Electric heat is horribly inefficient and one tgat size will be noticeable on your electric bill. Like Jason said it all depends on your total use but I would put electric heat at the bottom. I think that one of those torpedo heaters like Dan has that runs on propane, kerosene, diesel, ect. Is a better option. I think that wood heat is the best for a garage if you use it pretty often. We have a barrel stove in my dads shop at home and it works great for the size of our shop.