It is a Water heater BTW. The old ones you could set the temp hotter but the new ones are factory set there are a couple of way to pre heat your water like the other poster stated. They make a 110volt on demand water heater that pipes in line it helps or what we have up at the lake on our permanent camper is a roll of pex on the roof of the camper and I put a bypass in and quick connects so it runs through 50 foot of pipe on the roof the sun preheats the water and with a 10 gallon water heater I can take a shower for as long as needed.