Some times the temperatures can drop to -20 or lower here. What should I do to prepare?

I was thinking about moving his viv to the bedroom, which is the smallest room in the apartment, and getting a space heater with digital thermostat and keeping the room at somewhere around 76-80 (warm enough for his tank to properly heat itself and not so hot that I drown in my jammies). Oh gawd my electric bill is gonna rock my face.