How do you know if should upgrade your air-conditioner to a heat-pump and create a dual-source application during replacement this Summer? I personally always prefer the option of multiple fuel sources, particularly since energy prices have been all over the place during the last decade. Fortunately, based on average energy prices, there is some simple math to figure out if an aggressive assessment should be made for a dual-source heat pump application, based on equations from ACCA's Manual H: "Heat Pump Systems: Principles and Applications". First, you will need the average energy costs for the selected fuels, and then plug in the information into the equations below. This will provide your "break-even COP", or the point where operating the heat pump will cost the same as the furnace. You can then take the calculated Coefficient of Performance (COP) and see what temperature the heat pump will be operating at; the lower the better!
With the recent technological advancements in the HVAC industry in controls and conventionally ducted VRF's like the Carrier GreenSpeed, break even COP's and Thermal Balance Points can be driven even lower. This makes Dual Source Heat pump applications more attracting to New England homeowners. Some contractors are still installing electric supplemental heat, hopefully in stages, for low-ambient operation. Although not any more efficient than the heat strips it replaced, the new heat pumps could save more than enough above the temperature of the defrost cycle to still be worth it. I would still prefer dual-source, you know these energy companies will not be leaving any money on the table over the long run!