricity Supply

The problem relates to a major limitation of both your likely future energy sources.  In the case of PV cells, you know they only work when there’s reasonably bright sunlight.  So, you never get any power at night, and on short winter days that are overcast, you get very little power even in the middle of the day.

In the case of wind power, the wind turbine only generates power when there is ‘good’ wind – nice steady smooth wind blowing in a reasonably consistent direction at a reasonably consistent speed (wind gusts can destroy a turbine) that is neither too fast (at high speeds, turbines stop working to prevent damage) nor too slow (turbines have a minimum speed below which they no longer generate useful amounts of power).

The problem with both PV cells and wind turbines is that you can’t match their power generation to meet your requirements.  A diesel generator simply starts working harder (and burning more fuel) when its load increases, and if you have a micro-hydro station, you can vary the amount of water driving the turbine, but there’s no way you can make the wind blow more strongly or the sun shine more brightly.

The typical solution is to have a PV/wind system that provides enough power during a realistic typical sort of day of working to both cover your power needs during the period of operation, plus surplus power which can be transferred into some sort of electricity storage system.  Then, when the power being generated becomes insufficient to meet your requirements, you can switch to the stored power and use that until such time as the primary power source can start meeting your needs again.

Hence the need to store electricity.

Storing Electricity is Not Always the Best Solution

In addition to whatever method of storing electricity you might choose to match with your renewable electricity generation program, there is another way of storing electricity which has a huge plus but also a huge minus.

We are talking about simply keeping a large supply of diesel or propane for a generator.  Each gallon of diesel can give you about 10 kWhrs of electricity, and with a typical house using about 1000 kWhr of electricity a month (depending on design, size, and climate of course) at present (with plentiful energy, low-cost, and no need to fanatically conserve energy) this suggests a diesel generator would consume about 100 gallons of diesel a month to give you all the electricity you need.  A few tweaks to your retreat design, some more insulation, and some alternative heat and energy supplements, and you could easily halve this to 500 kWhr of supplementary electricity per month – a mere 50 gallons.

If you have 1,000 of diesel stored, that could see you through 20 months of power needs, which would cover all Level 1 and most Level 2 scenarios.  Those 1,000 gallons of diesel represent something well under $10,000 to purchase, to stabilize with fuel stabilizer for many years, and to store in good quality long life tanks.

As a comparison, if you wanted to have a battery based electricity storage capacity of say 75 kWhr, you’re looking at an investment in batteries and control circuitry of $20,000 or more, and you’ll want to significantly expand the power output of your solar or wind setup so it has sufficient extra capacity not just to meet your regular needs but also to charge up the storage banks – maybe something like an extra 5 kW – 10 kW of power generating capacity – figure on another $10,000 or so for that.

So for solutions extending out a year, two, maybe even three or four, you might decide not to overcomplicate things (and add to the cost as well) and have a system that provides renewable energy during the day and relies on a diesel generator at night.

But, having said that, a key part of preparing includes planning not just for Level 2 situations, but also for ultimate Level 3 situations, and if you base your electricity generation on diesel, you know that, sooner or later, you’ll run out of diesel.  So if you wish to be best prepared for the future, you’ll recognize that electricity storage, while not necessarily the most economical solution for Level 2 events, is essential for Level 3 preparedness.

Any type of preparing of course ideally involves multiple solutions to each single problem, so as to have redundant approaches, and for this reason too, it makes sense, even in planning for shorter term problems, to have at least some way of storing some electricity.

How to Store Electricity

It is difficult to store electricity, with the only ‘true’ form of electrical energy storage being a device known as a capacitor.  While capacitors are remarkable and very useful in some applications, they are sadly not really well suited for storing the large amounts of energy we wish to store, and for the lengths of time we wish to store it.

We’ll spare you the science, but suffice it to say that all other forms of energy storage involve using the electricity to create a different form of energy which can be conveniently stored and converted back to electricity again in the future.  Even a battery, which might seem to be a pure store of electricity, actually converts the electricity to a chemical form of energy.

In considering an electricity storage method, you need to consider a number of factors :

  • System efficiency – for every kWhr of energy you put into the system, how much do you get back again when you convert it back to electricity again?  In the broader scheme of things, efficiency is of course important, but in this application, where you’re essentially storing spare/surplus power, it isn’t quite as important as it would be, for example, for a utility company that is paying for all the electricity it generates and seeking a way to cover the ups and downs of daily demand.
  • Storage losses – does the stored energy slowly – or quickly – dissipate over time, or does it stay unchanging for long periods of time?  In our case, we will have a mix of requirements – some energy needs only be stored for 15 hours or so (ie from when PV cells stop providing power around sun-down until they start again shortly after the next dawn).  But you will want to be able to store some energy for a longer term in case of extended periods of insufficient power supply during the day.  Storage losses are an important factor.
  • Size and other requirements – is anything special needed?  Does the storage thing take up a lot of space?
  • Maintenance and useful life – how many times can electricity be transferred in and out of the storage system?  What types of ongoing maintenance are required, and how easily can the system be maintained in a future situation where you’ll not have high-tech equipment, and sooner or later will run out of replacement spare parts?  How many years until it fails entirely and needs to be replaced?  Clearly these are very important issues for us.
  • Capacity – how much electricity can be stored in the system?  Are there limits to its ability to grow?  Of course we need to have adequate capacity – that goes without saying, and if there’s a low tech way we can grow the system in the future, so much the better.
  • Cost – what are the costs of storing electricity in the system?  Do we need to comment on the fact that, as preppers, we are always confronted with too many different high priority ways to invest our money and insufficient money to invest!

Although there are very many different ways to store electricity (perhaps better to say ‘to store energy’ because the thing we are storing is not actually electricity, but something else which can be converted into electricity), in our case there are only one or two which are practical to the size, scale, budget, and other requirements we are likely to have.

The most obvious storage system involves batteries – probably some sort of lead-acid batteries.  A less obvious form is to store energy in a rapidly spinning flywheel, and a third approach, which may work well for some people but not well for others, is to store energy in the form of pumping water up to a higher elevation, and then to reclaim it as needed by having the water flow down through a micro-hydro power generator.

Continued in Part Two

Please now click on to read part two of this series, ‘Using Batteries to Store Electricity‘, and then continue on to parts three and four (Other Energy Storage Methods and Strategies to Reduce Your Need to Store Electricity).

We also have other articles on the general topic of Energy.

Jun 042013
A cutaway view of a typical lead-acid battery.

A cutaway view of a typical lead-acid battery.

This is the second part of a four-part article series about how to store electricity (better thought of as storing energy rather than electricity per se).  If you arrived directly here from a link or search engine, you might wish to start from the first part of the series here, then read on sequentially through this article and the balance of the series.

Lead-acid batteries use a technology that has been around since the mid 1800s.  The relatively recent Lithium-ion technology is showing some signs of promise as a possible replacement to lead-acid, but that is still a way off, and for now, for our purposes, lead-acid batteries, while far from innovative, remain probably the best general purpose way to store electricity in circumstances that typical preppers are likely to encounter.

Batteries offer between about a 50% and a 85% efficient means of storing electricity, making them neither particularly better nor particularly worse than most other forms of storing electricity.  They have acceptably low storage losses, typically losing somewhere between 2% – 15% of their charge each month.

As old-fashioned as they may be, the generic concept of lead-acid batteries masks the fact that there are many different types of lead-acid batteries, designed for different purposes, and with greatly varying suitability for our requirements.

