1. On demand RV are LP only
2. I am a RV service tech and I would NEVER/EVER have one in an RV. They have way too many problems and Tiffin motorhomes have dropped them as an option because of the complaints. They have continuous too hot, not hot enough or rapid pulsating from hot and cold. They have to have a specific water pressure all the time and INPUT water temp is a big factor in correct operation.
3. They are a continuous source of service headaches. Precision Temp and Girrard both have the same problems, regardless of any product updates they claim to have done or provide. Doug