What is Geothermal Heating in Ireland?

By Cormac Breen

Content Manager

Cormac is Selectra.ie's energy expert along with being the chief content and editorial manager for the website. His aim is to help find the best deal for you and your home energy needs so that you save money on your annual bills. His knowledge and experience of the Irish energy market allows him to offer the best advice and insight into current prices, emerging trends and overall energy saving tips.

Geothermal heating, an efficient process where a Ground Source Heat Pump (GSHP) draws and amplifies the constant 10°C ground temperature for domestic heat, typically costs €17,000 to €35,000 for installation in Ireland before government grants.

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What is Geothermal Heating?

Geothermal heating leverages the thermal energy stored a short distance beneath the Earth’s surface.

Unlike solar or wind power, this subsurface heat is a constant, year-round source, making it an exceptionally reliable form of renewable energy.

How Does a Ground Source Heat Pump Work?

In Ireland, geothermal heating primarily refers to systems that use a Ground Source Heat Pump (GSHP).

The system is designed to exploit the relatively stable temperature of the ground—typically between 10°C and 13°C—a few metres down.

The process involves three essential stages:

1. Heat Collection (The Ground Loop): A network of durable plastic pipes, known as the ground loop, is installed below ground. This is done either horizontally in long, shallow trenches (requiring significant land) or vertically in deep boreholes (suitable for smaller sites). A fluid (water mixed with antifreeze) circulates through these pipes, absorbing the earth’s constant heat.
2. Heat Amplification (The Heat Pump): The warmed fluid returns to the heat pump unit indoors. Here, a refrigeration process—involving an evaporator, compressor, and condenser—is used to compress the low-grade heat, significantly boosting its temperature to a level suitable for central heating and domestic hot water.
3. Heat Distribution: The amplified heat is then circulated throughout the home, typically via underfloor heating systems or larger, low-temperature radiators, to maximise the system’s efficiency.

Is Geothermal Energy Suitable for Ireland?

Yes, geothermal heating Ireland is exceptionally well-suited to the country’s geological and climatic conditions, particularly for heating and cooling applications.

Ireland’s non-volcanic, intraplate setting means it is categorised as a low-enthalpy (low-temperature) geothermal region. While this prevents the large-scale, high-temperature electricity generation seen in places like Iceland, it is ideal for shallow geothermal systems (GSHPs) for domestic use.

• Stable Resource: The ground’s ability to maintain a consistent temperature year-round, regardless of air temperature fluctuations, provides a highly stable and predictable heat source. This contrasts favourably with air-source heat pumps, whose efficiency can drop in extremely cold weather.
• Geological Suitability: The Geological Survey Ireland (GSI) confirms that the vast majority of the island is suitable for shallow geothermal development. Furthermore, the country's mild, maritime climate, with frequent rainfall, keeps the soil moist, making it an excellent medium for heat transfer, which benefits horizontal loop systems.
• Decarbonisation Potential: Given that Irish homes and businesses have a high demand for space and water heating, harnessing this reliable, low-carbon resource is a vital pillar in meeting Ireland’s legally binding climate targets.

Ireland's Deep Geothermal Potential: Beyond Shallow Systems

While the article has primarily focused on shallow geothermal heating via Ground Source Heat Pumps (GSHPs) which utilise the constant temperatures a few metres below the surface, Ireland also possesses deeper geothermal resources. 

The accompanying map illustrates the varying temperatures at a depth of 2 kilometres across the island, providing a visual representation of this deeper potential.

The map, with its colour-coded legend, indicates temperatures ranging from less than 20°C (blue) to over 150°C (red) at 2km depth.

We can observe:

1. Widespread Moderate Potential: Much of Ireland, particularly the central and western regions, shows temperatures in the 31°C to 70°C range (light blue to light green). While not hot enough for large-scale electricity generation, these temperatures are highly suitable for direct-use geothermal applications, such as district heating schemes for towns and cities, industrial process heat, or large-scale agricultural heating (e.g., greenhouses).
2. Higher Temperature Zones: Significant areas, notably in the east and south-east, as well as some parts of the south-west, exhibit warmer temperatures, reaching 91°C to 150°C and even exceeding 150°C in concentrated pockets (orange to red). These hotter zones represent areas with greater potential for higher-grade geothermal applications, including potentially generating electricity, albeit on a smaller scale than high-enthalpy volcanic regions, or for more demanding industrial heating needs. These areas could be particularly attractive for larger commercial developments or for combined heat and power (CHP) projects.

This deeper resource, while requiring more complex and costly drilling than shallow GSHPs, offers the prospect of harnessing substantial, clean energy for a wider array of uses.

Ongoing research and technological advancements aim to unlock this deeper geothermal heating Ireland potential, diversifying the country's renewable energy mix and further reducing reliance on fossil fuels.

