Detailed Instructions for the Daily Tab
The good news for the Daily Tab is there is nothing to input on this page. The page uses the information you entered on the Constants page to calculate the values it displays for you here.
There is a lot of information on this page (2,560 calculated values in total!) and you don’t need to look at them all. But there are a few things that you should focus in on so as to get a feeling for how your system would work.
This shows you information for every day of the year. We start off not on 1 January, but instead on 1 April, which we are arbitrarily considering to be the start of your ‘energy year’. We do this to make the model simpler, and in the expectation that by 1 April, your solar power system will be giving you a surplus of power every day to start saving up for the winter months.
Indeed, there’s the first thing to look for in the results. Are you indeed getting some net power stored each day during March? If you are not, then your system is almost surely way too underpowered, and you should consider adding some more panels to it.
The key column is probably the ‘Total Power Stored’ column. This shows you the daily amount of power you have in your reserve power storage. You want to see this number gradually make its way up to its maximum capacity at some point, and hopefully stay up there until perhaps November before starting to go down again.
A happy column is the ‘Net Unstored Surplus Power’ column. This is spare power you have after you’ve used whatever you need for the day and then used any more available to top up your energy storage facility. When the energy storage is full, you might then have more left over – if you do, it appears here.
These are the days when you can treat yourself to plenty more electricity, because there’s nothing else you can do with it.
A not so happy column is the Net Power Generated/Consumed column. This shows you, each day, if you are generating more or less energy than the amount you are consuming.
Don’t panic if you are in a net consuming power situation for a while. That’s why you have an energy store. But in the months when you are in this negative situation, you know you need to be more sensitive to your energy usage so as not to run out, and so as also not to need to spend huge amounts of money expanding your energy store.
Now, as you’ve been looking through this page, you’ve probably noticed something. Although there is information for every day of the year, most of each day’s information is the same for each entire month. We both know that’s not what will happen in real life. Some days you’ll get more power, and some days you’ll get less, right?
However, in a typical month where you are generating more power than you are using, and/or when you have plenty of spare stored power for ‘just in case’ scenarios, that doesn’t really matter.
It does matter though in your ‘worst month’ – the time when you go down to zero power in your storage, and when you’re also not generating enough power each day to meet your daily needs.
The first comment about this tough time of year is that ideally you’ll never get down to zero. If you do, then your system is underpowered and you should think about adding either more panels or more storage (or more of both!).
So maybe your worst month sees your stored power go down to its annual minimum, but not quite to zero. Whatever that month is, perhaps we need to take a very careful look at what is happening each day during that month. If you are at almost zero, it only takes a very small amount of bad weather/bad luck to reach zero and to start suffering the consequences.
We suggest the first thing to do is to invest in an adequate system so as to avoid any months reaching zero, and hopefully so you don’t even get close to zero. If you manage to keep, even on the day with lowest reserves, several day’s worth of power in your stored energy system, then you can probably relax.
But if you want to now look over your most difficult month with a careful microscope, please move on to the third tab – the Critical Month’ tab.
You’ll also notice that the values suddenly jump from the end of one month and to the start of the next month. That is of course unrealistic – in the real world, sunlight values will always be either gradually trending up or down, depending on the season. We’ll adjust that in a future version of the model, but for now, the impacts of these sudden monthly changes aren’t very meaningful in terms of the validity of the model data itself.
For more information, please return to the main page explaining the Solar Energy Calculator spreadsheet or click on to go to the page explaining the Critical Month tab.