Aqua Hot, Hydro Hot (a slightly smaller version of Aqua Hot) and Oasis (another company) systems all use a diesel furnace to heat hot water and your diesel motorhome. Been told they do an excellent job and you can use electricity to heat the hot water instead of diesel, but to heat the motorhome you need diesel (from the same tank as your engine). Most of these motorhomes come with heat pumps instead of standard air conditioners so above 30 degrees you can heat with electricity when hooked up to 50AMP and about 40 degrees when on 30AMP (our experience).

As furnaces they do a great job and diesel is normally cheaper per BTU (amount of heat energy) than propane, so they save you money. They do take up more room in the bays and inside and every couple years you have to replace an expensive circuit board (over $700 plus labor for someone I know who just did it, it used to be $400), at least for Aqua Hot. They are a bit quieter inside the motorhome, but outside the diesel burner can be noisier and smelly for your neighbors. Most people who have these systems love them, but I know some detractors since there seem to be some lemons out there that break often or act flaky.