I am a big believer in solar use, have 33 panels on my home, saves me over 3/4's of a billing every month, I am getting a full size solar battery and a medium extra block as well, installed middle of February, had the panels installed on my home 8 years ago and then I waited for the price to stabilize on the battery ! I have 3 freezers for fur and one for family use as well as three fridges, as well as when I'm doing welding jobs for side work. Run house light as well, we do watch to make sure not leaving any left on when not in that room, we do our holiday lighting as well from Halloween till end of January as well, use all the right power saving lights as well, it all adds up when you watch how you use them, not afraid to use the electric ovens either have outside light as well on patios. So we don't skip out not having stuff, we just use it watchfully.
I am now working on a solar powered squeaker unit that will run all year long, day or night, will be a tremendous savings for customers on old battery use over the life of regular battery's !!
Can't help you with the figures and number crunching though I left that up to the sellers and installers, my state electric company has a big push on the home battery's now and is giving out large amounts of extra cash for the cost of them for enticement to have them put in as well, the company doing it is giving a bonus gift as well, either use how you like or on the cost, which I did.
There are a couple of government incentives to take as well, depending how large a battery you are receiving. We qualified for that as well
Now for the ugly, part, even though the panels I got for my home I waited for, still were expensive, but I did get German made panels instead of the China ones, better panels and life, I could have slipped by with only 16 panels as thats the average use here, but went for 33 self efficiency down the road, which pushed the cost up pretty well, I also received a nice deposit gift for doing so, but still cost more than most people would spend, at least around here, the home battery I watch go up and down for all size's of them and finally decided this year it was with in my reach to get and use with all the discounts and incentives given to get one, brought the price way down, with so many of them to use.
If you only want to help your billing it takes some time to do if you don't pay the price out on them, if you want a battery and be off grid like I am going to be, it will cost more than most people feel the need to, but at the rate the price of electric service is its a 10 year difference in savings for us to go with the battery .
Bottom line way to high still for most people unless able to pay right off to start, smaller stuff like my squeaker power will be way cheaper in the long run and I can buy in bulk for the use on the unit cheaper than others can when not having a business to get such a discount. Probably be coming out with that unit next trapping season. Will be selling the unit with the panel attached and a battery as well !!
Sorry for the long read, and not answering your math problems, never was to good at them any way, but I do know saving when and if one can afford to take it, and solar is not probably going to come down much any longer with so many more makes of the panels and battery's now !!