here, you are legally obliged to push your solarpanel-generated power THROUGH the grid before you get it back (and pay for using the grid + VAT) or else you're a tax-terrorist :D ...
but im not sure sed lex dura lex covers these
https://www.sciencedaily.com/releases/2020/01/200129174512.htm
RE: Dynamo Battery Trickle Chargers - Emergency Radio, Lantern and other Possible Inventions