Guide to Ground Source Heat Pumps

Today, the drive to do away with fossil fuel-based heating and electrical generation has never been higher and due to this many new technologies are emerging to replace them and one such technology is that of ground source heat pumps.

With this in mind, in this guide we take an in depth look at these heating systems and how they work and whether you should consider such an item in your home.

Ground Source Heat Pumps – A Quick Overview

Ground source heat pumps use the Earth’s natural heat to warm your home. Pipes buried in your garden draw heat from the ground, which stays at a stable 12°C year-round even at depths of only 1m or so.

This heat is then used to power radiators, under-floor heating, and hot water systems. Modern systems adjust to outside temperatures, ensuring efficient heating even in cold weather.

Switching to a ground source heat pump could save you around £1,000 a year on energy bills if you currently use electric heating.

How Ground Source Heat Pumps Operate

Ground source heat pumps use a “ground loop” of piping buried in your garden to extract heat from the earth. If space is limited, the loop can be installed in vertical boreholes.

• A water-antifreeze mixture circulates through the ground loop, absorbing heat from the earth.
• The warmed fluid then passes through a heat exchanger, transferring its heat to a refrigerant.
• The refrigerant is compressed to raise its temperature, making it hot enough to heat water for your home.
• The cooled fluid returns to the ground loop, where it picks up more heat and repeats the cycle.
• The length of the ground loop depends on your home’s size and heating needs. A longer loop extracts more heat but requires more garden space.

Other types of heat pumps work on similar principles but use different sources:

• Air Source Heat Pumps: These extract heat from the air outside. They are cost-effective and easy to install, ideal for urban areas with limited space.
• Water Source Heat Pumps: Similar to ground source pumps but use water from lakes or rivers as the heat source.
• MVHR (Mechanical Ventilation and Heat Recovery): This system captures heat from outgoing air, making it efficient in well-sealed homes.

Different Types of Ground Source Heating System

Ground source heat pumps are an increasingly popular renewable energy solution for heating and cooling homes or buildings. As we have touched on, they work by tapping into the natural warmth stored beneath the earth’s surface, providing an efficient and sustainable alternative to traditional heating systems.

There are several different types of ground source heating system, with each being suited to a particular type of home or installation. Here follows the most common types:

Closed-Loop Systems

Closed-loop systems are the most common type of ground source heat pump. They use a continuous loop of plastic tubing buried underground, filled with a water-antifreeze mixture that circulates to absorb and transfer/capture heat. There are three main ways to install closed-loop systems:

Horizontal Closed-Loop System

A horizontal system is ideal when there is sufficient land available. It involves burying pipes in long, shallow trenches, typically 4 to 6 feet deep. This system is cost-effective but requires a large amount of space, making it suitable for rural areas or properties with large outdoor spaces.

Vertical Closed-Loop System

For properties with limited space, vertical closed-loop systems are a better fit. With these, deep boreholes, ranging from 100 to 400 feet, are drilled, and the pipes are inserted vertically. Vertical systems tend to be more expensive to install but are more efficient for properties with limited ground space or when there’s minimal disruption to the landscape.

Pond/Lake Closed-Loop System

If you have access to a nearby water source, a pond or lake system can be used. The loop is placed at the bottom of the water body, where temperatures remain relatively stable. This option is highly efficient and generally less expensive because it requires less digging, but it does depend on having a suitable water source nearby.

Open-Loop Systems

Open-loop systems differ from closed-loop systems in that they use groundwater or surface water directly. Instead of circulating fluid through a closed loop of pipes, these systems draw water from a well, lake, or pond, use the water to transfer heat, and then return it to the source.

Open-loop systems are very efficient because water is an excellent conductor of heat. However, they require a steady supply of clean water and are subject to local environmental regulations. If your property has access to a reliable water source, this could be a more affordable option compared to closed-loop systems, but you must ensure that your water supply is adequate and sustainable over time.

Hybrid Systems

Hybrid ground source heat pumps combine different technologies or energy sources to optimise efficiency.

For example, a hybrid system might combine a ground source heat pump with a traditional boiler or a solar thermal system.

This setup can reduce overall energy consumption and provide more flexibility, especially in areas with extreme seasonal temperature changes. Hybrid systems are often tailored to individual needs and can offer cost savings in both installation and long-term energy use.

