I dunno, if electricity was free only for a few hours, I would use it to charge batteries, and then use that stored electricity later in the day when it's not free.
If electricity was free most or all of the time, and/or if I could store more than I could use, then sure, I'd probably use it for unnecessary things that some might consider wasteful (not crypto mining; I'm allergic).
I doubt the economics work, but I'd love to live in a world where a lot of the grid's battery storage is based on backup batteries people have at their houses with the added bonus of reducing their billing costs.
It can be quite profitable from what i heard, in relation to installing solar cells.