When I was working with NREL back in 2017, they were thinking about coordinating water heater electricity use with a “smart grid.” Each device attached to the smart grid would measure the electricity spot price and would “store” energy to minimize cost. At the time the goal was to reduce peak load on the grid, but the same ingredients to maximize power use from intermittent power sources.
For example, see https://docs.nrel.gov/docs/fy23osti/82315.pdf