I have electric baseboard heat in my garage and I wouldn't recommend it. My garage is 24x24 and well insulated and the electric heating is expensive in the winter. At one point in the winter I was heating to 17 degrees and for that month my bill increased from around $300 per month to just over $1000. I would recommend a natural gas heater if you can easily get a gas line to your garage. Otherwise I would recommend a propane heater with a larger tank outside of your garage. This is what I have been considering but haven't gotten around to upgrading.
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