For typical heatpumps efficiency is a factor of temperature difference. Ground-source are efficient (COP 5) because you go from 5 degrees Celsius to perhaps 35

For typical heatpumps efficiency is a factor of temperature difference. Ground-source are efficient (COP 5) because you go from 5 degrees Celsius to perhaps 35 degree Celsius (underfloor heating or low temperature convection radiators) This invention claims COP 4 for heating water to 80 degrees, that is a huge step up. For instance it changes the game to replace oil and gas heated radiators, as you can only replace the heat source, not radiators that only work well with 80 deg C water (where COP is very bad for conventional heat pumps)