They also have a surprisingly complex series of requirements for how to charge and maintain them so as to get the optimum life out of the batteries – to prolong the amount of electricity they will store, to maximize the number of charge/discharge cycles they can withstand, and to protect against sudden failure.  For optimum use, it is important to be sensitive to many aspects of their care and conditioning that we never consider with our car battery – and the proof of the need to look after our storage batteries should be evident when you consider how quickly car batteries fail!

Lead-acid batteries fall within three general families when it comes to how they are made.  The oldest technology is the ‘wet’ or flooded type battery, then there are gelled batteries and AGM (Absorbed Glass Mat) batteries.  Flooded batteries typically have removable caps and you should occasionally check the level of the liquid inside the cells, adding distilled water as necessary, although some now have ‘fully sealed’ cells (which actually aren’t fully sealed).  AGM and gel batteries are always sealed and in theory need no maintenance.

Some people view gel cells as a transitional technology and suggest you avoid them, preferring either AGM or wet cells.  Gel cells require different charging procedures and voltages than regular and AGM batteries, and are more prone to degradation or failure if not treated optimally.  AGM cells are very low maintenance, but more expensive for the same amount of capacity as wet cells.

The most common measure of a battery’s storage capacity is how many amp-hours of charge it can give.  However, it is important to appreciate that the amp-hour capacity of a battery is dependent on how fast it is being discharged.  The slower the rate of discharge, the more total charge the battery will give you.  For example, a battery that is discharged evenly over 20 hours will typically give 10% less charge than a battery discharged over 100 hours.  A battery that is discharge over 8 hours will typically give almost 20% less charge than one discharged over 20 hours.

Our point is that it is important to understand whether a battery’s capacity is being measured on the basis of a 100, 20 or 8 hour discharge rate.

The lead-acid battery that most people are most familiar with is a car starting battery.  This is designed to store a small amount of charge which can be provided at a very high rate of current for a short period of time, for the purpose of starting the engine.

It has a secondary purpose to power the car’s various electrical loads for a moderately short amount of time while the vehicle is stopped and the engine switched off.

But these batteries are not designed to give up all their charge over a slow gradual period; indeed, they’re not designed to give up all their charge at all.  They are not ‘deep cycle’ type batteries.  Perhaps because of this, they are typically not even rated in terms of amp-hours of storage, but rather quote a ‘cold cranking amp’ current rating – the amount of current it can supply when being called upon to turn a vehicle’s starter motor.

Don’t use car batteries as storage batteries.  They are not designed for deep discharging and don’t last long.

No lead-acid battery should be fully discharged before recharging it again.  The greater the amount of discharge before recharging, the more the battery is stressed and the shorter its future life will be, in terms of additional charge/discharge cycles and capacity of charge that can be stored per cycle.

Deep cycle batteries are designed to allow for the greatest amount of charge depletion per cycle.  Typically these types of batteries (sometimes referred to as ‘golf cart’ or even as ‘forklift’ batteries) are designed to give up perhaps 70% of their capacity per discharge without suffering any severe consequences.  Some batteries allow for an 80% discharge, but it is probably better to go easy on them and not go all the way down to 80%.

Depending on the exact battery design, discharging to 50% is considered the ideal compromise, and you should avoid discharging beyond about 70% of capacity.

You can measure the state of charge of a battery either by testing the specific gravity of its liquid, or by testing the voltage it puts out.  The specific gravity measurement is slightly more accurate, but with so many batteries either sealed or AGM, these days most people use voltage readings as a measure of charge instead.  The voltage steadily declines as the battery discharges, starting from 12.6V when fully charged.  Am offload reading of 12.3V shows about a 50% charge, and a 12V reading (offload) more or less corresponds to a 75% discharged state.

Battery life also depends on other factors such as even ambient temperature (cooler is better than warmer).

Modern batteries such as these or these claim to give up to 2000 or so cycles, with discharge all the way to 80% each time.  That’s almost six years of daily discharging (or twelve if two-daily discharging, and so on for extended cycles).

In terms of actual elapsed time, these types of batteries seem to be talking of lifetimes in the 10 – 20 year range, if the number of cycles isn’t exceeded in a sooner time frame.  That’s starting to become a viable life.

Other highly respected battery suppliers include Concorde/Lifeline and Rolls/Surrette.

If you are building a high-capacity battery, there are several ways to do this to best effect.

The first is not to use a 6V or 12V based system.  Increase your voltage (by connecting batteries in series) to 24V or 48V.  This has several benefits, including reducing the electrical losses through your wiring and/or reducing the need for ridiculously oversized wiring to carry your battery current.

The second is of course to connect multiple batteries in parallel, but this needs to be done with caution.  The more batteries in parallel, the greater the chance that a ‘bad cell’ in one battery unit will bring down the entire set of batteries.  What happens is the battery with the higher voltage then starts ‘charging’ the battery with the lower voltage, and bleeds away its power into the weaker battery.

For this reason, it is always important to match batteries with like batteries, whether connecting in parallel or serial – batteries of similar capacity and similar state of life.

It is best to arrange for each individual battery in your battery array to be of as large a capacity as possible.

Beyond that, rather than to create one huge battery with maybe six individual batteries paralleled together, it is much better to create two three battery units, or even three battery units, each with two paralleled batteries.  That means you can better rotate your batteries in and out of service, alternately charging and discharging each battery in sequence, and stretching out the overall life of all the batteries.

Continued in Part Three

Please now click on to read part three of this series, ‘Other Energy Storage Methods‘, and then continue on to part four ‘Strategies to Reduce Your Need to Store Electricity‘.  If you’ve not yet done so, you might wish to also read the first part of the series, ‘Storing Electricity‘.

We also have other articles on the general topic of Energy.

Jun 042013
The fickleness of wind and other renewable energy sources means you need to store power as best you can when it is available, for future use when it is not available.

The fickleness of wind and other renewable energy sources means you need to store power as best you can when it is available, for future use when it is not available.

This is the third part of a four-part article series about how to store electricity (better thought of as storing energy rather than electricity per se).  If you arrived directly here from a link or search engine, you might wish to start from the first part of the series here, then read on sequentially through the balance of the series.

Flowing Water Uphill and Other Gravitational Energy Stores

Another interesting approach to storing electricity is by pumping water uphill.

If you have a hill on your property and sufficient water, you can use surplus energy to pump water up to a large reservoir on the top of the hill, and then when you need electricity, you run the water down the hill and to a hydro-electric plant at the bottom.

This can store energy for a longer term – the only storage loss being evaporation – but involves potentially massive amounts of water and as much vertical rise/fall as possible.  If you double the height differential, you halve the amount of water you need, and vice versa.

Although this might seem like an unusual and strange technology, 93% of all stored power, world-wide, is stored this way.

To put the amount of water needed into perspective, if you wanted to store enough water to be able to generate 5kW for 100 hours – a good reserve for emergencies) you could either have an efficient diesel generator and about 50 gallons of diesel, or if you were able to store water somewhere 100 ft higher than ground level, you’d want to have about three million gallons of water in the reservoir.  That is about 400,000 cu ft of water, so think of a pond measuring perhaps 200 ft by 200 ft and 10 ft deep.  You’d also need another storage area at the bottom to hold the water prior to pumping it back uphill again.

This is of course not impossible, assuming you have a way to get the vertical rise that is necessary, and a source of water to replenish losses from evaporation.

The concept can be extended and slightly modified, indeed, it is merely an extension of the concept found on many cuckoo clocks, where a weight slowly descends, driving the clock mechanism, then is ‘rewound’ when you use energy to pull the weight back up again.  Anything that uses gravity as a way of storing energy can work.