The presence of these varying subsurface temperatures underscores Ireland's broader, yet largely untapped, geothermal wealth.

What is the Downside of Geothermal Home Heating?

Despite the substantial long-term benefits, homeowners considering geothermal heating as a home heating solution must be aware of certain key challenges, which primarily revolve around installation.

High Upfront Capital Cost

The most significant barrier to mass adoption is the initial cost.

GSHP systems require extensive civil engineering work, driving the total price substantially higher than conventional boiler or even Air Source Heat Pump (ASHP) installations.

1. Groundworks Expense: The cost of drilling deep vertical boreholes (which require specialised equipment and significant time) or excavating large trenches for horizontal loops forms the majority of the installation expense.
2. Specialised Design: Each system requires a bespoke, site-specific design that considers the unique geology and heat demand of the property, necessitating qualified, professional installers, which adds to the labour cost.

Site and Space Requirements

Geothermal heating is not universally viable for all properties due to site constraints:

• Horizontal Loops: Require a large, unobstructed outdoor area. A typical home may need a garden area 50% to 100% larger than the home's footprint to install the necessary pipework effectively. This is often impractical for urban, terraced, or smaller suburban homes.
• Vertical Loops: While space-efficient, they are the more costly installation option and require access for drilling rigs, which can be challenging on existing, developed sites.

Home Efficiency Prerequisites

For the efficiency advantage of a GSHP to be realised, the house must be well-insulated. The system works most effectively when delivering heat at lower temperatures (35°C to 45°C).

Older, poorly insulated homes will need a full energy efficiency retrofit (e.g., insulation, airtightness, and potentially larger radiators/underfloor heating) to reduce heat loss, which adds substantial supplementary costs to the overall project.

How Much Does Geothermal Heating Cost in Ireland?

The cost of installing geothermal heating in Ireland is high, but grants provide significant financial offsets.

Installation Price Range

The typical all-in cost for a domestic Ground Source Heat Pump installation in Ireland, before grants, generally falls between €17,000 and €35,000, heavily dependent on:

1. System Size: The heat pump’s capacity, determined by the home’s heat loss.
2. Collector Type: Vertical boreholes tend to place the system at the higher end of the range compared to horizontal loops.

SEAI Grants and Financial Support

The Irish Government, through the Sustainable Energy Authority of Ireland (SEAI), offers individual grants under the National Home Energy Upgrade Scheme to make renewable heating more accessible:

Crucially, homes must achieve a B2 Building Energy Rating (BER) or better after the upgrade to be eligible for the heat pump grant.

Homeowners can leverage additional grants for insulation and heating controls to meet this requirement, often as part of the SEAI’s "One Stop Shop" service.

Net Cost Example: A home installing a GSHP and a new central heating system can receive up to €8,500 (€6,500 + €2,000) in heat pump-related grants, reducing the homeowner's net cost significantly.

Is Geothermal Heating Worth It?

For many homeowners in Ireland, the answer is a resounding yes, provided the initial costs and site challenges can be managed. 

Geothermal heating is worth it as a long-term investment due to its efficiency, reliability, and durability.

Operational Savings and Lifespan

• Lowest Running Costs: Due to the stable 10 °C-plus temperature of the ground year-round, GSHPs maintain high efficiency (high COP) even in winter. This means they typically have the lowest running costs of any heat pump technology on the market, generating substantial savings compared to oil, gas, or electric heating.
• Exceptional Durability: Geothermal systems are designed for longevity. The indoor heat pump unit has a lifespan of 20 to 25 years, while the buried ground loop pipework can last 50 to 100 years, requiring minimal maintenance. This drastically reduces the long-term cost of ownership compared to traditional fossil fuel boilers, which typically need replacement every 10 to 15 years.
• Financial Payback: While the payback period depends on energy usage and future energy price volatility, the capital investment is typically recouped through energy savings and grant aid, often within 7 to 12 years.

Environmental and Property Value Benefits

Choosing geothermal heating ensures that a home is completely future-proofed against rising carbon taxes and emissions regulations. It provides a massive reduction in the home's carbon footprint. Furthermore, installing a GSHP and achieving a high BER rating is a major selling point that significantly increases a property's market value.

In summary, for Irish homeowners with the requisite available land or budget for vertical drilling, and a well-insulated property, geothermal heating represents the ultimate, highly stable, and most efficient domestic heating system, delivering comfort and financial returns for decades.

By Cormac Breen

Content Manager

Cormac is Selectra.ie's energy expert along with being the chief content and editorial manager for the website. His aim is to help find the best deal for you and your home energy needs so that you save money on your annual bills. His knowledge and experience of the Irish energy market allows him to offer the best advice and insight into current prices, emerging trends and overall energy saving tips.