I just purchased one of the overhead electric heaters like shown in the ad for Northern on page 11. I used it with a kerosene topedo heater hooked to a thermostat a week ago to keep the stuff in my garage from freezing. My garage is 24 X 34 and isn't completely insulated (only half done with that), but does have drywall in the ceiling. I set the thermostat at 55 deg for the kero unit and let it run for a week. The kero heater only used about 1 gallon, and we had some pretty cold days/nights for us. I got a second electric heater for Christmas, and hooked it up (tough job, it plugs in). It was about 30 deg yesterday, and the temp in my garage was about 57 deg. If the place was completely insulated, and I covered the holes in the ceiling and around the AC unit, I am sure that they would heat it really well. I didn't get mine from Northern, they came from Lowes, at $50.00 each.
I don't know what it is going to cost me for this heat out there. I hope that the electric bill is such, that my wife feels it is cheaper to pay for the rest of the insulation and drywall. If not, I will get it done with the addition that I am getting ready to put on.