Seems most useful for those with time of use billing for their electricity. And heat pump water heaters can be even more efficient.

There’s a company taking this further in making a fully integrated hot water and home heating heat pump system: https://www.canarymedia.com/articles/heat-pumps/these-new-double-duty-heat-pumps-can-warm-both-air-and-water

Until batteries get cheaper, it could be a better return per $ to look at a system like this.