Geothermal vs Air Source Heat Pump: Which One is Right for You?

Figure 1: Ground source heat pump unit.

As the world becomes more conscious about the environment, finding ways to reduce carbon emissions has become a top priority. One of the ways to achieve this is by using renewable energy sources to heat our homes. Two popular options are geothermal heat pumps and air source heat pumps.

While both are highly efficient and environmentally friendly, they operate differently and have different installation costs. In this article, we’ll take a closer look at geothermal vs air source heat pumps and help you determine which one is right for your home.

1. What is a Heat Pump?

Before we dive into the differences between geothermal and air source heat pumps, let’s first define what a heat pump is. A heat pump is a device that transfers heat from one place to another. In the case of a home, a heat pump extracts heat from the outside air or ground and transfers it inside to heat the home. During the summer months, it can also work in reverse to cool the home.

2. What are Air Source Heat Pumps

An air source heat pump (ASHP) is a type of heat pump that extracts heat from the outside air. It works by absorbing heat from the air and transferring it into a refrigerant fluid. The refrigerant is then compressed by the compressor, and increases its temperature. Then the heat is transferred inside the home through a heat exchanger. The process is reversible, so an ASHP can also be used for cooling in the summer months.

Figure 2: Air source heat pump working principle diagram.

3. What are Geothermal Heat Pumps

A geothermal heat pump (GHP) is a type of heat pump that extracts heat from the earth. The earth’s temperature remains relatively constant throughout the year, so a GHP can provide consistent heating and cooling.

It works by circulating a fluid through a loop of pipes buried underground. The fluid absorbs heat from the earth and transfers it to a heat exchanger inside the heat pump unit. The refrigerant in the heat exchanger evaporates after absorbing heat and then enters the compressor. After compression, the refrigerant enters the other heat exchanger to release heat to the air or water that is used to heat the building.

In the summer months, the process is reversed, and the GHP extracts heat from the air inside the building and transfers it to the earth through the loop of pipes, providing cooling.

Figure 3: Working principle diagram of ground source heat pump.

4. Pros and Cons of Air Source Heat Pumps

4.1 Advantages of Air Source Heat Pump vs Geothermal

1. Lower installation cost: ASHPs are generally less expensive to install than GHPs. The equipment needed for an ASHP is less expensive, and the installation process is less complicated, which reduces labor costs.

2. More compact system: ASHPs require less outdoor space than GHPs. The outdoor unit of an ASHP is smaller and easier to install, which makes it a more practical option for smaller properties.

3. More flexible placement: ASHPs can be installed in a variety of locations, including rooftops, balconies, and walls. This makes them a great option for properties with limited outdoor space or where underground installation is not feasible.

4. Faster installation: ASHPs can be installed more quickly than GHPs, as they do not require extensive excavation or drilling. This means that the installation process is less disruptive to occupants of the building.

4.2 Disadvantages of Air Source vs Geothermal Heat Pump

1. Lower efficiency in extreme temperatures: ASHPs become less efficient as the outdoor temperature drops, which means they may struggle to maintain a comfortable indoor temperature in extremely cold climates. On the other hand, GHPs are not affected by outdoor temperature changes and can provide consistent heating and cooling with less energy consumption.

2. Noise: ASHPs can be noisy, especially when they are operating at full capacity. The outdoor unit of an ASHP can produce a humming or buzzing sound that can be disruptive to occupants of the building.

3. Shorter lifespan: ASHPs have a shorter lifespan compared to GHPs. The outdoor unit of an ASHP is exposed to the elements, which can cause it to wear out more quickly than the underground loop system of a GHP.

4. Limited capacity: ASHPs have a limited heating capacity compared to GHPs. They may not be able to provide enough heat for larger buildings or for buildings with high heating demands.

Figure 4: Air source heat pump system diagram.

5. Pros and cons of Geothermal Heat Pumps

5.1 Advantages of Geothermal vs Air Source Heat Pump

1. Higher efficiency: GHPs are more efficient than ASHPs, especially in colder climates. Because the temperature of the ground remains relatively constant throughout the year, a GHP can provide consistent heating and cooling with less energy consumption. This results in lower energy bills and a smaller carbon footprint.

2. Longer lifespan: GHPs have a longer lifespan than ASHPs. The underground loop system of a GHP is typically warrantied for 25-50 years, while the outdoor unit of an ASHP may need to be replaced after 10-15 years.

3. More durable: GHPs are more durable than ASHPs. The underground loop system of a GHP is protected from the elements and is less prone to wear and tear than the outdoor unit of an ASHP.

4. Suitable for larger buildings: GHPs can provide enough heating and cooling for larger buildings or buildings with high heating demands. They have a higher heating capacity than ASHPs and can provide consistent heating and cooling with less energy consumption.

5.2 Disadvantages of Geothermal vs Air Source Heat Pump

1. Higher installation cost: GHPs are more expensive to install than ASHPs. The equipment needed for a GHP is more expensive, and the installation process is more complicated, which increases labor costs.

2. Space requirements: GHPs require more space for the underground piping than ASHPs. This may not be feasible for all properties, especially in urban areas where outdoor space is limited.

3. Limited availability: GHPs require a specific type of terrain and geology to be installed, which may limit their availability in certain areas.

Figure 5: Ground source heat pump systems diagram.

6. Which One is Right for You?

When deciding between a geothermal vs air source heat pump, there are several factors to consider. If you live in a colder climate and require consistent indoor temperatures, a GHP may be the better choice. Additionally, if you have enough outdoor space for the underground piping and can afford the higher installation costs, a GHP can provide significant energy savings in the long run.

On the other hand, if you live in a milder climate and are looking for a more affordable option, an ASHP may be the better choice. While its efficiency may decrease in extreme temperatures, it can still provide significant energy savings and a smaller carbon footprint compared to traditional heating methods.

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