Yep your right there’s only a couple inches depth and width but the 30.2 would be a couple inches too long for his hearth and would need an extension. The 20.2 barely fits and will probably look a little big for the space as it is. He may have to burn a little hotter when it’s below zero with the 20.2 but according to the manual it’s suppose to go 8 hours on high with 30,000+ btu so we’re hoping that will be enough?Check out the 30.2. My house is 1200 sq. ft single story in NorCal and not as cold as you. It's not overkill due to the ability to turn it down. Longer burns. I'm glad I decided on the 30.2. Check the dimensions. 30.2 not much bigger than 20.2 if my memory serves me.