Aqua Hot is a system, typically used in diesel RVs, that does 2 things, first, it uses diesel fuel to heat a circulating fluid around the coach to various radiators in the coach. Fans on the radiators blow warm air into the rooms, providing heat during cold weather. In addition, the Aqua Hot is used to heat fresh water, in place of a traditional water heater. This feature provides you with almost unlimited hot water. It would be near impossible to install such a system after market due to the elaborate plumbing involved.
Residential refrigerators solve the many problems in propane types. Propane types are slow to cool, and have difficulty keeping cool in very hot weather. Also, propane types demand you keep the frig level when parked. If you read enough posts, you will read about many "fixes" to attempt to correct these faults. Residential frig does not have these faults and work in an RV the same as they do at home, and do not use any more energy.
A few years back, one maker, Norcold, had a design problem in their propane frig that allowed the propane flame to start fires in the coach, causing a number of RVs to burn to the ground. That single possibility is enough to cause me to switch to a residential. No flame!
Finally, if you want more room, you will need a bigger RV. 45ft diesels are very roomy as are the really large 5th wheels.
