The last few nights it has been in the low 20's and we have the View plugged into the house. I have kept the temperature in the coach to around 68 degrees and the Water Heater Hydronic's has had no troubles keeping up. It is nice and toasty in the coach. As others have stated, the cab area really lets in the cold air unless you close that off.
I added the last step yesterday (besides additional insulation here and there) - I added a "computer" fan that blows down from under the shower into the sewer compartment. I hooked up an electronic thermostat controller that will turn on the fan if that compartment is below the set temperature. The controller will also turn on one of the solar circulating pumps to keep the pipes warm and help add heat to under the shower to be blown into that compartment. Worked fine last night.
Now we'll see how it holds up in closer to zero weather - I'm guessing all will be fine based on the system not working very hard in these low 20's temps. Also, once we get snow cover - the cold is more consistent and will test the system a bit more.