There is a project currently being developed in California that uses rail boxcars loaded with heavy gravel.  Electric locomotives use spare grid power to haul the boxcars up a length of steeply inclined track, and then when the electricity is needed to be returned to the grid, the boxcars are allowed to push the loco down the track, and the loco now acts as a generator feeding power back into the grid.

Such a system can be 80% or more efficient, and will store energy indefinitely with no storage loss.  The boxcar example requires more power to push the boxcars uphill than would be available from a typical private power source, but this could of course be modified (lighter boxcars and/or less steep grade).

These types of systems can require a fair measure of space.  In the water example, if the water reservoirs at top and bottom are ten feet deep, you need almost 2 acres of space just to store the water, plus more space for the pipes and generator/pump.

But their biggest requirement is the height differential.  If you’ve got a fully flat property, you’re either going to have to create a raised portion, which would involve a prohibitive amount of earth working, or else look for other alternatives, which presently tend to invariably circle back to batteries.

Using a Flywheel to Store Electricity

Flywheel technology is becoming more practical, although still a technology that is equal parts experimental and/or not ideally suited for our applications.

With a flywheel, spare electrical energy is used to spin up the flywheel – a huge heavy massive device that spins rapidly – and then when electrical energy is needed, the flywheel is used to run a generator.

Flywheels can store surprisingly large amounts of power, and if in a near vacuum and with magnetic bearings, are slow to lose their energy (by ‘slow’ we mean the energy loss rate is acceptable for a device that charges during the day and discharges at night, but not quite so acceptable if you want to be able to store energy for several days).  They can provide a reasonably efficient means of storing power.

They are also fairly low maintenance, especially if kept in a semi-sealed environment.  But they are also large heavy devices, potentially weighing 5 – 10 tons or more, and require very precise balancing and bearings due to the speeds they spin at.

Flywheels are best suited for applications that require large amounts of sudden energy and/or applications that have large amounts of energy suddenly surplus.  That’s not to say they’re not potentially good for our sorts of applications too, and the good news is that the growth in renewable energy generation is feeding growth in related issues, particularly energy storage.

We expect to see small-sized flywheel installations continue to be developed to a point where they may become practical for storing energy for short-term overnight use, but we’ve not encountered a flywheel that is quite ready for prime time just yet, alas, although there are some hopeful developments underway at present.

There are many other technologies that are either in a development stage, or which are not suited for our sort of scale of energy storage – for example, compressed air.

How Much Electricity Storage Do You Need

Storing electricity is a somewhat wasteful and somewhat expensive process, although it could be convincingly argued that having extra spare electricity being unused at certain times of day to also be wasteful too!

Some electricity storage is both prudent and essential.  The question becomes – how much.

If your only renewable energy source is PV, then you need enough for two purposes :

First, you need enough to get you through a typical night from when the energy flow from the cells diminishes as the sun gets low until such time as the energy flow restarts when the sun rises the next morning.

Second, you need additional ‘spare’ capacity to cover times when the weather is bad, the sky is full of clouds, and the PV cells aren’t generating enough electricity during a normal day to replenish the store for the next night.  Indeed, in a worst case scenario, the PV cells might not even provide enough power to cover the normal needs during the day.

You can of course control this to a certain extent by increasing the capacity of your bank of solar cells.  If you need 20 kWhrs of electricity a day – 10 kWhr for daytime use and 10 kWhr to store for the night, then you’re less likely to run into shortage with a setup that is rated to provide 40 kWhr per typical day than with a setup that is rated to provide only 20 kWhr per typical day.

So the greater your surplus during a typical day, the less an amount of reserve storage you need.  If even a cloudy day sees your PV installation providing enough power for the day and the night, all you would seem to need is a single night’s worth of power to be stored.

We’d still like to increase that capacity to allow for mishaps and emergencies.  What happens if something fails in the solar setup and it takes you a day or more to repair/replace it?  Also, if you only need to recharge your batteries every other day rather than every day, clearly you’ll get twice the life from them, and if you are normally only discharging your batteries down to 50% full, you’ll again get much longer life than if every night you are discharging them down to 20% full.

If you are only using wind power, the first thing we’d recommend would be to rush out and buy some solar cells!  Some days there might be no wind, but some sun (and vice versa); by spreading your electricity generation between two different sources, you are reducing your risks and increasing your resilience.

Beyond that, it becomes harder to predict how much wind power you can expect.  You need to look at detailed wind logs for your location, and approximating the above ground height your turbine will be situated at, so as to get a feeling for average, best case and worst case daily and nightly power generation.

Using a process a bit like that we recommend for working out your water needs, you can proceed to calculate some likely pessimistic scenarios about the amount of wind power you might get, and from that, you can then work out how much stored electricity you’ll need.  Don’t forget to allow for an unexpected several day outage occurring at exactly the worst possible moment, too!

But, wait – before you do these sums, you should first re-examine the question of how much electricity you will need and use, and reduce this amount as much as possible.  The next three sections cover this concept.

Continued in Part Four

Please now click on to read the final part of this series, ‘Strategies to Reduce Your Need to Store Electricity‘.  If you’ve not yet read them, you might also want to read the first two parts of the series too – Storing Electricity and Using Batteries to Store Electricity.

We also have other articles on the general topic of Energy.

Jun 042013
Using solar water heating brings two benefits - greater efficiency and an easy way to store energy as hot water for later use when the sun goes down.

Using solar water heating brings two benefits – greater efficiency and an easy way to store energy as hot water for later use when the sun goes down.

This is the final part of a four-part article series about how to store electricity (better thought of as storing energy rather than electricity per se).  If you arrived directly here from a link or search engine, you might wish to start from the first part of the series here, then read on sequentially through the balance of the series.

A Different Sort of Energy Storage – Time-shifting Electricity Demand

Storing electricity is usually both the clumsiest and costliest way of productively using up spare/surplus electricity.  You lose some electricity when you convert it to however it is stored, you lose more during the storage process, and then you lose even more when you convert it back to electricity again.

So it is better to time-shift as much as possible to times when you have spare electricity.  One example of a time-shiftable process would be washing clothes and dishes (assuming you still will use an electric dishwasher in the future, which is unlikely).

With these types of activities, you can wait until a day with lots of electricity coming from the PV cells or wind turbine before washing your clothes (and/or dishes).

If you have an electric range, you should use it to cook food during times of peak electricity production.  Maybe you’ll change your eating habits and have your main meal of the day in the middle of the day (something many societies already do and which many health experts think to be a better approach to eating) so that the cooking energy is sourced when the sun is shining brightly or the wind blowing strongly.

If you are vacuuming, do that when there’s spare electricity, and never when you’re using stored electricity.  There’s almost never an emergency requiring urgent vacuuming in the middle of the night!

Try and match your own sleep and wake times to the sun.  If you’re sleeping during the morning with daylight flooding in to the retreat, but then staying up late at night, using electricity to power lights and possibly heating too, that is more wasteful than using the sun for light as much as possible, and sleeping in a warm bed during the coldest part of the night.

Take your shower/bath in the morning if possible so as to allow the system all day to reheat the water.  Or, alternatively, after using hot water at night, don’t use stored electricity to heat up the replacement water, and instead wait until the morning to do that.

Which leads to another strategy.

A Different Sort of Electricity Storage – Storing the Results of Using Electricity

Another approach to storing electricity is to store the results of using electricity.  We started to get into that in the preceding section – heat your hot water when you have spare electricity to do so, and then deplete it when you do not have spare electricity, and only reheat it again when you have the spare electricity back to do so.

