Colleagues of mine are working on a system using these kinds of water heaters. Specifically, they are working for a standardized protocol to allow these devices to negotiate prices / indicate to the grid how much they could take.
From what I heard they said something like a half-time for the heat in these devices of about 1 to 2 days.
From what I heard they said something like a half-time for the heat in these devices of about 1 to 2 days.