Insulate your crawl space
I live in frigid Wyoming (-28 F the past few nights).
Our local power company has a program where for $100 they will do an energy audit of your home. If you follow through with whatever they suggest, they will pay for much of the work, plus give you your $100 back.
We had one done a year ago and they suggested we insulate our crawl space (under the floor above the crawl space...the sides were already insulated). We live in a 1575 sqft ranch house with no basement, only a crawl space. They paid for 80% of the cost to do so.
It has cut our energy bill by at least a third this winter.