Recently, I met with a local architectural designer for lunch and we were discussing how one might go about decreasing their carbon footprint. Most people would think solar panels, right? When we looked at the numbers, geothermal was the winner by a landslide.
Suppose we take a typical home in New England that has oil heat – say 2,500 square feet of conditioned space. Let’s compare the carbon footprint reduction associated with solar PV panels and a geothermal heat pump system. We used the US EPA Household Emissions Calculator as the basis for our back-of-the-envelope calculations.
It is likely that the home would use about 1,000 gallons of home heating oil each year which is equivalent to 22,300 lbs of carbon dioxide. The geothermal system would use about 8,000 kWh of electricity which is equivalent to 6,700 lbs of carbon dioxide. The net reduction would be 15,600 lbs of carbon dioxide (~70% reduction) just for heating alone.
Solar PV panels are simply replacing one source of electricity for another. This ‘typical’ home could possibly install a 8 kW system which is roughly equivalent to producing 6,600 kWh of electricity each year. The PV system therefore results in a net reduction of 5,500 lbs of carbon dioxide.
Clearly, eliminating fuel oil has a much larger impact on your carbon footprint that offsetting your electricity use with solar panels. Of course, using solar panels to offset your geothermal electricity use would be the ultimate green combination!
If you would like to calculate your own carbon footprint, try out the US EPA Household Emissions Calculator. Let us know how your home rates!