Gas furnaces can only approach efficiencies in the mid-90 percent range. Leakage of the potent GWG (Greenhouse Warming Gas) methane from wellhead to your meter continues with gas use, and emissions from burning this fuel are not getting any cleaner. The fuel for heat pumps is electricity, and it's arriving as increasingly green electrons on the way to 100% renewable (nearly everywhere) within a couple of decades. We might remember that renewability means we are on our way to a cost, tax, embargo, emissions and inflation-free system with geo heat pumps.
Geo beats gas for two reasons:
First, Geo taps a thermally stable and plentiful heat source from underground (anywhere) needing no transport to your location. Second, its refrigerant compression cycle provides the best means of thermal leverage available, regularly exceeding 400% efficiency. For cooling, gas furnaces need a separate add-on air conditioning system, operating like a one-way heat pump. Why do THAT for your cooling needs when one piece of equipment (a geo heat pump) can do BOTH?
Geo Heat Pumps (GHPs) beat Air-Source heat pumps (ASHPs) for heating and cooling for two reasons:
First, GHPs access their heat source and heat sink using a looped, circulating liquid that's 3,000 times denser than outside air. It transfers and concentrates the ∆t (temperature difference) between that ground loop's liquid and the underground strata far better while using less pumping power than ASHP fans consume while pushing air. Second, when your insulation can't hold off a cold winter night at 2am and the thermostat calls for heat—GHPs tap a steady underground temperature while ASHPs begin working with the coldest outside air in the daily cycle. And that same disadvantage occurs at 95° in the middle of a hot afternoon.