How does a geothermal heating system work?

Geothermal heating systems are becoming more common as they are a low-carbon alternative to heating homes now and in the future. we’re going to look at how a geothermal heating system works, the pros and cons, and the potential savings.

What is a geothermal heating and cooling system?

A geothermal heating and cooling system that uses the heat in the ground as a source of energy. Through a system of pipes and a heat exchanger, heat can be transferred to radiators and other climate control systems in your home and provide hot water. Many of these systems can also be used to provide geothermal cooling in warmer weather – a greener alternative to air conditioning.

The ground just under the surface remains at a fairly constant temperature throughout the year. This means that using a geothermal heating system to take energy from the ground to the home makes it possible to maintain a comfortable temperature in your home all year round.

How does a geothermal heating system work?

Geothermal heating systems work by pumping water containing antifreeze (called glycol) around a loop pipe that is buried under the ground in your garden. The length of loop pipe you need depends on how large your home is and what temperature you want to maintain in your home.

As the glycol solution passes through this loop it picks up heat from the ground. This heat energy is then passed through a heat exchanger into a heat pump, also known as a ground source heat pump.

Green heating systems are now available that run these heat pumps using power generated by renewable sources such as photovoltaic solar panels, meaning they don’t have to rely on mains energy and are an environmentally friendly option. Find out more about renewable energy by reading our blog about green energy technology.

Geothermal heating system design

When it comes to geothermal heating system design there are three main considerations:

• Heat loss/gain calculations
• Size of the heat pump
• Size of the loop field

When calculating the system design the first step is to work out how much heat needs to be generated to heat the home, and the size of the heat pump required.

The next step is to check the local deep earth ground temperature. Following that, a decision needs to be made between a vertical or horizontal installation of the heat pump. Vertical pumps tend to be deeper and more costly to install but can provide a more stable temperature. Horizontal installation is more common in rural areas where there is more space to lay long loops of pipework.

There are other considerations but a ground source or geothermal heating specialist will calculate all of this for you and explain what is required.

Electrical trace heating

Ground source heat pumps do contain electrical resistance wires that provide emergency heat if the outdoor temperature drops to -6 celsius or lower.

Geothermal heating system cost

Geothermal heating systems are a significant investment and are between £10,000 to £20,000 to purchase and install (this would cover the horizontal ground loop or vertical borehole only. It would not cover the supply or installation of the heat pump or other property upgrades required). As a geothermal heating system owner, you will also need to account for annual servicing costs, which can be around £300.

Take a look at our ground source heat pump cost guide for more information.

Average cost saving of a geothermal heating and cooling system

For an average UK home, the running costs are typically around £650, and typically very little maintenance is required. If the system is kept in good health, it could last more than 20 years. The pipe loops in the ground can last for up to 70 years.

Depending on your current heating energy source and provider, you could save over £400 per year in comparison to gas-fired heating, £600 or more per year in comparison to oil-fired heating, around £1,000 per year if you switch from LPG heating, and potentially up to £1,200 per year if you currently have traditional electric storage heating. (Source: Energy Savings Trust, based on April 2022 gas and electricity rates).

For more information on the cost of Geothermal heating systems and information about The Renewable Heat Incentive (RHI) take a look at our ground source heat pump cost guide.

Geothermal heating system reviews

As with any heating system, there will always be pros and cons. Here is a summary to help you decide if a geothermal heating system might be right for you:

Pros

• Significant annual savings on energy bills
• Environmentally friendly
• Suitable for most climates
• Less noisy than air source heat pumps
• Low maintenance
• Longer lifespan

Cons

• High upfront installation costs
• May involve a lot of landscaping alterations
• Open loop systems can risk local groundwater
• Local ground conditions can affect energy output
• Horizontal heat pumps require a large amount of space

If you’re looking for a greener alternative for your home heating and see this as an investment for your property and the future of the environment then a geothermal heating system is most definitely an attractive option. For more detailed information about ground source heat pump prices read our ground source heat pump cost guide. If you’re considering a geothermal heating system then speak to a local specialist who will be able to advise you.

FAQs

How long does geothermal heating last?

Typically the ground source heat pump can last for as long as 20-25 years, and the pipe loops for up to 70 years – as long as the system is checked and maintained regularly.

Do you need backup heat with geothermal?

For general home heating, you should not need additional heating in your home to keep it warm. You can talk to your heating specialist about the flow rate of your geothermal system which has a part to play in keeping your home warm if you have a ground source heat pump.

Ground source heat pumps do contain electrical resistance wires that provide emergency heat if the outdoor temperature drops to -6 Celsius or lower.