I put a tankless water heater under the kitchen sink in my house (not my A/S - still looking for a trailer
). We had to run the hot water for an inordinate amount of time to get hot to come out, so I added one of these to speed things up. It basically is a heated coil of pipe which the water runs through - nearly instant hot water. It works great at home, but I saw a post mentioning that most trailer parks have limited amperage to the sites, so this could be an issue as they draw quite a lot. The main benefit is having an endless supply of hot water - with no waiting... I've had it for a couple years now with no problems or leaks.