I have a 20' x 24' shop built of cinder blocks, no insulation. Since retiring I have started some sub work building cabinetry for a boat contractor. I had sold a pellet stove that was my heat, but needed to get something now and not spend a lot. I researched for quite a while, and this heater kept coming up. I certainly had my reservations seeing the size. Well I bought one and installed it, IT WORKS GREAT. It has been very cold here in Maryland for the last several weeks, highs of 15 degrees and 7 at night. I have not needed to turn it up all the way yet, keeping the heat control at about 2/3rds to 3/4 of the way up. I really don't think you can go wrong with this unit. I still haven't seen my electric bill but according to my calculations it should add about $5.00 a day.