Ground Source Heat Pumps Guide

Are you looking for a more sustainable way to heat your home? Installing a ground source heat pump could be the answer. While reliance on fossil fuels decreases, renewable energy solutions will be in greater demand as those in the UK push to meet the energy-efficiency 2050 deadline.

What is a ground source heat pump?

A GSHP consists of a series of pipes, also referred to as ground loops, that lead to a plant room inside of the home. Highly efficient, this setup can help you to save money on home-energy costs while reducing your carbon footprint. A ground source heat pump can be used to replace a boiler in heating your home and for providing hot water.

The sun is a powerful source of energy. Unlike solar panels that typically require direct sunlight or air source heat pumps that need a proper ambient temperature, the ground source heat pump absorbs warmth from the ground after it’s been heated by the sun. Temperatures below the surface remain fairly stable even when air temperatures change.

How it works

Pipe loops buried beneath the surface of your garden carry a water and antifreeze mixture that absorbs ground heat at low temperatures, gently warming the liquid within the pipes. This liquid then moves to the heat pump and passes through an exchanger, also referred to as an evaporator, where it then heats up a refrigerant liquid that turns into a gas at the appropriate temperature.

The cooled antifreeze mixture returns to the ground to begin the heat-extraction process again. The refrigerant gas moves to a compressor where it’s pressurized and heated even more. This hot gas makes its way to a condenser where it increases the temperature of water within pipes that are used to provide heat for your home.

Once the gas loses its heat, it transforms back into a liquid. This liquid refrigerant moves to an expansion valve where it loses pressure so that it can be returned to the exchanger to begin the process again.

Efficiency

While a small amount of electricity is required when using this setup, a ground source heat pump produces up to four times more energy than it uses. This translates into reduced paid energy consumption and lower power bills. If you qualify for the Renewable Heat Incentive Scheme, or RHI, you could actually make money off of any extra energy your system produces.

As an added bonus, energy produced by a ground source heat pump can also be used to cool your home during the summer months, saving you even more over an electrically run air conditioning system.

If you don’t have close access to a mains gas line, it can definitely be more efficient in the long run to install a ground source heat pump that lets you stay off-grid rather than resorting to the high cost of using electricity alone.

It’s important to note that your costs may be higher if you use this system for hot water, which then reduces the overall efficiency. One way that you can save is to combine your ground source heat pump with solar for heating your water.

Common types

Depending on the size and layout of your property as well as the amount of heat that you need to produce, there are a few layout options available.

Horizontal ground loop

This is the most common layout used and is best suited for larger plots of land. Pipe loops are buried 1M to 2M deep and run parallel to the ground surface, maximizing the amount of pipe to ground surface area for more heat to be absorbed.

Vertical borehole

If you’re limited on space, the vertical layout may be your best option. Pipes are inserted into boreholes that can run from 15M to 200M deep. The depth and number of the boreholes depends on how much heat you need to produce for your home.

Closed loop pond or lake

Water holds heat from the sun similar to the way the ground does. If there’s an underwater pond or lake nearby, the pipes can be laid at least 3M below the surface to extract the heat.

Open loop

An open loop system is much less common due to limitations in water supply in the UK. Instead of using pipes filled with antifreeze and water, open pipes extract water from the source to the heat exchanger.

The installation process

The heat extracting pipes or pipe loops will be buried beneath the ground’s surface before being attached to newly installed heat exchangers and the heat pump. If you’re replacing your current heating system, you may have to purchase larger radiators or have underfloor heating installed as well.

Depending on the chosen layout for your ground source heat pump, actual installation may vary. For a horizontal layout, trenches of about 2M deep will be dug out in the width that’s required for your system. The loops of pipe will be laid then buried.

If you’re having a vertical system installed, boreholes of up to 200M will be created. The pipes will be inserted into these holes, which are then filled with grout to absorb additional warmth from the ground. Insulation should be placed around the pipes to at least the 6M depth mark. You’ll need to hire a specialist contractor to dig the necessary boreholes.

Closed loop pond/lake systems will have a supply line buried in the ground that leads to the water source. The pipe loops are laid in the water and held at the appropriate depth with weights. The body of water should be at least 0.2 hectares in area and about 3M deep to adequately heat an average-sized home.

Is planning permission required?

In most cases, you won’t need to get planning permission to have your heating system replaced with an eco-friendly ground source heat pump. However, since there are certain cases where a permit may be required, it’s best to check with your local planning commission before any actual installation work begins.

