3 ms·Also water heater using a heat pump is 200-500% efficient.by jnsaff2 6y agoAlso water heater using a heat pump is 200-500% efficient.SigmundA 6y agoNot going to heat instantly using a heat pump, it would be tank based and it needs solar heated air (warm outside or warm garage).jnsaff2 6y agoI don't understand what you are saying. There are air to water heat pumps as well as ground source heat pumps. Both have typically tanks.