Installing and maintaining a ground source heat pump
In this article we are going to look in detail at the requirements for installing a ground source heat pump for heating and domestic hot water.
We'll cover some of the main considerations such as space and what steps you might want to take to insulate your home for the best savings on fuel costs. Plus, we'll look at the ongoing maintenance required by the system.
Understanding how a ground source heat pump works
The basic principle of a ground source heat pump (gshp) is that heat is harvested from the ground by transferring it to water via a heat collecting loop called a ground collector and then extracted by the refrigerant liquid in heat exchanger of the heat pump for use in heating and domestic hot water.
Unlike traditional boilers which burn fossil fuels, most of the heat energy used by a heat pump to heat your home comes from the sun and is renewable. Because they able to convert a small amount of electric energy into a larger amount of heat they are highly energy efficient.
Unlike ashp's which, whose efficiency is influenced by outside air temperature, a gsph's efficiency depends on the relatively stable ground conditions (or water temperature) surrounding it's collector loop. This means they can harvest heat energy all year round with very little variation in efficiency.
Pre-installation considerations
Firstly, you will need inside space, as a ground source heat pump is usually housed indoors unlike an air source heat pump. Larger properties may have dedicated heat pump plant rooms, particularly where more than one ground source heat pump is installed. Ground source heat pumps are sometimes housed in outbuildings close to the main property to be heated where this is an option.
Domestic gshps have a footprint similar to a fridge or fridge freezer and you will also need space for the associated hot water cylinders - both for heating and also, potentially, hot water storage too. A typical gshp plant room can be accommodated in a utility room.
Don't forget that if you currently have a combi gas boiler, you will also need to find room for a hot water cylinder as ground source heat pumps require them to store your domestic hot water. You may also need room for a buffer tank to store water for your heating system, though this will depend on the system design and is less common for domestic installations.
Secondly, you will need some land outside to install ground loops. We'll go into that into more detail below.
You may also wish to consider combining your gshp with other renewable energy measures such as solar panels to reduce your running costs further - and this should be considered during the planning phase.
It is also important to decide if you require cooling to make sure the system is designed to run efficiently as possible during both heating and cooling seasons.
The image carousel below provides some illustrations of what plant rooms for ground source heat pump installation systems look like.
Plant room images
Types of heat collectors for ground source heat pumps
A ground source heat pump requires a ground loop to harvest the environmental energy for your home's heating system. This can be in the form of a borehole or ground loops and there are several different kinds of ground loops to choose between.
Horizontal ground loops
Land is required for a horizontal ground loop (also sometimes called a ground array) - the coils of pipe containing the liquids that carry energy collected from the ground back to your heat pump to be extracted.
Trenches for this kind of collector are dug into the ground and covered over again. So whilst it is possible to do this in a large garden, disruption to existing landscaping is a consideration. If you are building a new home, it is obviously easiest to plan for the installation of the heat collector loop before the garden or hard landscaping is laid down.
The amount of land required will depend on the amount of energy that is needed to heat your property and the size of the heat pump being installed plus other factors like the quality of the soil in which they are laid. Obviously, the more energy required, the longer the collector loop required. A better insulated home will require less heat and can thus manage with a smaller collector for its size than a poorly insulated one.
How much ground do I need a ground source heat pump?
So how much space is required? As rule of thumb you will need pipework covering at least a 200 square metres. This is achieved by digging a series of trenches dug to a depth of 1.2 metres.
Another often used measure for how much land and you will need is 2 times the square meterage of the property itself. This latter measure is for new build properties with the amount of land required being greater for older properties with at least three or more times the total floor area of the property required (this is both ground and upper floors combined).
Horizontal water source loops
Closed horizontal water loops
The last type of closed collector loop installed with ground source heat pumps is a loop laid in water - either a static body of water like a large pond or lake, or fresh running water like a river or stream. Rarely, this is also done in the sea.
Water is a more efficient at transferring heat to the medium in your collector than earth and so this kind of collector gives high returns. They can be challenging both to install and maintain but can also be less disruptive to lay, as pipes simply need to be laid rather than buried. They can be a great choice if building a new property with plenty of land as a large pond can be created as part of the process of landscaping grounds and the pipes laid during the construction.
Open water loops
The final kind of water collector loop is an open loop where water is collected from a running water source and the heat extracted directly before the water is discharged again, rather than being transferred from a closed loop.
Water extraction like this requires a license and is obviously dependent on approvals from relevant authorities.
Open loops are worth considering if you have a stream or river or even well on your property, but keeping the loop free of debris can increase maintenance requirements.
Thie video below shows a large domestic and commercial installation with an open source borehole
Images and videos of open loops
Boreholes (vertical ground arrays) for ground source heat pumps
The alternative to a horizontal ground loop is a borehole or vertical ground loop. Boreholes are much more space efficient, allowing the use of ground source heat pumps on relatively small plots - but can be costly to drill compared to horizontal ground loops. You will typically need to drill to a depth of 100 metres or more and most homes can be served with ground loops from one or two boreholes.
Access and waste disposal for ground source heat pump installation groundwork
Access and waste disposal for ground source heat pump installation groundwork
Whether you have horizontal or vertical ground loops, with all of this heavy groundwork to be completed an additional consideration is access to the property and disposal of waste material. At a minimum access for a small digger will be required; for boreholes a drilling rig will need to be got into position.
Usually much of the excavated material can be used for backfilling trenches, but it is worth having plans and budget to deal with any excess, particularly from vertical systems.
Preparing and assessing existing homes for a ground source heat pump installation
Do I need to improve insulation for an energy efficient heat pump?
