Can you mention how much did you pay for whole installation, panels, battery and electrics?
Very good question, and it's a long story because it involves a lot of moving parts. I'll try to give you the "condensed" version.
2012 - installed 5 kW of PV built on a solar shade structure for our patio. I think the cost was about $50K for the whole thing including engineering the building the shade structure. The entire cost qualified for the 30% Investment Tax Credit and about $2K in California state incentives.
Around 2017 I was fortunate to enroll in a California Energy Commission sponsored "smart home study" where they installed a L2 charger and 8 kWh Sonnen storage battery, which I got to keep at the end of the study in 2019. I just had to agree that they could remotely control the L2 charger and the battery's charge and discharge cycles and have access to my data for two years. I was driving a Ford Fusion energi plug-in hybrid at the time, and I didn't need a panel upgrade because I already had a 200 amp service. We don't have any natural gas service so our home was mostly electric except for water heater, furnace and clothes dryer, which were all propane.
2019 - the study ended and I got to keep the charger and the battery. One reason we wanted the battery was for emergency backup, but found at this point that it was a stripped down version without a transfer switch. I found a local Sonnen dealer who would give me $5,000 credit for the four 2 kWh battery modules toward purchase and installation of the full functional 10 kWh battery. This involved moving most of the house circuits from the main panel to a new "protected loads" panel next to the battery. These would be the circuits that would still operate when the grid goes down (we live in an area in Southern California that's subject to "Public Safety Power Shutdowns" during dangerous fire weather). I think the total cost (after the "trade-in") was about $12,000. This also qualified for the 30% Investment Tax Credit.
It was around this time, after taking an interest in the battery operation and looking at my own data, that I realized that this could present a good opportunity to switch from our fixed rate plan at SDG&E to the TOU tariff. We also had become more intentional about electrifying our home. Between 2017 and 2021 we purchased a heat pump clothes dryer, removed the propane furnace and replaced it with a high efficiency zoned air-to-air heat pump system, and replaced our water heater with a heat pump hybrid unit. I'm not going to go into the total cost for all of these because it required some major modification of ductwork and some other things, but they definitely played into the final payback, because propane costs here about 4X as much as natural gas per kBtu, and the heat pump units are about 4X the efficiency of the propane (or NG) units. Plus we were able to completely get rid of the 300 gallon potential propane bomb sitting next to our garage. In 2019 I also traded the leased plug-in hybrid for a new Hyundai Kona EV. In 2020 we added another 2 kW of PV capacity to cover all of this new electric demand. This was about $8K before the tax credit.
The final step in 2021 was to add another 10 kWh to the battery capacity. This gives us enough capacity to operate indefinitely if and when the grid goes down, we just can't use the electric stove or oven because their 50 amp circuits were left on the main panel. I think we've had only one half-day planned outage since then. The cost for the battery upgrade was about $20K, before the 28% Investment Tax Credit. We are now saving about $4K per year on propane and replacing it with "free" electricity. And I don't buy any gasoline any more.
So, that's the condensed version of the story. A fairly large investment but a pretty good return, and I was able to take advantage of some major savings. Plus the security of having reliable back-up power. And as retired energy engineer I have a cool toy to play with.