Heatpump COP vs outdoor temperature curves?
Hi. Earlier this year I replaced my 20 year old gas furnaces with a dual-fuel setup. Currently the HP-gas switchover temperature is set for 40 degrees but finding the proper switchover point really needs to take current energy prices into account as well as knowing the heatpump's COP curve.
Carrier 25HBC324A003 heat pumps
Carrier 58STA070 80% gas furnaces
Does anybody have HP temperature-efficiency data for this setup?
I'm in central KY. Electric rates are around 8.5 cents/KWH and gas prices are currently $5.64/Mcf.
I'm guessing that at these prices, gas will be cheaper at most temperatures:
1 Mcf natural gas = 1,012,000 BTU * 80% AFUE = 809,600 BTU usable
809,600 BTU = 237 KWh of 100% resistive heat = $20.14 at my current rate.
20.14 / 5.64 = 3.57
So the HP only makes financial sense at temperatures where the COP is > 3.57. Any idea what outdoor temperatures that corresponds to?