I will install solar(not in US) but AFAIK batteries are not yet cost effective, Am I wrong and someone invented some cheap batteries? I expect that a company could be more efficient building giant batteries(chemical, gravity, etc) then a household buying something and maintaining it.
Batteries are not cheap, but they are cost effective based on local conditions.
Time of use billing. The battery is generating ROI if it can arbitrage energy over the day.
Net metering + solar. If net metering is not available, or sufficiently discounted, and your energy usage is not high enough during the day to use all your solar power, then batteries generate ROI.
Grid stability. A battery effectively is insurance against outages of a few hours. With sufficient solar and rationing, that may extend to week long outages (think natural disasters).
I think a solar system that also gives you independence from the grid is much more expensive, the program that we are using to get some subsidies do not include this extra features , so if power is out even if we have solar we still be out of power. Maybe in 10 years or realistically more a more advanced system would be worth it for my situation.
Yes indeed, even a small battery that allows you to shift the late afternoon usage of your house away from the grid will generate ROI by saving you electricity cost compared to a lower feed in tariff during the day.
