> Your tankless water heater is a good example of something that is completely inadequate for solar setups, they draw insane amount of energy over very quick period

I know nothing about any of this, so please educate me for the good of us all - wouldn't this logically be a use case for a battery? IE: solar (or wind or whatever...) feeds a battery that feeds the tankless water heater. As a layperson, it would seem to me like the issue isn't generation but rather availability at the moment of demand - which would be the case in any kind of micro generation, right?