Storage heaters are common in many parts of Europe: https://en.wikipedia.org/wiki/Storage_heater https://en.wikipedia.org/wiki/Storage_heater They already work

Storage heaters are common in many parts of Europe: https://en.wikipedia.org/wiki/Storage_heater https://en.wikipedia.org/wiki/Storage_heater They already work on this principle, more or less: heat up overnight when electricity is metered cheaper, then discharge during the day. There are several companies working on making "smarter" versions that can switch on and off in response to real time data.