Late to the party here, it was a tough work week.
I have two 5000 watt 220v electric wall heaters, with fans. They are diagonally opposite, so they circulate the air clockwise as they heat. They are both hooked up to the same thermostat, but I can select one or the other. They were nearly free, they came out of a building that was being torn down.
If I spend a LOT of winter weekends in the garage, it costs about $100 extra in electricity over a few months. Maybe $200 in 2016 when we built the new car. No fuel, no CO, no moisture, and no maintenance. I'm OK with all of it.
It's still cold on the floor on a creeper, but great if you're standing. Concrete block, 19 foot square building with an insulated(R30) ceiling and a foam insulated garage door. About 360 square feet. The 8000 BTU window AC unit works perfectly in the summer.
I'll have a radiant heated slab when we move, though.