More food for thought. As much as I love the econ-omy of a heat pump in a temperate climate, 'pumps don't like temps down into the teens. Cold attracts heat, so, the outdoor compressor works always at 20 degrees colder than the air temp outside. It goes into a defrost mode every few hours, to keep ice buildup on the grill at bay. At 20 degrees outside, the compressor is actually working at 0 degrees. Any lower and suplemental heating MAY be needed. Hope this works out for you, Charlene.