I agree with Cibula about having 2 or more people to look at the situation. Meanwhile, maybe I can fill in the void or even negate the need for contractors. First, I think of Nevada as mostly desert land, is the 20 degrees considerably lower than your normal temperature?
Heating units are sized according to the cubic space to heat, insulation, the temperate zone and some other things. When all these things are brought together we can come up with a size that will NORMALLY do the job. In order for the unit to be efficient it should not be sized for below normal cold weather. It should even loose a few degrees in extreme weather, especially at night and it should run all the time during that kind of weather. Otherwise, in normal weather it should do a good job, kick off once in a while and keep you toasty warm.
I know that is a lot of rambling but I hope it helps you to understand your system better.