Installing Ground Source Heat Pumps

In England, Scotland, and Wales, you generally don’t need planning permission for ground source heat pumps. However, always check with your local authority to be sure. Common locations for installation include utility rooms, basements, or garages.

The ground loop is typically laid in trenches about 2 meters deep. For a standard home, you’ll need roughly 600 feet of pipe. A typical setup for a 2-bedroom house requires two trenches, each about 12 inches wide and 45 meters long, spaced 5 meters apart. Trenches should be level and in moist soil for better heat conduction. If garden space is limited, the loop can be installed vertically up to 10 meters deep.

Ground Source Heat Pump Installation Checklist

Here’s what to consider for a successful installation:

• Ground Loop Installation: Ensure you have enough level space for the ground loop. If space is limited, consider a borehole, but make sure machinery can access the area.
• Home Insulation: Your home must be well-insulated and draught-proofed. Ground source heat pumps operate at lower temperatures than traditional boilers, so good insulation is crucial for efficiency.
• Existing Fuel Source: If you use electric, solid fuel, or oil heating, a ground source heat pump can offer significant savings. Savings will be smaller for homes with gas heating.
• Heating System: For best results, use larger radiators, under-floor heating, or low-temperature fan convectors. These are more efficient with the lower temperatures produced by heat pumps.
• Other Projects: Combining heat pump installation with other building work can reduce costs.

Heat pump efficiency is measured by the Coefficient of Performance (CoP), which indicates the ratio of heat output to electricity used. Higher CoP values mean better efficiency, with some pumps providing up to 4 kW of heat per kW of electricity.

Another metric, the System Efficiency Ratio (SER), shows the overall efficiency of the heating system. The SER typically ranges from 1 to 4, with ground source heat pumps averaging around 2.3-2.5, and the most efficient reaching up to 3.3.

Ground Source Heat Pump Installation Time

Installation time for a ground source heat pump varies based on the system size and any additional building work being done. Combining the installation with other projects can reduce costs and impact the overall timeline.

Ground Source Heat Pump Installers

To qualify for government incentives like the Renewable Heat Incentive and Renewable Heat Premium Payment (both unfortunately ended for new applications now), ensure your installer is MCS accredited. Only MCS-certified installers can validate installations for these schemes.

Ground Source Heat Pump Costs

Ground source heat pumps typically cost £8,000 to £24,000 to install, with vertical systems costing up to £49,000 (roughly 3 times more than a horizontal installation). Running costs depend on your home’s size and insulation. Switching from oil or electric heating can save you over £610 annually.

Government schemes may offer partial or full funding for your installation, however not many of these now exist. One that does at present is the Boiler Upgrade Scheme, which offers up to £7,500 towards the installation of both air and ground source systems.

Unlike oil or gas boilers, heat pumps run at lower temperatures for longer periods. To optimise efficiency, keep the system running continuously in winter. This approach is essential for effective operation.

Benefits of Ground Source Heat Pumps

Switching to a ground source heat pump can save you over £610 annually on heating bills, though savings vary based on your current system. You may also receive a £1,250 Renewable Heat Premium Payment and quarterly payments for the heat you generate if installed by an MCS accredited installer (new applications for such schemes has now unfortunately ended). Additional benefits include:

• Reduced Carbon Emissions: Heat pumps lower the amount of fuel burned, decreasing your home’s carbon footprint.
• No Fuel Deliveries: Heat pumps run on electricity, eliminating the need for fuel deliveries.
• No Boiler Needed: Unlike traditional systems, heat pumps don’t require a boiler to boost hot water.
• Low Maintenance: Heat pumps are ‘fit and forget&rsquo technologies, needing minimal upkeep.

Ground Source Heat Pumps – Maximising Your Savings

To get the most savings from your ground source heat pump, consider these factors:

• Heat Distribution: Underfloor heating is more efficient than radiators because it operates at lower temperatures and covers a larger surface area.
• Current Heating System: The less efficient your existing system, the greater your potential savings with a heat pump.
• Hot Water Usage: Using the heat pump for hot water can reduce its efficiency. Installing a solar thermal system can help supplement hot water in warmer months.
• System Usage: Heat pumps are more cost-effective when used continuously throughout the day. You can lower the thermostat setting while maintaining comfort due to the consistent temperature.

If you are looking at reducing your heating costs and also doing your bit to reduce your environmental impact then installing a ground source heat pump in your home is a great way to go and give you savings that you will actually notice.