Geothermal = “Green”
Geothermal heat pumps are nationally known and have been proven to be the most environmentally friendly heating, cooling, and hot water systems available today. Here are a few quotes from outside agencies that have tested the effects on the environment of a ground source heat pump system.
“Geothermal Heat Pumps are recognized as the leading space conditioning technology in all locations & from most perspectives – operating performance, annualized cost, environmental impact & attractiveness to utilities as a DSM measure” (U.S. EPA report 430-R-93-004)
“Geothermal Heat Pumps have a higher mitigating effect on Green House Gas emissions and global warming impacts than any other market-available technology” (NRCan market analysis)
Some have argued that because a geothermal heat pump isn’t 100% renewable and uses electrical energy that they are not as good for the environment. This is assuming that a coal fired generation plant was utilized to produce the electricity used. Minnesota is leading the United States in it’s diversity of electricity generation with systems such as wind, biomass, and others. So with that said, what if the electricity being used was produced by a wind generator? Doesn’t that make the system 100% renewable?
Let’s look at the other side for a moment which would be using fossil fuels to heat your home or business. A furnace, whether it is a LP or Natural gas, burns a fossil fuel, and because they aren’t able to achieve 100% combustion, you have some green house gas emissions from that furnace into the atmosphere. A geothermal heat pump has no spot or direct emissions into the atmosphere since there is no combustion. One thing that isn’t mentioned about furnace technology is that all furnaces need electricity to operate the fan motor and combustion motor. So add that to the equation as well, granted it is less than a heat pump, but it still needs to be added into the overall emission’s generated. Then factor in the efficiency of the water heater and air conditioner and the emissions generated with those devices because a geothermal heat pump provides all three. A water heater (gas fired) will have spot emissions from burning a fuel, and the air conditioner uses more electricity during the summer than a geothermal heat pump (see how it works page) due to the efficiency of the device. 
The geo-exchange heat pump will provide free waste heat in the summer for water heating which has zero emissions associated with it, and then provide some hot water during the winter months at a COP of a minimum 3.5, so that equals using 1/3 the electrical energy needed, and figuring in what type of generating plant is used would determine the amount of emissions produced. Overall, the ground source heat pump system has no spot emissions, and uses much less electricity than the other electric driven options for air conditioning and water heating.
Another aspect to look at is from the generation view point. There have been many studies done on different types of electric generation and their respective emissions. However, there haven’t been as many studies done for fossil fuels and what emissions they have regarding generation. To make a fair comparison from a geothermal system to a fossil fuel system wouldn’t you need to take it from source to end use? Most of the reports done on geothermal systems vs. conventional hvac systems figure a coal fired generation plant for geothermal, but only figure the unitary furnace for the conventional side, which isn’t a fair comparison because there are no emissions factored in on the source of the fossil fuel. 
Whether it is Propane or Natural gas, it also has to be developed, refined, and distributed. What would you think the emissions are on 1 pound of propane that was drilled for in the middle east, sent to the United States as crude oil, refined into LP, sent out to distribution point, and then delivered to the homeowners tank? How about natural gas that is drilled in the gulf coast, refined, pumped from there to a substation in the midwest, and then out to the home? Yes, generating electricity produces green house gases, but so does all forms of energy generation. So a true comparison would only be one of two ways, from source to end use of each system, or just taking the unitary piece of equipment and it’s emission potential. With that being said, the geothermal heat pump has Zero spot emissions vs. some spot emissions for the conventional furnace, which is unknown due to lack of studies done.