Part of the preparation for a ground source heat pump installation in a retrofit situation is evaluating how much you need and are able to improve existing insulation measures. This is obviously something very much dependent on the existing fabric of the building and any constraints imposed by listing or conservation restrictions.
Government funding can also be contingent on there being no outstanding recommendations on an EPC document (the exact requirements have been changing quite frequently in recent years, so always check the latest information for the funding you are seeking).
It is always a good idea to undertake any simple measures within your means before going to the expense of installing a heat pump system, as increasing your insulation will reduce your bills and may mean you will need a smaller, less expensive system to start with. There's not point paying to generate heat that is lost through leaky building fabric if this is a simple and cost effective fix!
However, it is worth remembering that the key to efficiency with a heat pump is low flow temperatures not insulation. You should not be dissuaded from choosing a renewable system simply because your home is hard to insulate. Your heat pump can be efficient whether or not you install insulation, it will simply use less energy in a well insulated home, which is the same for systems based on oil or natural gas.
Do I need to change to underfloor heating for space heating?
As well as insulation, you may wish to consider upgrading or changing the heat emitters in your heating system. Ground source heat pumps (indeed heat pumps in general) work best and most efficiently with low flow temperature emitters such as underfloor heating and fan coil radiators.
Obviously, installing underfloor heating if replacing an existing fossil fuel system with radiators can be a big undertaking. Fortunately, this is not always essential and in many cases you may only need to increase the size of your radiators as a bigger standard radiator running at a lower temperature can raise the heat in your living spaces just as effectively (though, as with any low temperature heat emitter, such as underfloor heating, this approach to space heating will be slower to respond than radiators running at high flow temperatures).
The installation process
Ground source heat pump system design
The first step towards installing a ground source heat pump is to design the system to ensure that you get the right heat pump to supply the heating requirements of your home. With a new build home this can happen at the stage of architectural drawings to allow enough space to be allocated for all the plant and ground works required.
For properties where a heat pump will displace an existing gas boiler, the design will start with a desk top study and/or a site visit. This will assess the suitability of your home and cover any changes you might wish to make to your existing heating system or insulation you might want to put in place to lower energy bills and reduce carbon emissions.
A system design will be drawn up and costed by your heat pump installer for your approval. Once you have accepted a quote installation will progress at an agreed date. Typically installation takes a couple of weeks from start to finish with all of the ground works, the installation of the pump itself and the associated parts like a hot water cylinder, buffer tank, circulation pumps and controls.
Once a system is complete it should be formally commissioned by your heat pump installer to make sure that it is working correctly to ensure maximum energy efficiency and to validate your warranty.
The costs of ground source heat and available financial incentives
Funding for a ground source heat pump
Ground source heat pumps are typically more expensive to install than air source heat pumps. This largely due to the higher cost of installing a ground loop. It is worth remembering that this is generally a one-off cost as your ground loop should last for many decades - certainly outlasting the ground source heat pump unit itself, in the same way that central heating systems outlast gas or oil boilers.
At the time of writing the government is offering grants in the shape of the Boiler Upgrade Scheme (BUS payment) for ground source heat pump installations. This scheme replaced the renewable heat incentive in 2023.
The boiler upgrade scheme payment is available to homeowners as a one-off grant to cover some of the costs (currently £7500) of installing your ground source heat pump. You can find out more about current funding available for a ground source heat pump on our funding page.
Choosing the right installer for ground source heat pump installation
It is important to find a reputable, well qualified contractor to design and install your ground source heat pump system.
If you wish to take advantage of government incentives your installer will need need to be MCS qualified. The MCS (Microgeneration Certification Scheme) qualification is an indicator that an installer meets stringent training and business quality standards for installing heat pumps.
At STIEBEL ELTRON we can help you find the right installer from our extensive network of trained partners. Simply contact us to talk about your project and we can give you details to contact or even get them to contact you if you prefer.
Maintenance and aftercare for ground source heat pump installations
One of the questions we are often asked is how much maintenance ground source heat pumps require. Heat pumps are generally fairly low maintenance. That said, you should carry out annual check-ups maintain efficiency and validate your warranty.
We can help with servicing by putting out in touch with local service engineers or you can talk to us about our own service packages. Just contact us at technical@stiebel-eltron.co.uk or call our head office for more details.
A typical annual service will include things like cleaning of filters to ensure optimal operation of the heat exchanger, a general review of the operating status of all components, a software update and a review settings for efficient operation and energy efficiency based on the performance of the system in the previous year.
Conclusion
Conclusion
Ground source heat pumps extract heat from the ground or water for heating your home and hot water. A ground source heat pump can be a great investment for a home.
Ground source heat pumps offer a reliable, long-service-life renewable energy solution with the advantages of low running costs and a reduced carbon footprint for your home.
In summary :
Gshps are typically the most efficient and quietest, though more costly to install initially than ashps. The higher initial costs may be offset in future years by lower energy bills. They are most efficient paired with low temperature heating systems.
Ground source heat pumps require outdoor space to install with land required for a ground loop trench or vertical borehole collector though for vertical systems this is minimal. Average gshp installations require 200 sqm of horizontal ground array or vertical boreholes.
Ground source heat pumps also require indoor space for plant as both the heat pump itself and cylinders will be housed indoors.
For new build homes start planning your ground source heat pump installation as early in your planning process as possible to build in space for a plant room and your gshp ground loops.
For homes replacing gas boilers consideration should be given to insulation measures and adapting heat emitters as heat pumps are more efficient at lower flow temperatures and it is easier to achieve the balance between efficiency and comfort with gshp systems in a well insulated home.
But even where further measures to reduce energy usage are difficult it can be possible to have an efficient ground source heat pump system that will result in a lower energy bill and it is worth investigating as an option.