The battery in the winter could be used to charge during low cost time periods, assuming your have time of use energy prices. I see people in the UK doing that all the time because the peak prices are very high. I think California is the same.

Batteries have come down a lot in cost, at least the raw ones:

https://youtu.be/3mAx_KE8gz0

Without the tariffs it would be even cheaper I guess.