Earlier this summer, in late June, I came back from a heat wave in Europe (96F in Paris) to 122F at home! That month of June, my home electricity usage was 120 kWh/day in the hottest days, and we were not even home.
So, watching solar panel prices at $0.50/W, I thought it was time for me to do a DIY solar project. I will not apply for any subsidy, and my system will be an off-grid one, and not grid-tied. The idea is that it will run one or two supplemental mini-splits (to be installed), to off-load the central 5-ton AC.
Then, seeing that the on-peak rate lasts until 8PM while the outside temperature can be above 100F until midnight, it would be nice if I could store some of the surplus energy, if I will have any, to continue supporting the AC after sundown. Hence, the battery bank.
The 17-kWh capacity is a drop in the bucket compared to the 120kWh daily usage, but it's a start.
Elon is offering a Tesla Powerwall with a 13.5 kWh battery for $6,200, and the additional installation cost was reported to be from $5000 to $8000.
I will not be able to design one as slick, but I will be able to beat that price, and still have money left over to build a pergola to mount the solar panels on top, and also to have a couple of mini-split AC's added to the home. It's the big advantage of DIY for no installation costs.
A lot of work, but also a lot of fun. I have learned a lot about the quirks of lithium battery, specifically the Lithium Iron Phosphate type.
I also already have 3 kWh in a bank of 3 batteries for my motorhome. Still working on how to install them with a DIY BMS (battery management system).