the house i am at has a 4500 watt 66 gallon hot water heater. the water is generally heated to hotter than i need it and ive always wondered how much energy it took to maintain that temperature. there is no temperature control on the heater. so i go to home depot to look at hot water heaters and find something startling - there aren't any. 'tankless' or instant hot water heater units are connected to just before the shower and just before the sink. it sounds like a more efficient system.