This is a review a did a couple years back but never thought to share it.
Camco 11773 10 Gallon RV Hot Water Hybrid Heat (Automotive)
Dave always turned the hot water heater off in the RV when we were plugged in because it would use more propane every time the water got below a certain temperature. We never could figure out why everything else converted to electricity but not the hot water heater! He saved us a lot of trips to fill the LP tanks and a lot of money, but it was inconvenient! I was sick of coming home after workamping all day and having to wait to take a shower.
I saw this item and thought what the heck, I will try anything! My husband told me that I just wasted our money and told me all the reasons why it wasn't a good purchase.
Because he is a good man, he installed it anyway. He very rarely ever has to admit that he is wrong, but this time he had to eat his words!
Since he installed it, we can go MONTHS without needing to fill the propane tanks. This heater paid for itself in a month! When we are plugged in we ALWAYS have hot water. He put a switch inside the camper so we can turn it on from the inside. We can still use the propane to heat it when we are boondocking.
There is no reason to buy one of those really expensive hot water heaters for your RV, this works awesome and if you are not plugged into electric you can still run your hot water off your propane. This was a great investment and I would highly recommend it to all RV'ers!