I think you’ll find the kWh used by any water heater will be negligible, but that the peak kw of the on demand one would force you to buy giant batteries. We e

I think you’ll find the kWh used by any water heater will be negligible, but that the peak kw of the on demand one would force you to buy giant batteries. We ended up getting a hybrid heat pump water heater. It is very efficient, but we have to wait for the water to warm up at the tap. If it were easy to change, I’d probably put in a recirculating system that keeps the water hot in the pipes (not sure how much electricity that wastes though).