Open Loop vs. Closed Loop Geothermal Explained

Geothermal Energy: Open Loop vs. Closed Loop Systems

Geothermal energy is a sustainable and efficient way to heat and cool buildings. It utilizes the Earth’s stable underground temperatures to transfer heat. There are two main types of geothermal systems: open loop and closed loop. Understanding the difference between these systems is crucial when considering which one suits your needs. Let’s get into comparing open loop vs closed loop geothermal systems.

When working with a professional geothermal installer like ACES Energy, your installer will recommend the best system for you. In Western NY, the majority of our installations are closed loop based on our professional recommendation to our customers.

Geothermal loopfield system diagram open loop and closed loop
The various available geothermal heat exchanger loop types. Note: Typical systems only have 1 type of loopfield. This diagram is for demonstration purposes only.

What is Geothermal Energy?

Geothermal energy is heat derived from the Earth’s interior. It can be used for heating, cooling, and generating electricity. A geothermal heat pump or ground source heat pump (GHP/GSHP) is a device that uses this energy to heat and cool buildings. These systems are becoming increasingly popular due to their efficiency and environmental benefits.

To learn more about the differences between geothermal energy types and heat pumps, check out this blog article:

Open Loop Geothermal Systems

An open loop geothermal system, also known as a “pump and dump” system, uses groundwater as a heat exchange fluid. Here’s how it works:

  1. Water Source: The system pumps groundwater from a well or a body of water.
  2. Heat Exchange: The groundwater passes through a heat exchanger, transferring heat to or from the building.
  3. Discharge: The water is then discharged back into the ground or a surface water source like a pond.

Advantages of Open Loop Systems:

  • Efficiency: Open loop systems can be highly efficient because groundwater temperatures are relatively constant.
  • Lower Installation Cost: They can be cost effective to install if there is an adequate water supply nearby that does not require drilling or extensive trenching.

Disadvantages of Open Loop Systems:

  • Water Quality: Geothermal heat pumps requires clean, abundant water. Poor water quality can damage the heat pump system.
  • Maintenance: These systems can require more maintenance to prevent clogging and scaling from minerals in the water.
  • Water Availability: In the case that your water source depletes over time, your system can decrease in efficiency. The water source and flow must meet the minimum gallon per minute requirements of the geothermal system to operate.

Closed Loop Geothermal Systems

Closed loop horizontal geothermal loopfield being installed

A closed loop geothermal system circulates a mixture of water and antifreeze through a closed network of pipes buried in the ground. The three main types of closed loop systems are horizontal, vertical, and pond/lake loops.

  1. Horizontal Loop: Pipes are laid out horizontally in trenches dug typically by an excavator. This is suitable for areas with plenty of land.
  2. Vertical Loop: Pipes are installed in vertical boreholes. This is ideal for smaller properties or where soil conditions are not suitable for horizontal loops.
  3. Pond/Lake Loop: Pipes are submerged in a nearby body of water. This is only possible if there is a suitable water source.

Advantages of Closed Loop Systems:

  • Durability: Closed loop systems are more durable and have a longer lifespan.
  • Less Maintenance: They generally require less maintenance than open loop systems as the geothermal components are not subject to varying outdoor water sources. When installing a closed loop system, we are able to control water quality.
  • No Water Quality Issues: Since the fluid is contained within the pipes, there are no issues related to water quality.

Disadvantages of Closed Loop Systems:

  • Land Requirements: Horizontal loops typically require 1+ acre of land depending on the required capacity of your heat pump. The loopfield size is based on the size of the geothermal unit.

Open Loop vs. Closed Loop: Which is Better?

When comparing open loop vs. closed loop geothermal systems, several factors need to be considered:

  1. Cost: Open loop systems may have lower initial installation costs, but they may incur higher maintenance costs. Closed loop systems are more expensive to install but have lower operating and maintenance costs over time.
  2. Efficiency: Both systems are efficient, but open loop systems can be more efficient due to the direct use of groundwater. However, this depends on the availability and quality of the water source.
  3. Environmental Impact: Closed loop systems are generally considered to have less environmental impact since there is no water discharge. Open loop systems can affect local water sources and require management.
  4. Land Availability: If you have limited land, a vertical closed loop system or an open loop system may be more suitable. Horizontal closed loop systems require a large area for installation.

Common Problems with Geothermal Systems

Both open loop and closed loop geothermal systems can encounter problems:

Open Loop Geothermal Problems:

  • Scaling: Minerals in the water can build up in the system, causing blockages and reducing efficiency. If you have hard water and do not have a filtration system in place, you can prevent these issues by choosing a closed loop geothermal system.
  • Water Availability: An adequate and sustainable water supply is crucial. Dry spells or overuse can deplete the water source.

Closed Loop Geothermal Problems:

  • Leaks: While very rare, leaks in the closed loop system can occur, leading to loss of loop fluid. Our loopfield systems come with a 55 year warranty against manufacturer defects, and our team tests your loopfield upon installation. Closed loop piping systems have shown to last 50-100 years and do not need to be replaced when you replace your geothermal heat pump.

Choosing the Right System

To choose between an open loop and a closed loop geothermal system, consider the following:

  1. Land Area: For properties with limited space, vertical closed loop systems are more suitable. If there is ample land, horizontal loops could be considered. If you have an available pond, a pond loop may be best. Open loops are only available in specific applications where the resources are available.
  2. Long-term Costs: Consider the long-term maintenance and operating costs. Closed loop systems typically have lower ongoing costs.
  3. Environmental Impact: If minimizing environmental impact is a priority, closed loop systems are generally better.


Both open loop and closed loop geothermal systems offer efficient, sustainable heating and cooling solutions. The choice between them depends on factors like water availability, and land space. By understanding the differences between open loop and closed loop systems, you can make an informed decision that meets your needs and contributes to a greener future.

At ACES, we provide our customers with our professional recommendation that would be best fit for your installation.




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