Geothermal energy is one of the most efficient and reliable heating options available for Irish homes — but it is also one of the least understood. This guide explains exactly how it works, what the installation involves and what you can realistically expect from a ground source heat pump system in an Irish home.
What is Geothermal Energy?
Geothermal energy is heat drawn from beneath the earth's surface. The ground maintains a relatively stable sub-surface temperature year round — in Ireland typically around 10 to 12 degrees Celsius at the depths used for residential installations — regardless of what the weather is doing above ground.
A geothermal heat pump system (also called a ground source heat pump or GSHP) exploits this stable temperature by circulating fluid through pipes buried in the ground, absorbing the earth's heat and transferring it into your home via a heat pump unit. In summer the process reverses — heat is extracted from your home and rejected into the ground, providing cooling.
The earth continuously replenishes this heat through the decay of radioactive elements in its core and through solar energy absorbed at the surface, making geothermal energy genuinely renewable and inexhaustible at the scales used by residential systems.
How a Geothermal Heat Pump Works
The system has three main components working together.
The ground loop is a network of pipes buried in the ground near your home. A fluid — typically a water and antifreeze mixture — circulates through these pipes, absorbing heat from the ground in winter and rejecting heat in summer.
The heat pump unit is installed indoors, typically in a utility room or garage. It contains a heat exchanger, compressor and refrigerant circuit that concentrates the low-grade heat extracted from the ground into higher-temperature heat suitable for your heating system. For every unit of electricity the heat pump consumes, it delivers three to four units of heat — a coefficient of performance (COP) of 3 to 4.
The distribution system delivers the heat produced by the heat pump throughout your home. Underfloor heating is the ideal distribution method as it operates at the low flow temperatures that suit heat pump operation perfectly. Large area low-temperature radiators are the next best option.
In Winter
The ground temperature at installation depth is significantly warmer than outdoor air temperatures. The heat pump extracts this heat from the ground loop fluid, concentrates it via the refrigerant circuit and delivers it to your heating and hot water systems.
In Summer
The process reverses. The heat pump extracts heat from your home and transfers it into the ground loop, cooling your indoor spaces. This active cooling capability is a significant advantage over air source heat pumps, which struggle to cool effectively in the Irish climate.
Types of Ground Loop Systems
The choice of ground loop configuration depends primarily on the space available at your property.
Horizontal Loops
Pipes are laid in trenches approximately 1 to 1.5 metres deep across your garden or land. Horizontal loops are the most cost-effective option but require significant surface area — typically 200 to 400 square metres of usable ground per 10kW of heating capacity. The ground must be undisturbed after installation so the area cannot be used for building or hard landscaping.
Best suited to rural properties with adequate garden or agricultural land.
Vertical Boreholes
Pipes are installed in boreholes drilled vertically to depths of 50 to 150 metres. Vertical systems require far less surface area — typically just a small footprint at the borehole head — making them suitable for properties without large gardens.
Drilling is more expensive than trenching, so vertical systems have higher installation costs than horizontal systems. However the smaller surface footprint makes them the practical choice for many urban and suburban properties.
Pond or Lake Loops
Where a suitable body of water is available on or adjacent to your property, pipes can be coiled and laid at the bottom of the water source. Water maintains a consistent temperature similar to ground temperature and makes an effective heat exchange medium. This is the least common configuration for residential use but can be very cost-effective where conditions allow.
The Installation Process
Site assessment — a qualified geothermal installer assesses your property's soil type, available space and heating requirements to determine the appropriate system size and ground loop configuration.
System design — the ground loop and heat pump are sized to your home's specific heating and hot water demand. For a well-insulated Irish home of 150 square metres a system of 8 to 12kW is typically appropriate.
Permits — planning permission is not usually required for ground source heat pump installations in Ireland, though it is worth confirming with your local authority for vertical borehole systems.
Ground loop installation — trenches are excavated or boreholes drilled. Pipes are laid, pressure tested and backfilled.
Heat pump installation — the indoor heat pump unit is installed and connected to the ground loop and your heating distribution system.
Commissioning — the system is filled, pressurised, commissioned and tested. Your installer will walk you through the controls and optimal operating settings.
Real World Results: The Murphy Residence, County Cork
The Murphy family installed a 10kW vertical loop ground source heat pump in their 250 square metre home in County Cork. The system was installed by a certified geothermal contractor with partial funding from an SEAI grant.
Results after the first full year included a 60% reduction in annual heating and cooling costs and significantly improved indoor comfort — consistent, even heat throughout the home with no cold spots. The system operates quietly and requires minimal maintenance.
Costs and Grants
Ground source heat pump installation costs in Ireland typically range from €12,000 to €20,000 for a residential system depending on size, ground loop type and site conditions.
The SEAI provides grants of up to €6,500 for ground source heat pump installations through the Better Energy Homes scheme, significantly reducing the net cost. Most homeowners also benefit from a BER rating improvement, which has value both for comfort and for eventual property resale.
Is Geothermal Right for Your Home?
Ground source heat pumps perform best in well-insulated homes — ideally BER B3 or better. If your home has significant heat loss the heat pump will work harder and deliver less efficient operation. Addressing insulation before or alongside installation maximises performance and comfort.
They are an excellent choice for homes currently heating with oil or gas where switching to a heat pump delivers both cost savings and a significant carbon reduction. They are also well suited to new builds where underfloor heating can be designed in from the outset.
If your home is poorly insulated, has no space for a ground loop, or is already on district heating, a ground source heat pump may not be the right fit. An honest site assessment from a qualified installer will give you a clear answer.
Geothermal heating is one of the most efficient, reliable and low-carbon heating solutions available to Irish homeowners today. With SEAI grants of up to €6,500 available, now is a good time to explore whether it is the right choice for your home.