Geothermal vs air source heat pump: Which is best?

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If you are looking for an alterative to a traditional air conditioner or furnace, then heat pumps are an option for their energy efficiency. Comparing a geothermal vs. air-source heat pump is one of the first decisions you will make when shopping for a new heat pump air conditioner system.

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Both air-source and geothermal heating costs are much lower than those for HVAC systems, but each has its own clear drawbacks and benefits that you should consider. 

How air-source systems work

During the winter, an air-source heat pump transfers heat from the air outside your home to the air inside your home using a system of coils that remove heat from the air and fans that move the air where it needs to go.

In the summer, the above is reversed. The unit takes the hot air inside your home and transfers the heat outdoors. This involves no fuel, but rather uses a refrigerant fluid to absorb and then transfer the heat where it is needed using a fan.

How geothermal heat pumps work

Geothermal heat pumps take the heat inside the earth and transfer it into your home using water. A geothermal heat pump will transfer the natural heat of the earth into your home to heat it during the winter.

In the summer, it will take the heat from your home and transfer it to the earth to help keep the home cool. 

Geothermal vs. air-source heat pump: energy efficiency

While both geothermal heating systems and air-source heating systems work on the same basic premise, each has its own advantages and disadvantages.

For example, geothermal energy will work better in climates in which temperatures dip below freezing from time to time. That's because these heating and cooling systems do not rely on outdoor units, like an air-source heat pump does.

Both have incredible energy efficiency, require no fuel, and are fairly clean sources of home energy.

Because they rely on water instead of air, geothermal systems do not have to move as much volume to produce the same cooling and heating effect. A geothermal energy system is therefore more efficient.

Geothermal vs. air-source heat pump: resistance to cold

One potential drawback to an air-source heat pump is frost. Water vapor in the air turns to frost at around 34 degrees. Eventually, it creates ice on the fan, which prevents it from pulling air through the coils, causing the heat pump to stop working.

Defrosters can combat this problem, but they add to the amount of energy necessary to run the system.

Because geothermal units rely on water, not air, this does not happen. Antifreeze can combat any problems with frozen water. It does not add to the energy consumption of the system.

Because of its greater energy efficiency, a geothermal heat pump is a better choice when installing a home cooling and heating system in an area where heat pumps work well. However, geothermal heat pump prices, which are up to 40 percent higher than the price of traditional HVAC systems, often cause homeowners to opt for the less efficient, but more affordable, air-source heat pump options.

As you are considering your options for a geothermal vs. air-source heat pump, be sure to call a qualified contractor for an installation estimate and ask about warranty information. When you are ready to hire a contractor to install your system, you'll be satisfied with your decision.

Photo credit: Reinis Traidas via Compfight CC.