We are in a 2011 43' Tiffin Allegro Bus with a Hydro-Hot heater parked in the Seattle area, daytime 40's, nighttime 30's. Here is what we are doing. We set our thermostats for Hydro-Hot heating rather than heat pumps. We set the living room to 60 and the bedroom and bathroom to 67, our desired sleeping temperature. We do not have the diesel burner burned turned, on only the Hydro-Hot electric heating element. We have two small cube ceramic heaters in the living room and they keep the temperature there at 72 without any problem. The Hydro-Hot on the electric heating element is capable of keeping the bedroom and bathroom at 67 and the basement at 50, I have a thermometer down in the wet bay so I know the temperature in the basement.
I hope this helps.
2011 Tiffin Allegro Bus 43 QGP