An easy and low tech type of storage is to store heating or cooling energy.  There are special ‘storage’ heaters that will run when you have spare electricity and heat maybe a large vat of oil or even a block of concrete, then at night, you expose this heat source and allow the heat to transfer out and into the surrounding areas of your retreat.

You can also do this for cooling.  When there’s surplus electricity, make large blocks of ice.  Then, when you need extra cooling but no longer have extra electricity, allow the ice to melt, cooling the area around it.

These are low tech but sensible concepts.  Indeed, many large buildings currently use these types of systems for more efficient heating/cooling.  You can do the same.

Replacing Electricity With Other Energy Forms

Electricity is an ‘expensive’ form of energy – it is close to the top of the ‘energy pyramid’, just like beef is close to the top of the food pyramid (in terms of the amount of feed and water needed per pound of meat).

If you can replace electricity with other forms of energy – forms which may be more abundant, and/or lower tech and more sustainable into the indefinite future – you’ll be doing yourself a favor.

One example of this substitution is to mount a solar water heater on your roof.  That way, instead of using solar energy to create electricity and then the electricity to heat the water, you go directly from the solar energy to the hot water, in a much more productive/efficient process, and also in a lower-tech form.

A solar water heater is easy to construct and easy to maintain.  But as your PV cells fail, you’ll absolutely not be able to repair them yourself, and no-way can you fabricate your own additional solar cells in a low-tech future.

Another example is to use wood (or coal or peat) as a heat source for heating your retreat, your hot water, and possibly even for cooking with as well.

Or, if you’re using propane to power a generator, get a propane rather than electric stove and burn the propane in that stove.  You’ll use less propane to directly power your stove than to first convert it to electricity and then to second convert the electricity to heat on your stove.

How Much Extra Electricity Generation Capacity Do You Need

Remember that the first part of an electricity storage system is having ‘spare’ electricity to store!

Once you’ve done what you can to minimize your reliance on stored electricity, the next question becomes how you will get the electricity to store.

Clearly, you will do this by increasing the capacity of your renewable energy sources so they can simultaneously meet your normal electricity needs and also send extra capacity into the storage system you selected.

And, equally clearly, the electricity source(s) you have must be able to generate enough spare electricity each day to be stored to be used each night.

So you need to consider the answer to this question – ‘assuming a less than fully sunny day, or a day with poor rather than optimum wind, how much power do I need generated for the day’s requirements and to recharge for the night ahead as well?’.

Remember that most solar and wind generators are specified as having a certain capacity on a good/close to optimum day.  You’ll need to adjust the claimed daily capacity to more accurately reflect the real-world rather than best-case probability of electricity it will create for you.  Maybe you need to get a system which is apparently twice the capacity you need, just so that in periods of low generating conditions, it still generates enough for both your immediate and your storage needs too.

Now, for an interesting additional factor.  The greater your storage capacity, the smaller your surplus daily generating capacity needs to be.  This is because the extra storage capacity gives you a greater ability to average out the peaks and troughs of actual daily electricity production.

One more consideration.  Most lead-acid batteries require a certain minimum charge rate in order to effectively charge, so you need to be sure that your electricity source will deliver enough charge to actually load electricity into the battery.  Think of a helicopter – it uses a lot of energy just to hover – you don’t want your battery to just hover, you want its charge level to rise, so you need to provide more than this ‘hovering’ amount of energy to actually raise the battery’s charge.

Whatever you come up with, you must have a system that on an average/ordinary day will provide enough electricity during the day for all the daytime needs in your retreat, plus enough left over to replenish a typical night-time’s consumption of electricity, plus perhaps still more left over to replenish one more typical night-time’s consumption, too.

Electricity Will Never Be Cheaper Than Now

Spending $10,000 for a 5 kW solar array might seem like a lot of money, and of course, by any measure, it is indeed a substantial sum.

But – and you can absolutely trust us on this – in a Level 2 and particularly a Level 3 situation – your future lifestyle and ability to survive will be totally linked to your ability to generate your own energy, particularly in the form of electricity.

So get as much electricity generating capacity now as you can afford.  Particularly if it is modular, it can be either used or traded in the future, and you’ll quickly discover the essential nature of energy in a future Level 2/3 situation.

Read the Rest of the Series

If you’ve not yet read them, you might want to read the first three parts of this series too – Storing Electricity, Using Batteries to Store Electricity and Other Energy Storage Methods.

We also have other articles on the general topic of Energy.

Dec 262012
This four panel solar array measures 13.5' x 4.6', generates up to 920W of power, and costs $3500 (in Dec 2012).

This four panel solar array measures 13.5′ x 4.6′, generates up to 920W of power, and costs $3500 (in Dec 2012).

The ‘comfort’ level – some might say, the degree of advancement – of a civilization or life style can be closely approximated to its energy usage.

There’s a reason that we in the US are among the world’s largest consumers of energy, and it’s not that we’re wasteful.  It is because we enjoy a lifestyle that is generally better than most other nations around the world.  Just about anything and everything you do involves consuming energy.  Some of this energy consumption is obscured (for example, do you ever think of the energy consumed by shipping the 40 tons of goods we each require a year).  Some of it is assumed (for example, the energy that is required to make aluminum).  And much of the rest is taken for granted, even if energy used directly by you.

All of this ‘works’ for us because we are blessed with abundant and affordable energy supplies.

That will massively change in a Level 2 or 3 situation (see definitions here).

Life is both good and simple at present, and you seldom if ever consider the cost of the energy you enjoy.  And if you did want to, you could work out how much it costs to switch on a light, to run the television. to turn up the heating.

Well, perhaps better to say that in theory you can work out all these things.  Your utility supply company has a tariff, probably shown at least in part on every invoice you receive, showing the cost of each unit of power or gas you consume.  A bit of figuring and converting, and you can soon work out that, eg, if you’re paying 10c per kilowatt-hour (kWhr) for electricity, your computer is costing you 3.5c/hour to run, and the reading light in your bedroom is costing you less than a penny an hour, and so on.

These costs are generally so low that we don’t even think about them individually, although we might wince a bit when seeing our monthly or bi-monthly utility bill.

What will it cost us to do the same things if the grid goes down and if we have to live with only the energy we can make (or have stockpiled) ourselves?

The answer might surprise you.  Some things will be (sort of) free.  Other things will be so expensive that no amount of money will make them affordable (for example, an electric clothes drier).  Most of all, expressing costs in dollars and cents terms is no longer as relevant (because money, as an abstraction, will no longer be relevant).

Some Energy Might Be Almost Free

Let’s say you have some solar cells on your roof.  How much does that electricity cost you?  Sort of nothing.

Sure, it cost you a lot of money to buy and mount the array on your roof, and to buy a controller and run wiring and whatever else, but those costs are all now fully incurred.  So, in a sense, solar power is free, which leads to an obvious question and a necessary answer.

If Solar Power is Free, Why Don’t We All Have it Now?

The ‘variable cost’ of using the solar array you have installed for generating some power today might indeed be zero.  But while that cost today is zero, there was a substantial cost involved to install it in the first place, right?  You needed to buy the cells, install them, add electronic controllers, run wiring, patch them into your home power supply, and possibly set up a bank of batteries and regulators, too.

An accountant would also point out that sooner or later, the cells, wiring, controllers, and other related parts of the system will wear out, break, or in some other way fail and need to be repaired or replaced, so there are some future costs to be considered.

