I have been using this heater in my Grow More 10' x 13' greenhouse for several months, and the temperature had dipped into the lower 20s outside a number of times. The greenhouse temperature has been maintaining around 60 (where I currently want it to be) without any problem. Overall, I am very happy with this purchase.

So far, this heater has done a great job in my small greenhouse. It keeps the space quite warm, and it is very quiet. The coldest it has been outside so far is about 20-25 degree, and the greenhouse has been MUCH warmer than that with this heater.