Geothermal Heating vs. Ground Source Heat Pumps, What’s The Difference?

What’s The Confusion?

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The terms "geothermal energy" and "ground source heat pumps" (GSHPs) are often used interchangeably - especially in North America, where GSHPs are commonly referred to as “geothermal heat pumps.” Understandably, this has led to some confusion.  

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Technically, both GSHPs and deep geothermal systems fall under the umbrella of geothermal energy because they tap into heat from the Earth. But in the UK, the term “geothermal” is generally used to refer to deep geothermal systems: those that drill kilometres into the ground to access high temperatures for district heating or electricity generation. GSHPs, by contrast, work much closer to the surface - mostly solar energy absorbed by the ground - and are designed to heat (or cool) individual buildings or small networks efficiently.

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So, while both technologies harness natural ground heat, their source, depth, and usage differ significantly. Let's take a closer look at the two and break them down…

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(Deep) Geothermal Energy

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Geothermal energy harnesses the immense heat generated deep within the Earth's core, where temperatures can soar to around 6000ºC. Deep boreholes, typically ranging from 500 to 2,500 metres in the UK, are drilled into the ground and filled with water to access this heat.

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As the water circulates through the borehole, it absorbs heat from the surrounding rock, turning into steam or hot water. This thermal energy can then be used directly for heating as well as generating electricity by driving turbines. In regions with high volcanic or tectonic activity, such as Iceland and New Zealand, geothermal energy is more accessible due to naturally occurring hot springs and geysers, allowing for shallower drilling and more efficient extraction.

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With an estimated lifespan of 4–5 billion years, geothermal energy is a virtually inexhaustible and sustainable resource, making it a key player in the transition to renewable energy.

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Ground Source Heat Pumps (GSHPs)

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Unlike deep geothermal systems, which tap into heat from the Earth's core and convert it into electricity, a GSHP extracts ambient heat stored in the ground or water just below the surface, typically at depths of around 100-300 metres, and uses it to heat or cool buildings.

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This stored heat isn’t from the Earth’s interior - it’s solar energy that the Earth absorbs throughout the year. Even in winter, temperatures remain stable below the surface. At around 15 metres deep, the ground maintains a consistent temperature, which in the UK is roughly 8–11ºC, according to the British Geological Survey.

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A GSHP system consists of underground pipes filled with an antifreeze solution that absorbs heat from the surrounding earth. This fluid circulates through a heat exchanger, transferring the warmth to a property's heating and hot water system, providing year-round reliable, renewable energy.

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Common Misunderstandings

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GSHPs and geothermal power are not the same. In North America, GSHPs are often called "geothermal heat pumps," which can be misleading. While GSHPs use geothermal energy in a broad sense, they do not generate electricity like deep geothermal systems. Some also believe GSHPs only work in hot regions, but they function effectively in a wide range of climates by tapping into stable underground temperatures, even in the depths of a cold UK winter. Finally, deep geothermal and GSHPs can coexist. The deep geothermal industry sometimes overlooks the benefits of GSHPs, but both technologies contribute to reducing carbon emissions.

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Practical Applications

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Deep geothermal can be used for large-scale power generation and district heating. In the UK, reaching temperatures of 100°C requires drilling around 3–4 km underground.

“Average UK subsurface temperatures at 1000 m, 3000 m and 5000 m are around 40°C, 90°C and 140°C, respectively, which is sufficiently high enough to provide heat directly for space and hot water heating without requiring a heat pump. In some parts of the UK, temperatures within economic drilling depth (approximately 5 km) are high enough for electricity generation.” - British Geological Survey (BGS).

GSHPs are ideal for homes, commercial buildings, and industrial facilities. They require less drilling and provide an efficient way to heat and cool buildings without the need for fossil fuels.

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Key Stats

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• Depth differences: Deep geothermal systems require drilling 3000–4000 metres below the surface in the UK, while GSHPs operate at depths of around 100–300 metres.
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• Carbon savings: GSHPs can reduce heating-related carbon emissions by up to 70% compared to traditional fossil fuel systems.
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• Efficiency gains: GSHPs achieve a Coefficient of Performance (COP) of 4 or higher, meaning they provide four units of heat for every unit of electricity consumed.
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• Cost differences: Deep geothermal systems have higher upfront costs due to deep drilling and complex infrastructure, while GSHPs are more affordable.

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Final Thought

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So, in conclusion, both deep geothermal and GSHPs are important for the future of clean energy, but they serve different purposes. Deep geothermal focuses on large-scale power and heating, while GSHPs offer an efficient solution for both individual buildings and shared heat networks across multiple properties.

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When considering GSHPs, it's crucial to understand the technology and its long-term advantages to make informed decisions that positively impact both the environment and your finances. Whether you're working on a new build, a large commercial development, or a retrofit, GSHPs provide a sustainable and cost-effective solution.

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To explore how ground source heat pumps can enhance your project, get in touch with our expert design team.