Heat pumps, geothermal and AC
Heat Pump Efficiency explained - The definitive guide to SEER vs HSPF vs (S) COP Heat Pump Ratings
...ratings were born, starting with:
COP ratings for heat pumps
COP ratings came along much earlier than SEER or HSPF ratings, as the theory behind "heat engines" first became a subject of debate and experimentation after Nicolas Léonard Sadi Carnot - a French engineer - came up with the theoretical concept of the "Carnot...