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Ground source heat pumps

What is a geothermal heat pump?

A geothermal heat pump, also referred to as a ground-source heat pump (GSHP), is defined as a heat pump that uses the constant temperature of the earth to transfer heat to and from your home.

How does a geothermal heat pump work?

In the heating mode, GSHP systems transfer heat using a loop system installed in the ground. Heat energy is carried into the home through piping connected to and powered by a heat exchange unit inside the home. In the summer this process is reversed to transfer heat from the home into the ground. A geothermal heat pump may also be used for water heating at no or very little additional cost.

Pros and cons of geothermal heat pumps

Geothermal heat pump systems offer various benefits over conventional heating and cooling systems. That being said, there are also a few things to consider before purchasing a geothermal system. Below, we’ve provided a few advantages and disadvantages of these kinds of systems to help you make your decision.

Pros

Geothermal systems offer several advantages when compared to conventional HVAC systems. Here you’ll find several significant advantages to installing a ground-source heat pump system in your residential or commercial building.

• Uses 25–50 percent less electricity than conventional heating or cooling systems.
• Allows for design flexibility and can be installed in both new and retrofit situations.
• Provides excellent “zone” space conditioning, allowing different parts of your home to be heated or cooled to different temperatures.
• Durable and highly reliable.

Cons

Despite the many benefits geothermal heat pumps offer, the system is not ideal for everyone, depending on your situation. There are some disadvantages you should be aware of before installing a system in your residential or commercial building.•

  • Even though you will save a large amount on your heating and cooling costs each year, the upfront cost to install a ground-source heat pump is significantly more than a traditional furnace and air conditioning system.
  • If your ground loop needs to be located a long distance from your home, the GSHP system can experience energy losses.
  • Some ground loop systems can have significant maintenance costs
  • The installation process can be disruptive and intrusive.

GEOTHERMAL HEAT PUMP COST

Compared to a traditional heating and cooling system, geothermal or ground-source heat pump systems can be costly. On average, you can expect to pay anywhere from $10,000 to $30,000 when installing a new or replacement geothermal heating and cooling system. As a note, this includes the cost of the unit, ground loop and installation.

For larger properties like commercial buildings, you can expect the cost to be significantly higher. However, if you have a smaller home with less demanding heating and cooling needs, you may pay less. The cost of a geothermal heat pump system can be affected by the following things:

Types of geothermal heat pumps

There are four basic types of ground loop systems. Three of these, horizontal, vertical, and pond/lake, are closed-loop systems. The fourth type is an open-loop. Your best option depends on climate, soil conditions, available land and local installation costs at your site.

Ground-source heat pump type: As we’ll discuss below, there are many different options available when choosing a geothermal heating system. Horizontal ground loop systems, the most commonly used system, are generally the least expensive, while vertical loop systems tend to be more expensive.

Quality of your system: As with most things, the equipment you choose for your system can significantly affect the cost you’ll pay for your system. Depending on the system's efficiency and the brand you choose, you can end up paying more for your geothermal heating system.

Insulation and ductwork: If your home doesn’t have properly insulated or sized ducts, you may need to pay extra to retrofit your home with all new ductwork.

Heating & cooling requirements: As you might imagine, larger spaces require more significant heating and cooling loads. Because of this, if you need to heat a larger space, a more expensive geothermal system with higher capacities may be required.

The difficulty of installation: For a professional to install your geothermal heat pump system, they must use heavy machinery to dig trenches or drill wells for ground loops. Depending on your property (layout, soil and rock type, etc.), installation may be more expensive.

What size geothermal heat pump do I need?

Geothermal heat pumps have the potential to be extremely energy efficient, but an improperly sized system can sacrifice your comfort and energy savings. An undersized system will run longer than necessary trying to meet the desired heating or cooling required. The equipment uses more energy in order to constantly run the heat pump, causing your electric bills to spike. And even if it runs constantly, an undersized system will fail to deliver the desired amount of heated or cooled air into the home or building.

Oversized equipment can produce too much airflow, resulting in short run times causing the unit to cycle on and off more frequently than it should. This can cause reduced efficiency and shorter equipment life. It can also lead to reduced comfort since short cycles may fail to reduce the humidity in your home during hot summer months.

Geothermal heat pump sizing calculator

The first step in determining the proper equipment size is to calculate the heat-gain/heat-loss for the home or building. A trusted contractor or your cooperative’s energy advisor can help with these calculations. Your equipment should not be sized solely on the square footage of your house or by your existing equipment size, as it may not have been correct in the first place.

Many contractors will use the Air Conditioning Contractors of America’s (ACCA) “Manual J” calculation, which takes into account several factors (including location, type and number of windows, number and location of doors, insulation type and more) in order to determine exactly how much heat you gain and lose in your home. The recommended system capacity will be specified in either Btu/h (British thermal units of heat removed per hour) or refrigeration tons (one ton being equal to 12,000 Btu/h).

Geothermal heat pump terminology

Coefficient of Performance (COP): A measure of efficiency for ground-source heat pumps in the heating mode, that represents the ratio of total heating capacity to electrical energy input. The larger the number, the less electricity the unit uses.

Compressor: The central part of a heat pump, the compressor pumps refrigerant to meet the heating or cooling requirements of the system.

Energy Efficiency Ratio (EER): A measure of efficiency for ground-source heat pumps in the cooling mode that represents the ratio of total heating capacity to electrical energy input. The larger the number, the less electricity the unit uses.

System Capacity: A measurement of the total amount of heat or cooling your system can produce in one hour.

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