An accountant would depreciate or amortize the cost of the system over the total likely power generated during its life, and give you an average cost per unit of power as a result.

Furthermore, at present most of us enjoy amazingly inexpensive power from our utility companies.  The number of years it would take to pay for the up-front installation costs of a solar array can be substantial, and too long to make sense for many of us, in a situation where we are prepared to assume that we will continue to be guaranteed 24/7 access to unlimited affordable power, whenever we need it.

That is why everyone hasn’t rushed to buy solar arrays, yet.  But keep an eye on pricing – the payback time for solar arrays has been getting shorter and shorter, due to the massive reductions in the cost of the cells (thank you, China!) and the steady increase in regular utility-sourced electricity.  On the other hand, the US government has deemed that China has been ‘dumping’ solar cells into the US, and while you or I might be delighted at a chance to get bargain basement priced solar cells, and while you might think the greenies in the government would be delighted at China in effect subsidizing the US renewable energy movement by selling us product at below cost, that is, alas, not the case, and the government is looking at various trade sanctions to force China to sell them to us more expensively.

Anyway, back to the cost of solar.  These various accounting and costing issues are all correct, of course, but once you’ve installed and paid for a solar installation, then in terms of the actual incremental variable cost of using your solar cell array right now, the electricity flows with no extra money being spent by you, and with no need to ‘feed’ the solar cells with diesel or any other consumable.

About the only thing you’ll want to do is occasionally clean the cells, and even that is something you do at the same intervals, whether you’re using all the electricity generated by the cells or not.

So – from one perspective – this electricity is free.  Enjoy it while it lasts (which happily will probably be for 25+ years).

Some Energy Might Be Impossibly Expensive

Maybe you have an electric furnace, or an electric stove top.  Let’s say that one of these devices can take up to 10 kW of electricity when in use.  And let’s say that you can only produce 5 kW of electricity maximum from your generator set.

There’s nothing you can do.  No amount of money will get more electricity out of the generator.  You’re stuck.

Furthermore, how much does the energy created by your diesel generator cost?  There are two schools of thought on that, so please read on.

Some Energy Has a Very Different Historical and Replacement Cost

Talking about that generator – and let’s assume it is a diesel-powered generator – you know how much energy you get from the generator per gallon of diesel burned (we’ll say 10 kWhr per gallon which is a reasonably good rule of thumb to use).  You know that when you bought the diesel you are burning, it was costing you $4/gallon, so you know that each kWhr has an underlying cost of 40c.

But that is only correct if you can conveniently replace the diesel you are using, and at the same cost.  You are best advised to consider the cost of anything like this in terms of the replacement cost of the source fuel you are consuming, rather than in terms of the historical cost.

If there’s no more diesel to be had, then the cost of the diesel you do have has just gone up massively, hasn’t it.  What is the replacement cost of a gallon of irreplaceable diesel fuel?

You’ll need to start thinking of sourcing/creating bio-diesel for the future, or other completely different means of being able to generate electricity as and when needed, and you’ll need to consider what the costs will be and how sizeable the supply may be.

Note the phrase ‘as and when needed’.  That is the very significant difference between solar and wind power on the one hand, and a diesel generator on the other.  Solar and wind power only flows when the sun shines or the wind blows.  Much of our power needs would normally be later in the day and at night when it is cold and dark, and when we want to cook our evening meal, and this is a time when the winds typically calm down and of course, the solar cells stop entirely.

So a diesel generator and its diesel fuel can not be replaced by solar or wind power, unless there is some way of storing up the power so it can be used when it is needed rather than when it is generated.  The most common means of power storage – lead acid batteries – is clumsy and the batteries have finite lives, both in terms of years and also in terms of the number of charge/discharge cycles they can withstand.

The True Cost of Energy in the Future

Replacement cost is the true cost of energy in the future.  And when we talk about ‘cost’, we don’t mean dollars and cents.  We mean ‘How long will you have to work, what will you have to do, in order to create the energy you are about to consume?’.

We see a future where energy becomes the key measure of one’s ‘wealth’ and the means of measuring one’s energy value is the amount of time it takes to create the energy you have and use.  This will give you a meaningful way to appraise the appropriateness of any particular energy use.

For example, if running your electric dishwasher saves you 30 minutes of time, but if the work required to provide the power for the dishwasher requires two hours of your time, then who will want to use their dishwasher any more?  It just doesn’t make sense to work for two hours in order to save 30 minutes of time.

But if one hour of work provides you with light and video or audio entertainment for four hours, that is probably an acceptable ‘cost’ – assuming, of course, that you have a spare hour of time to allocate to creating that energy.

Which touches on the other part of this equation.  How much is your time worth and how much extra time do you have?  If you are locked in a desperate struggle for survival, all day every day, simply working your land to create food to subsist on, then you probably don’t have either the time to create the energy to power your home entertainment system or the spare time to then enjoy it in the evening.

Some things are harder to equivalate.  It is easy to say, in the dishwasher example, that it makes no sense to work for two hours to save 30 minutes, but what say you are instead considering ‘I have to work for two hours to increase the temperature inside by residence by 5 degrees for a day’?  Which is better?  More clothes and blankets and less work, or more work and more comfortable home temperatures?  Of course, that depends – if the ambient temperature is 40 degrees, you’d probably work to bring the temperature up, but if the temperature is already 65 or 70 degrees, maybe it becomes less important and other things take higher priority.

Nonetheless, a key measure of energy will become the number of man-hours it takes to create a given amount of energy.

Energy Opportunity Costs

So we’ve just said the key measure of energy ‘costs’ in the future is the number of man-hours it takes to create a given amount of energy.  Yes, that is true, but there is more to it than that.

Another issue is the ‘opportunity cost’ of any particular energy use.  By ‘opportunity cost’ we mean that you will typically find yourself in an ‘either/or’ situation – either you use some energy for one thing or for another thing; whereas at present we seldom have to choose, and can happily choose ‘both’ as our preferred option, that will not be the case in the future.

So you might find yourself with ‘low cost’ energy (eg solar) but with insufficient of it to power everything you want.  You then have to decide on an either/or basis – either I can use it for this or for that – and the value/benefit of the thing that you don’t use it for represents the ‘opportunity cost’ of the energy.

Only when you can have every electrical appliance switched on at the same time does the opportunity cost dwindle down to zero.

At any given time, your energy cost needs to be considered as a measure of the most expensive energy source you are using for the final ultimate kWhrs of energy you are consuming.  Sure, some of the total energy being consumed might be ‘free’ solar, but the fact clearly is that if you reduce (or increase) your energy consumption, the thing that changes first is your use of your least desirable/most expensive energy.

Energy Covers More than Just Electricity

You need to consider your energy needs – and the solutions/sources for them – not just narrowly in terms of electricity.

While electricity – if in abundance and appropriately priced – has the benefit of being able to provide energy for almost any and all requirements, in a Level 2 or 3 situation, the chances are that you will almost certainly not has as much electricity as you would like, and the cost of at least some of the electricity you use, at some times of day, will be very high indeed.

Furthermore, by diversifying your energy sources, you reduce your dependency on a single source.

Some examples of non-electrical energy sources and applications would include solar heating for your hot water, a wood stove for interior heating (and possibly also to heat water too), or a piped hot water system for heating powered by a wood burning boiler.  A gas-powered cooking range is another example, as is a wind powered water pump, maybe even a water powered mill if you’re fortunate to be close to a river.  A horse-drawn cart is an alternative to a gas or diesel-powered wagon.  Hanging washing out to dry on a clothesline rather than using an electric tumble drier.

