Heat tape would work well, no pun intended. They don't draw a lot of amps so a good extension cord would work if the pump house is within 100' of the outlet. I used them on the hose and frost free hydrant when I was living in my trailer while building the house. I put the heat tape on the hydrant and hose and then used the big thick pool noodles to insulate above the tape. Cold, rain, and snow didn't bother it and they only heat to about 50* before the thermostat cycles them off, usually they cycle on at 40*. They don't get hot enough to cause a fire concern.
For best results block any air gaps in the pump house to retain as much heat inside as possible. If you use your water regularly, or drip a faucet, the water from underground would be warm enough to prevent freezing on most days, but it is better to be safe and prepared for the cold spells.
) middle of the night stuff, feeding the wood stove and taking Bear out for a pee! 11° and a north wind at the moment!
