I'm not them, but recently I've become interested in thermal batteries (aka sand batteries) ala https://www.youtube.com/watch?v=KVqHYNE2QwE which isn't exactly power storage but my house specifically uses 50% of my electricity for the water heater and untold $$$ (and CO2 :( :( ) for the house heater, and thus if I could load up a sand battery with heat and disburse it for hot water and hot air, that'd be swell

Tankless is for sure one fix to that problem, but if I had a magic wand the thermal battery still feels "better" to me