Your best energy sources will depend on where you live and what is available to you, and may vary depending on the season.

Some Energy Will Cost More at Some Times than Others

The law of supply and demand will of course apply much more strongly than it does at present, and particularly because it is very difficult to conveniently store energy at times when it is being generated in quantities greater than needed at the same time.  Lead-acid batteries of some type or another are the best choice for many people when it comes to storing surplus energy, but they have a very finite life and when that has expired, you will find it difficult to replace the batteries with new batteries.

A more promising technology is a flywheel with magnetic bearings.  This can store energy with little loss for 4 – 8 hours or even more – enough to tide you over an evening until the next day and the resumption of solar power generation.

However, as an interesting aside and an insight into the considerations you’ll have to think through when you become, in effect, your own electricity utility, although most of us pay the same amount for every kWhr of energy we consume, the underlying cost to the utility company can vary enormously depending on the time of day we are consuming it.

For example, a utility might have some of its power sourced from hydro-electric power, some from gas/oil/coal fired power stations, and some from nuclear power.  In addition, it has an agreement with other utilities to sell its excess capacity to them, and a matching agreement to buy excess capacity from the other utilities if/when needed.

Maybe the utility’s cheapest electricity is from its hydro stations, then its next cheapest from its gas-powered stations, then from nuclear, then from oil/coal, and its most expensive electricity is when it has to buy it in from other utilities.

At some times of day, the utility might be able to provide all the power needed by its consumers via its hydro generating capabilities.  But at higher demand periods, it has to ramp up its other power generating capabilities, and at peak demand, it might have to buy in more power, possibly at a cost of as much as ten times greater than its hydro-power.

A similar situation will apply to you in your retreat.

During the day, with the sun shining strongly on your photo-voltaic cells, you might be able to meet all your energy needs from the solar array(s) you have.  This is sort of ‘free’ energy, other than perhaps having an opportunity cost because maybe there is insufficient surplus to concurrently recharge up your lead-acid battery bank – power that you’ll need overnight when the sun has set.

If you have wind power, that too will rise and fall in terms of the amount available to you, and at times may be abundant, while at other times may be inadequate.

In an evening, you might have multiple sources of energy.  You might have a wood burning stove to provide warmth in your dwelling and perhaps to also heat up your hot water supply.  You might have a propane powered stove to cook on.  Electrical appliances might be powered by a bank of lead-acid batteries, and/or possibly by a diesel generator.

Your hot water might be solar heated, but if you use too much of it, you’ll either end up with cold water or need to use an additional energy source to heat the water until the solar heat returns the next day.

You might think that the wood for the stove is free, but just because you’ve not handed over cash to someone in exchange for the wood does not mean it is free.  You’ve had to first grow the tree, then you’ve had to fell it, cut up the logs into fireplace sized chunks, and transport it from where the tree grew to where your residence is.  All of that consumes a lot of your time and effort.

Adapting Your Lifestyle to Your Energy Sources

Many years ago, rural dwellers kept much simpler lives and schedules.  For example, they would tend to get up when the sun rose, and go to bed after the sun set.  This concept has been partially applied to the notion of daylight saving time which possibly saves a small amount of energy each daylight saving season, as well as probably enhancing our lives by matching our waking hours more closely to the daylight hours.

You need to adopt similar strategies in a Level 3 situation, and probably also in an extended Level 2 situation.  There are other things you can do as well.  For example, use electricity for tasks when it is most abundant – if you are fortunate to be able to power an electric washing machine, only run it when the sun is brightly shining (or the wind blowing) and you have an abundant inflow of electricity.

If you have solar heated hot water, plan your main hot water draws at times when the water is most likely to be sufficiently hot to use, and ideally when there is still a chance for the replacement water to be heated some, too.  In other words, take showers and baths in the afternoon rather than in the morning or at night (oh, and one of the first things to go will be our current ‘indulgence’ of showering/bathing every day and sometimes even more than once a day!).

Time your energy needs for cooking to an appropriate time of day that aligns with your energy source availability and chance your meal schedule to match.  If this means you have your main meal at lunchtime rather than dinner, so be it.  Many people do so already, and indeed, it is generally considered healthier to do so.  Some medical experts say that we should eat our food in a direct inversion of the way people often eat at present.  Instead of a small breakfast, medium lunch and large dinner, we should have a large breakfast, medium lunch and small dinner.

And, of course, set your sleep patterns so that you’re not ‘wasting’ daylight hours asleep at one time of day and then needing to use energy to create light at a different time of day.  Although lights are one of the smaller energy consumers, they are generally needed at a time of day when energy is most expensive (ie no solar) and so it is important to minimize your light requirements.

The Ideal Energy Source

If we were in a perfect world, we’d choose hydro-electric power as our energy source.  Why?  Because it is a 24 hour a day source of reliable power, limited only by the daily water flow and any seasonal reductions in water volumes.

But hydro-power requires lots of water and a sizeable drop in water levels to work.  As a rule of thumb, to calculate the power generation capabilities of a hydro station, ,multiply the water head in feet by the water flow in gallons/minute, and divide the answer by 10 to get the number of watts being generated.  In other words, with a 10′ head, you get one kWhr of electricity from every 60,000 gallons of water.  A greater water drop (ie head) would reduce the water volume required, and as a practical matter, if you have much less than 10 ft you start to have too little water pressure to effectively harness (about 8′ is currently considered the minimum).

Even if you have a possible water source on your property, EPA and other restrictions (both federal, state and possibly even county level too) may restrict your ability to take over any streams/rivers on your property, and therefore will constrain your ability to construct a dam and micro/mini hydro generating facility.  You’d need to carefully check this out, but if you have water rights to the stream, that is a good first step that may lead to approval.

Hydro electric power is characterized by high capital costs to create possibly a dam and the generating facility, but once it is in place, it then has of course no ongoing costs and is relatively undemanding in maintenance requirements.  A close to ideal source for after TEOTWAWKI – and, of course, noting the essential need to diversify risk in everything you do, you’d want to back it up with solar and other energy sources as well, ‘just in case’.

There are types of ‘in river’ turbine generators that you can simply drop in a river and use to extract some of the energy from the water that flows past, but these are very low powered units.  On the other hand, they might provide a useful source of power for night-times when your main solar sources become inactive.

Planning Ahead

When you design and build a retreat, you need to plan its design based not on the current energy abundant situation we enjoy today, but on an adverse situation in which we need to move to our retreat and become self-sufficient.

This means that a major focus on your retreat construction has to be energy efficiency.  Construction techniques that make no sense when energy costs only 10c/kWhr become much more appropriate when energy costs spiral to a future equivalent of, say, $1 or $2/kWhr, or the even uglier reality whereby you’ll be ‘energy poor’ and have insufficient energy for your basic needs, no matter what the cost.

Before you even start to design and construct your retreat, you need to apply these considerations to where your retreat will be located.  In a hot climate, you might prefer a sheltered area that doesn’t get so much sun, but in a cold climate, you might need an area with great southerly exposure.

Clearly the dwelling will need to be super-insulated, and built around its incorporated heat (and possibly cooling too) sources, rather than having them added on almost as an after-thought and as a low priority.  You might have to compromise some eye-appeal for functional survivability and energy efficiency.

For example, don’t run heating/cooling ducts through the basement areas or crawl spaces – run them through the living areas of the house.  You probably don’t need to heat or cool the basement and crawl spaces, but by keeping all the ducting inside your house’s living areas, there is no ‘wasted’ heating/cooling.

