Air heat pumps obviously are way less effective when the temps outside are negative. The ground heat pumps work better, but the installation costs are the barri

Air heat pumps obviously are way less effective when the temps outside are negative. The ground heat pumps work better, but the installation costs are the barrier. The silly thing is that even on a sunny winter day an air pump uses a fairly cold air instead of some heated by the sun collector. From what I got such air & sun collector systems are complex to manufacture and maintain, so the more energy hungry air heat pumps dominate.