Checked this morning before going to work. Unit is at expected temperature. 1/6 of my propane to do it.
I have a heat pump at home. I did my research on that one, and it's effective to about 20 degrees outside before activating emergency heating.
I know that the Duo-Therm units on my coach are what's offered, and I can't easily spec ones that work in a wider temperature range. I also know that due to the size of the units that the performance will not be as high as my home heat pump. Just figured it would take a bit longer to hit the requested temps.
Mind you, if I had natural gas service at home, I'd make that the emergency heat source in a heartbeat. When it gets sub zero, I could make heat off the friction from my electric meter.