I don't heat my snake room for the same reasons cost of power. I have fl lights inside my enclosures and LED over night. I often run in the winter the LED string 24/7 and the FL 12 on and 12 off. This with insulation give me 10-15º over the ambient temps. You might get a few more degrees from a RHP I'd try the FL lights first as they are cheap. It is a real issue I had a higher power bill that you currently have the steps I have taken dropped it from 400-500$ an month back to 60-75 a month.