Geothermal Heat Pumps vs. Traditional Heat Pumps
The main concept of geothermal energy is one that’s relatively easy to grasp. For example, the Earth has a constant core of 50°-60°F at all times no matter the temperatures above ground. It makes sense then that we can harness that energy and use it to heat or cool our homes, but here’s where the process gets a little murky – not so much a matter of why, but how?
The two main components of geothermal energy are the multiple tubes/pipes that run underground in the Earth to absorb that 50°-60°F temperature (ground loops) and the heat pump that cycles the radiator/water mix through those tubes. If the tubes are the engine of the operation, then the heat pump does the driving.
What the geothermal heat pump does in the winter is send out cold refrigerant to absorb the warmth of the 55°F temperatures underground. Since 55°F is nowhere near warm enough for winter heat in a majority of North America, the refrigerant goes to a compressor where it becomes a gas upwards of 100°F. This hot gas then rises to a heat exchanger which warms air as it is sent out to the house.
Traditional Heat Pumps
The technology of geothermal heat pumps should sound familiar as it is similar to the methods used in traditional home heating for decades. Traditional heat pumps use an air source to extract warmth from the atmosphere as liquid refrigerant runs through coils in an outdoor unit. An evaporator then turns this heat into a gas so it can release warmth before condensing back into a liquid to repeat the process.
As expected this process loses much of its efficiency as the outside air temperature drops. When the thermometer dips below 40°F there is significantly less heat to pull from the atmosphere so traditional heat pumps are either outfitted with electric resistance coils (like a toaster) or the home features gas back-up. Traditional heat pumps still work well in cooling mode where the refrigerant takes heat from the house and disperses it into the outside environment but most homeowners will want a dual-unit if they spend the time and resources to install a heat pump.
The Major Geothermal Difference
The major advantage that geothermal heat pumps have over traditional units is that their heat source comes from underground (or a deep water source nearby) instead of the air. Unlike an air-source heat pump that struggles with efficiency as the temperatures drop below freezing, a geothermal unit runs as normal thanks to the Earth’s constant 55°F core temperature even in bitter wind chills.
Main Differences Between Geothermal and Air-Source Pumps
While geothermal systems seem to be the way of the future, some people still prefer air-source pumps with their current home setup. The major differences a consumer needs to weigh when selecting between the two include:
- Energy Efficiency – There’s no doubt the most eco-friendly home energy choice is geothermal heating and cooling. The numbers prove it as geothermal heat pumps operate between 300-600% efficiency year-round compared to 175-300% for air-source units.
- Life Span/Maintenance – There are no two ways around it: an air-source heat pump will need to be partially stored outside, which brings along increased risks of damage and the need for cleaning. Geothermal units reside both underground and indoors which limits the maintenance and increases the life span generally. On top of this, the underground units are not subject to the potential damages of air-source heat pumps as they aren’t easily reached. With the exception of natural disasters and, occasionally, tree roots, geothermal systems are not subject to outdoor dangers.
- Costs – Geothermal systems need to be evaluated on total cost of ownership because although the upfront prices are higher (especially excavation for the pipes), the return is recouped in lower energy bills while also being a major selling point when the house goes for sale.
There are many more details that go into the ultimate decision of whether an air-source or geothermal system is right for you (tax credits, property space, existing HVAC setup, etc.).