Last fall I bought a 12k mrcool DIY for my 12x24 shed. The shed is insulated. Had someone install it, he charged $250, pretty cheap to install. So far I've used it through the winter, haven't had a summer with it yet. I'm in Nashville, the heat on this worked pretty well for a Nashville winter. There were a couple weeks here or there when it got below freezing outside, and then the unit didn't quite cut it. The shed has a barn roof that's 13' at the peak, in the storage loft it was a comfy temperature but in the main part of the shed at floor level it was a little chilly. For Nashville, this was fine, the heat was sufficient for most of the winter. If you're in a place where winter temps are regularly at or below freezing, then you would probably need supplemental heat.