I have a 24x24 garage that is insulated. I purchased a 240 electric heater that mounts up high, looks just like a gas garage heater. I bought it from NORTHERN Tool co, I have had it for 6 years, my father in law bought the same one 2 years ago, we both love them, I keep my garage set on no3 out of 10 all week long and on weekends I turn it up to 5 as I will work in a t shirt. I live in Ohio with bad winters. My electric bill will rase only by $30 a month.
Here it is, I HIGHLY recommend it.
http://www.northerntool.com/webapp/w...t_6970_595_595