I installed this in a 400 sq ft garage...wired directly using 10/2 to a 30 amp 2 pole breaker. It took a little bit to get up to temp in the garage, but it was 7 deg outside this morning and it was 59 in the garage. I keep it on a middle setting for that and it works for me. I havent see how it is for the electric bill yet so I cant comment on it. Its small, but even with opening and closing the big doors it keeps the temp managable to actually go in the garage and do whatever I need to do. I recommend this to anyone needing to take winters sting off working in the garage.