Goethermal vs. solar water heater efficiency
Hi - I live in Maryland and had a geothermal heat pump system installed in an. 2009 (without a desuperheater). I'm considering a geothermal water "add-on" or a high-efficiency Schuco solar water heater. The stumbling block in the decision process is comparing the efficiencies between geothermal & solar since the geo community uses "Coefficient of Performance (COP)" while the solar guys use"solar energy factor (SEF)". Near as I can tell, they both are ratios between the energy input and the energy output. I suspect that the COP & SEF numbers are not directly comparable -- do you happen to know? The geothermal unit boasts a COP of 6.0 while the solar unit has an SEF of 2.8. If COP & SEF are comparable, then the geothermal unit is twice as efficient - but, if true, is puzzling since the solar unit energy inputs seem minimal since the only electricity needed is for driving a small pump to circulate the water while the geothermal unit has pumps and a compressor. The only thing that I can think of for the relative 'inefficiency' of the solar unit is that it can only heat the water to a point during winter & then relies on the inefficient conventional resistance heater to heat it up to the desired temperature.