March 16, 2010I use a 4,000 watt electric heater to heat my 23x23 garage with 11 foot ceiling height. Runs on 240 volts. It will raise the temperature about 15 degrees in an hour. Costs about 36 cents per hour to run full blast. It has a thermostatic control, so once it gets to a set temperature, it cycles on and off as needed. Got the heater from Northern Tool for ~$70.00
My garage is attached and there is a room above, so the ceiling is insulated. One wall is common with the house and that is also insulated. The other, outside walls are not insulated. The 2 garage doors were just single wall steel. I added the Owens Corning insulation kits to the doors. That made a big difference.
Oh yeah, no vehicles in my garage, I use the whole thing for my woodworking shop. Both Fords stay outside. For now.