Scottaw wrote:mine were still putting out heat at -10,
Yup, yup, I've heard tell they will make heat when it's somewhere near stupid cold outside, BUT... as the temp drops they become less and less efficient. I'm thinking my AC guy said they approach zero....meaning, at some very low outside temperature, they are very close, or the same as, a resistance heater.
For those units that don't have a resistance heater built in.... Go buy a $39 oil filled electric heater. Not cheap to use, but cheaper than frozen pipes.