Well, the efficiency of a heat pump/refrigerator is limited by Carnot's theorem. Essentially it boils down to the difference of the outside temperature compare

Well, the efficiency of a heat pump/refrigerator is limited by Carnot's theorem. Essentially it boils down to the difference of the outside temperature compared to inside temperature. With an indoor temp of ~72F and outdoor ~90F the maximum efficiency is a COP of about 30. Current AC units are in the 2 to 4 range. So a 30% increase doesn't seem impossible that low on the efficiency scale. There was a recent similar jump in efficiency when the US raised the minimum SEER standards for new systems from 10 to 13.