Comment by ben_bai

In short: Sand for industry scale heat storage, water for private heating storage.

Using a heat pump will increase the yield. Usable temp range from 95C water all the way to 0C ice in theory (latent heat).

And a modern isolated home helps, but seasonal heat water storage is basically a big tank, with a house build around it.

https://www.energie-experten.ch/de/wissen/detail/waermespeic...