One big energy saver is to go easy on the heater. We boondock a lot in semi-cold weather (around 20 degrees -- rarely lower) and we rarely run the heater, except during shower time. At night it can get down into the 30s inside the trailer -- it is very well insulated, but not like an Arctic Fox or a Nash. The secret is a down comforter -- the colder it is inside the trailer, the better we sleep.
We keep some warm clothing with us, under the comforter, so that we can put on a warm layer in the morning before crawling out of bed.
In the evening, even though it is quite chilly in the trailer, we wear warm ski hats and warm clothes. My wife has discovered that a hot water bottle (easily purchased at a drug store) is a great source of warmth -- she sits with a blanket on her lap and a hot water bottle under the blanket. Down booties complete her lovely ensemble.
Is this extreme? Yes. But we use almost no electricity to power the heater. (The propane is no problem - but the furnace fan uses a lot of juice.) And yes, an Olympic heater or other catalytic heater will do the job -- but I am worried (probably needlessly) about carbon monoxide, so we bundle up instead.
Where in Utah do you live? Much of the state is Boondocking Heaven. Let us know, and we can make a lot of recommendations about good areas for camping. You probably already know them!