One happy coincidence – walls with enhanced insulating properties tend to be stronger walls in general, better resistant to hostile attack and adverse weather.

Here’s one resource to get you started on considering such things.  Here’s another, but it aims to merely enhance your home’s energy efficiency by 15% over a 2004 published standard – that’s massively underachieving in terms of what your objectives should be.


The biggest change in our lives, come a Level 2 or 3 situation, will be our transitioning from our current ‘energy rich’ lives to a future ‘energy poor’ existence.

At present, we happily never really need to consider about reducing our energy consumption, other than being motivated by a (probably misplaced and altruistic) desire to ‘save the planet’ by cutting down on our energy use, and energy is so cheap that most advanced energy-saving strategies fail to be cost-justified.

This will massively change when we have to create our own energy rather than have it appear, as if by magic, out of the sockets in the wall.

We need to plan and prepare for an energy-scarce future, and to take steps to reduce our dependence on energy so that we can still live comfortable lives, with massively reduced ‘energy footprints’.  We need to build our retreats based not on present energy costs, but on the future costs (and availability) of energy after TEOTWAWKI.

Solar is becoming affordable and effective, but only when the sun shines, and probably not for all of the energy-consuming devices in a typical house (unless you have a large budget and are in a very sunny location).  Additional energy availability for evening and winter times will be the biggest challenge for most people.

May 102012

Fuel storage systems vary enormously in capacity, cost,  and sophistication

Some preppers have truly impressive fuel dumps, with literally thousands of gallons of gasoline stored at their retreat, representing a multi-year supply, assuming they are using it regularly.

Ooops – that may be an incorrect assumption to make.  If they’re not living in their retreat full-time, their stored fuel is probably just sitting there from one month and year to the next.

What’s more, if they do occasionally take some fuel out for general consumption, and then subsequently top up their tanks again, what has just happened?  It is like the jug of ‘fresh milk’ in the fridge.

Understanding this issue is an important part of developing an appropriate storage plan for your fuel supplies.

The Always Fresh Jug of Milk (or Pot of Coffee) That Goes Stale

Each morning, a housemaid would take out of the fridge and top up the decorative jug of milk and put it on the breakfast table for the family to pour over their cornflakes, into their coffee, and so on.

After breakfast, the maid would return it to the fridge, and top it up again from the carton of milk bought at the supermarket.

But over time, the milk became staler and staler, because each time it was topped up, a little fresh milk was added to a lot of older milk, so that some of the old milk stayed and stayed and stayed.

You might notice a similar thing in a restaurant – the carafe of coffee gets half emptied, and then the hostess tops it up with a partial fresh carafe of coffee.  The next person who gets a cup gets half a cup of fresh and half a cup of stale coffee.  Then, after half the carafe has been emptied again, and it is topped up with fresh coffee again, the next cup has a quarter mix of double stale coffee, a quarter mix of stale coffee, and a half mix of fresh.  And so on and so on, with the average age of the coffee, milk, or whatever, getting older and older each time it has been topped up.

To avoid this, you need to fully empty the container before refilling it.

What Type of Fuels to Store

Perhaps the ‘big three’ liquid fuels that most people consider storing would be gas (petrol), diesel, and propane (lpg).  Note that we are confining this discussion to liquid fuels – please also see our separate detailed article on coal as another possible energy source for your retreat.

Both gas and diesel have storage life challenges, whereas propane is relatively straightforward to store for extended periods of time with little concern about it deteriorating in quality.

You’ll need liquid fuel for some obvious purposes.  The two biggest requirements will probably be power generation and transportation; you may also use liquid fuel for smaller equipment motors, for heating and for cooking.

Ideally it would be great if you could settle on only one form of liquid fuel for all uses.  Certainly generators can be powered by any of these three fuels, and it is possible to get motor vehicles that run on propane or which are dual fuel, running on either gas or propane.

In terms of storage costs, diesel is slightly the lowest (because each gallon of diesel fuel contains more energy than petrol or propane) and propane is the highest (you need special pressurized tanks and propane has the lowest energy content per gallon).

In terms of cost per unit of energy, this varies depending on how much tax you have to pay on the different fuels, and it would be appropriate to research the costs for all three fuels that you would buy for non road transport purposes (and for road transport purposes too of course).  Some states nowadays include all the ‘road/transportation’ taxes in the cost of gas or diesel, even if it is being used for eg farm equipment, boats, or generators.  Others are not quite so unfair in their approach.

The relative price between petrol and diesel doesn’t change a great deal over time, but the relative cost between propane (which is often made from natural gas) and petrol/diesel (which of course comes from oil rather than natural gas) can vary widely.  At present propane seems to have the lowest cost of the three fuels, with diesel perhaps the middle cost item and gas as the highest cost.

In Washington state, at the time of writing, bulk gasoline is about $3.90/gallon for regular, bulk diesel is about $4.10, and bulk propane is about $2.30.

But it is not very meaningful to simply compare the respective costs per gallon of fuel, because each gallon of fuel delivers a different amount of energy, measured in BTU/gal, or if you prefer, in MJ either per liter or kilogram.

To match these per gallon costs to costs per BTU of energy, gasoline is about 3.12c per 1,000 BTU, diesel is 3.00c (and you’ll get better efficiency – ie more power – from each BTU as well) and propane is 2.52c; clearly the cheapest of the three fuels in terms of ongoing costs of propane.

Diesel motors are typically more expensive than petrol motors, but they are also typically massively more reliable and much better for extended operation (such as with a generator) and also can usually be modified to accept bio-diesel type products of various sorts, making them more flexible for the long-term where your bunkered stores of fuel are diminishing with no replacement in sight.

On the other hand, just about everything from hedge trimmers to chainsaws to cars, trucks, boats and planes can be found with gasoline powered motors.

And while it is hard to envision a situation where you’d feel you had spare fuel you didn’t need, if you wanted to trade fuel for something else with someone else, they are probably most likely to need gasoline first, diesel second, and propane third.

Relative Perishability of Liquid Fuels

Petrol and diesel are perishable.  Both fuels can have a problem with moisture – particularly petrol with alcohol added to it; the complex mixture of chemicals that makes up petrol (petrol is not just one pure liquid, it is a veritable soup of different chemicals) can decompose and change properties, and these days there are bacteria, algae and fungi that enjoy living in and eating diesel.

Here’s an excellent article with a fascinating graph that gives a good overview of the complexity of what is blended into gasoline, and some of the issues associated with modern fuels and the engines that run them.

The bottom line – you can risk harming your engine with older diesel or petrol, and or the engine might simply fail to run at all.  Generally both petrol and diesel starts to become appreciably affected by aging within about 3 – 6 months (or less) of being purchased.

Apart from doing the same things with fuel as you do with food (ie keeping it in a cool dry dark place) you’d want to provide a good seal on the tanks (to stop moisture and oxygen coming in and volatile compounds going out) and should treat the fuel with PRI-G (for petrol) or PRI-D (for diesel) once every year.  Diesel might also require some PRI-SOLV and/or PRI-OCIDE too.

PRI-G and PRI-D need to be applied to fuel annually, although some tests have suggested that a single dose of PRI will have positive effects spanning more than a year.  One gallon of PRI-G/D will treat 2,000 gallons of fuel, at a cost of 4 – 6 cents/gallon/year.  If you buy in bulk drums rather than 1 gallon containers, the price can drop further.

With such a low cost per gallon, and with the desire to have as good quality as possible fuel, you should add PRI each year, at least until such time as you run out of PRI itself.

