What about sand batteries? They're cheap, safe, scalable, extremely durable, and they can take advantage of dynamic pricing (or intermittent energy sources). Th

What about sand batteries? They're cheap, safe, scalable, extremely durable, and they can take advantage of dynamic pricing (or intermittent energy sources). They are easy to connect to an existing heating system. They're relatively new, but a few companies are making them now and there's a LOT of handy homeowners playing with that tech right now.