Furthermore, you’ll need to register your ground source heat pump with the Distribution Network Operator, or DNO. Whether this will need to be done before or after installation will vary. Typically, your installer will complete the necessary registrations, so be sure to ask.

Is a ground source heat pump easy to maintain?

Although your ground source heat pump should last at least 20 years, annual maintenance is recommended for longevity and appropriate efficiency. This is especially beneficial if you qualify for programs such as RHI that requires proof that your system is functioning effectively.

All above-ground components should be inspected, including the mechanical and electronic elements, connectors, and the antifreeze-water mixture. You can perform much of the inspection yourself each year as long as you have a professional come check every few years. Ask your installer about the specific items you should check on a regular basis.

Additionally, you’ll want to have your ground collection loops flushed and refilled about every eight years or as recommended by the manufacturer or installer.

Most systems come with two- to three-year warranties on the components of the system while some warranties for workmanship can last for 10 years. You may be able to purchase extended protection.

Cost

The initial purchase and installation for your ground source heat pump is where you’ll spend the majority of costs. Some of the factors that will influence how much you’ll pay for your system include the following:

Size of the home you’re heating
Amount of heat you’ll require, such as for both heating and for hot water
Area of land available
Type of layout – for example, vertical systems cost more to install than horizontal
Composition of the soil
Sufficiency of insulation in your home
Addition of underfloor heating or larger radiators

It’s estimated that the average cost for a ground source heat pump and installation ranges from £14,000 to £20,000. Any of the above-listed factors can increase the actual cost that you’ll have to pay. However, this initial investment can be recouped in about seven years on average for most homeowners.

The running costs for your ground source heat pump will vary based on your utility company and the energy source that you plan to replace. For example, a ground source heat pump may average 4.7p/kWh while all-house electric may cost 15.0p/kWh.

Financial incentives may be available

If you qualify for the renewable heating incentive, you could earn money quarterly for seven years on the energy produced by your ground source heat pump. You could earn up to £21.00 for every kWh produced, which translates into about £15,000 over the course of seven years. However, this number can vary greatly depending on the size of your home and other factors, so you might want to check out the Renewable Heat Incentive calculator to get an approximate idea on how much you can get.

Pros and cons

As with all sources of energy, there are some pros and cons that you’ll want to take into consideration before making your purchase.

Pros

Here are some of the major benefits that you’ll enjoy with a ground source heat pump:

Lower heating bills
Reduced carbon footprint
Quiet operation
Minimal maintenance
Longer life of components
Safer than other forms of power generation
Double benefit of heating and cooling
Renewable energy source

Cons

Unfortunately, there are some disadvantages that you may encounter if you switch to a ground source heat pump for energy:

High initial investment
Large areas of ground need to be dug up, which is highly disruptive
Lower temperature heating requires more or larger radiators, air heating and possibly the installation of underfloor heating
Specific geology may be necessary for certain systems
Antifreeze and water mixture is not safe for the environment, so a skilled professional needs to install the coils or pipes to avoid leakage

Is a ground source heat pump right for your home?

While it’s more cost effective and easier to install a ground source heat pump for a property that’s being newly built, it’s still a great choice for upgrading your current system to one that’s more eco friendly. However, there are several key considerations before you get started.

Insulation

Because a ground source heat pump uses lower temperatures to heat your home when compared to other energy sources, it’s imperative that your home is well insulated and free from draughts. A home that is not insulated properly won’t see much in the way of cost savings and may not obtain a comfortable temperature during the winter.

Plant room

The main unit of the ground source heat pump in installed inside of your home. The space needed is more than that for an airing cupboard that’s used for a boiler. You’ll need to make sure that you have enough space to house the unit, which is typically about 2M by 1M.

Available outdoor space

Your property needs to be big enough to hold the ground loops whether you’re using the horizontal or vertical layout. There also needs to be access for the excavators to bring in the digging equipment that’s needed for installation. Additionally, the composition of your soil must be suitable for the proper digging to occur.

Reason for updating your heating system

If you have an older home that requires upgrades, such as underfloor heating, your cost savings may not be considerable if you’re already hooked up to mains gas. However, if you use other sources of energy, the long-term savings can really add up. Thus, it really depends on your current source of energy and how extensive the needed upgrades will be to determine if a ground source heat pump will actually provide you with savings overall.

On the other hand, if you’re looking for a greener way to live by switching to a more sustainable source of energy or wish to stay off grid, a ground source heat pump could be just what you’re looking for.