It is unclear how many years of life you can get by adding the PRI to the fuel each year, but it seems at least ten years, and perhaps more like 15.

There’s another issue to consider as well when planning for an extended period of living on one’s own.  How long does the PRI product itself last?  The manufacturer says that it has a shelf life, in unopened containers, of three years, and recommends it be stored out of sunlight and in a cool place.  We endorse that recommendation, of course, and suggest you keep it somewhere as cool and dark as possible, and plan for perhaps no more than a five-year effective life.

So, in total, it seems you can probably manage to store diesel and petrol for at least six years before needing access to a freshly made supply of PRI.

There is a better known product also for sale, STA-BIL.  It is more expensive and based on their claims, seems to be not as effective (in terms of long life extension) as PRI.

The PRI products also claim to be able to rejuvenate and restore old fuel that hasn’t been treated with PRI previously.  STA-BIL says their product can’t do this.

A fuel ‘polishing’ system – at the very least, some fine filters, and perhaps even a centrifugal system – would also be recommended, particular for diesel, so as to ensure the fuel when you use it is as clean as possible and least likely to block the injectors in a diesel engine.  ‘You are what you eat/drink’ applies not just to the need for us to consume healthy food ourselves, but to our mechanical equipment too.

Propane on the other hand is relatively inert and can last for an uncertain amount of time, but probably some number of decades.

The problem with extended storage of propane will relate more to the integrity of the tank it is stored in and the seals where fittings connect to the tank and each other.  The propane is under pressure in the tank – several hundred pounds per square inch, so even the slightest bit of a leak along a weld seam or seal will see propane slowly escape over the time it is stored.

Your Fuel Dump Needs to Have Multiple Tanks

Remember our comments above about the jug of ‘fresh’ milk or coffee?  If you are going to have a fuel dump at your retreat, you need to have at least two and ideally four or five or more tanks.  You should empty each tank fully, in sequence, and only refill tanks when they are completely empty.

That way the amount of stale fuel carried over from one refueling cycle to the next is minimized, and by having four or five tanks instead of only one or two, you will in theory only have one of your four or five tanks empty at any time, meaning your total fuel supply never drops much below about 80% full.  With only two tanks, you’d not trigger a refill event until after you’d used up half your total supply, a much less positive situation.

Note that this is less a requirement for propane, due to it not appreciably aging.  It is more acceptable to simply top up your propane tanks, mixing new propane in with the old.

Storage Tanks

Some companies will rent you storage tanks if you contract to buy your fuel needs from them.  The rental cost can be anywhere from $1 a year up to much more than that, depending on both the size of the tank and your projected fuel purchases.

While it seems appealing to get a subsidized tank as part of a supply deal, remember that favorite aphorism – TANSTAAFL – and realize that a subsidized tank is actually being subsidized not by your supplier, but by you.  You just don’t necessarily realize this is what is happening, the way the numbers are presented to you, but for sure, the underlying costs of the ‘free’ storage tank are being paid for by you.

You’re also locked into only one supplier.  And you’re more or less stuck with the size tank they agree to lease to you – and for sure this will be much too small a size if you’re wanting to be able to store several years worth of projected supply.

There’s another thing about leasing storage tanks from someone else.  When LAWKI ends, what is to stop the supplier from turning up on your doorstep and saying ‘sorry, we want our tank back, here’s your $1 returned to you’.  They could quite credibly claim that ‘force majeure’ allowed them to terminate their contract.  Sure, they’ll give you a day or two to transfer the fuel which you own out of their tank and to some other storage facility (or probably would agree to buy it back from you at whatever price you earlier paid for it), but where or how are you going to transfer propane?  How many 20lb barbeque sized tanks would it take to hold 1,000 gallons of propane?  (Answer = 210 tanks).

You probably wouldn’t have thousands of gallons of storage facility for gas or diesel either, but the loss of your propane tank would sure be a worst case scenario.

So our suggestion is that you should buy your own tanks for storage.  If you’re storing petrol or diesel, we suggest you use underground tanks – they are discreet, they are temperature controlled and kept cool year round (by the earth around them), and they are protected from many types of physical risk or threat or abuse.

Propane Storage Options

Propane is trickier to store than petrol or diesel, due to it being kept under pressure when in liquid form.

Although it is possible to have underground propane tanks, they are more prone to problems, in particular because they flex and move as between when they are nearly full and nearly empty.  It is possible to create satisfactory underground storage for propane, but the risk of problems is higher, and in a post TEOTWAWKI situation, you can’t simply telephone the local propane tank servicing company and have them repair/replace a tank and refill it with replacement propane if you discover your tank has sprung a leak and emptied out.

On the other hand, an above ground tank is more vulnerable to physical attack/accident and is a more obvious visual clue that you probably have some valuable and tempting fuel on your property.  If fire and building codes permit, it might be appropriate to consider erecting a shell building around your tanks to at least obscure them from prying eyes.

A 1000 gallon above ground propane tank costs $2200 – $2500, and installation is likely to be that much again, so there’s a major cost associated with a propane store.  In other words, you’re looking at an all up price of about $5/gallon for a large-sized propane storage facility.

As an alternative, you could buy a huge propane trailer to be truck hauled.  These could have capacities of 10,000 – 25,000 gallons, and would cost you, ex-China, $30,000 – $50,000 plus shipping.  This would reduce your overall cost per gallon for storage, and you could probably buy propane at even lower costs, but your up-front investment would be larger (this is an understatement) and you’d have additional licensing requirements.

There are smaller sized tanks too – 500 and 250 gallon tanks, and even smaller ones than that, but as the tank size goes down, the cost per gallon of storage capacity starts to increase.  The sweet spot for most people will be in the form of multiple 500 or 1000 gallon tanks.

No matter what the fuel, we’d prefer to have two half sized tanks rather than one full sized tank.  That way if something should happen to a tank, you’re not risking your entire fuel supply.

Tank Maintenance

Diesel and petrol tanks need occasional maintenance – primarily to do with draining any water that may have accumulated on the bottom of the tanks, and repairing any rusting the water may have caused.

In ground tanks probably have sacrificial anodes attached, so these anodes rust away rather than the tanks.  The anodes need to be replaced from time to time.

All tanks (including propane) need to have seals checked.

For these reasons it is good to have a multiple tank storage system, allowing you to take one tank offline for maintenance and repair without compromising the amount of fuel you keep in store.

Lubricant Too

Would we be stating the obvious by mentioning the need to also keep lubricants for whatever engines will be burning the fuels you are storing?

Keeping oil clean and fresh is even more important when engine failures are not just costly and inconvenient, but may become life threatening and mean the difference between power and/or transportation and not.

Fortunately you probably won’t need thousands of gallons of lubricants.


Adopting the best practices detailed in this article, you can realistically expect to be able to store petrol or diesel for at least five years, and propane for pretty much as long as you choose to.

Propane is the best value fuel, but it has the highest up-front costs of buying the storage tanks you’ll need.  Diesel is probably best for generators.  Petrol (gasoline) the usually the most expensive fuel, and harder on engines than propane, but is also the fuel you are most likely to be able to use with the most number of engines.

For ongoing use and general ‘normal’ living, we’d recommend propane, storing enough for a year or so of normal consumption – whatever represents a sweet spot as between cost of the storage units and cost per refill and the quantity discounts you might be able to secure.

For medium/long-term disaster preparedness, and to power vehicles of various sorts, you might want to have bulk supplies of diesel and/or petrol to augment the propane you keep on hand.