I've been using this heater to heat a 24x24, 12' ceiling garage. So far I've used it in 30 degree temps and works great! Takes about a half hour or less to make it comfortable. Once I get it to the temperature that's comfortable without a coat, I have to turn it down to about half power. We'll see how it does in a Michigan winter when it's well below freezing temperatures. I'm guessing it will take longer to get heated in the coldest months but will probably maintain the temps well.