Ground source heat pumps (sometimes called underground heat pumps) provide one of the most efficient sources of renewable energy available.
(The other main type of heat pump is an air source heat pump. Read about the differences between ground and air source heat pumps here.)
But what exactly are they?
How do they work?
And are they the right choice for you?
Read on to learn more.
Ground source heat pump: A definition
A ground source heat pump is a category for systems that utilises heat energy from underground to power heating and/or hot water.
There is a common misconception that the term refers to a particular kind of technology.
In fact, multiple types of heat pumps fall under this banner.
Ground source heat pump (vertical)
Every day, the sun’s heat is absorbed by the rock or soil underground. This means that below the surface offers a renewable source of heat.
A ground source heat pump is the technology that you need to extract and utilise this heat. Most use it to heat hot water and indoor spaces.
All heat pumps work with the same principles. A ground source heat pump system consists of a circuitous process of extraction, filtration and expulsion through the pump and into your home or commercial property.
When a ground source heat pump system is installed by drilling boreholes straight down into the earth, it’s called a vertical ground source heat pump.
The ground source heat pump installation process varies depending on the type of pump. It has implications on:
- Applicability
- The space needed
- The cost of installation.
Here are two important elements to note when it comes to your decision to install a vertical ground source heat pump.
- Installation can be expensive. You’re drilling a borehole after all. Having said that, with the available incentives, costs are covered immediately or reclaimed over time.
- Professional groundworks is required. Vertical systems need detailed knowledge about plant equipment, site management, and more.
Installation costs
A 12kW vertical system will cost between £20,000 to £30,000 install.
Vertical systems are always more expensive than the equivalent sized horizontal system, due to the requirement of specialist heavy machinery in the way of the drilling rig to create the borehole.
Each borehole may cost between £4000-£6000 to drill, with additional costs for mobilisation and ancillaries.
Trying to reduce the costs of installation is a risky decision. Poor installation and maintenance can cost you thousands in inefficient running in the years to come.
Ground source heat pump (horizontal)
Horizontal ground source heat pumps require more surface area, as the collector pipes need to be accurately spaced out in trenches.
If you have the land, this may be the best option for you. Here are some key considerations when it comes to horizontal ground source heat pumps.
Horizontal ground source heat pumps are less expensive to install and the operation is typically less disruptive. However:
- Local geological conditions may play a role in whether or not a horizontal ground source heat pump is the right option for you. They are typically suited to wetter areas as this gives them greater heat recovery and ensures the longevity of the system.
- Horizontal systems are not always as consistent as vertical pumps. However, it’s important to note that any efficiency fluctuation over the seasons is usually very small.
Installation costs
A typical 6-8kW horizontal system will cost around £11,000 to £15,000 for the heat pump. A 12kW system for a larger home may cost in the region of £13,000 to £18,000.
The costs for the ground works will be in addition to this. Digging the trenches, although a lot of work, is more economical than drilling a borehole for a vertical system.
If you have the space for a horizontal system, it’s likely you’re situated in a rural area, in which case there may be locals who could help with the initial digging for less than employing specialist contractors.
If you’re starting a new-build project, factoring in these groundworks costs into your overall build budget can help spread costs.
Geothermal heat pump
Now we come to the use of geothermal energy.
It’s vital to note that this type of heat pump does not operate along the same lines as the ground source heat pump options above, and is only suitable to very specific situations.
Geothermal heat comes from the core of the earth. This means drilling to a point where this heat can be accessed.
This is an ideal option for countries that have an active geological framework, where geothermal heat is accessible closer to the surface.
But less active countries like the UK are simply not viable candidates.
The process of installing a geothermal heat pump in the UK is risky, costly and disruptive, and not advisable for most domestic situations.
Running costs of ground source heart pumps
The running costs for your ground source heat pump will depend greatly on your specific situation:
- The size of the system
- The type of property it is used for
- The heat distribution method in place
- How well the system is installed and maintained.
Broadly speaking, heat pumps are the most efficient heating source when compared against traditional methods.
You can be assured that installing a new GSHP is a wise money-saving exercise in the long run, as well as boosting your home’s eco credentials.
The cost savings on fuel is expected when comparing a GSHP to less efficient methods of heating, such as oil, LPG, or electric heating systems.
But the exact running costs differ with every property. Providing run-cost estimates is part of the design process.
Four main factors influence the running costs
These should all be considered before installation. Running costs will depend on the energy efficiency of your home and the heat pump system so you need to consider:
Insulation
Your insulation should be tip-top, with cavities filled if possible and at least 27cm of loft insulation.
Good insulation helps with reducing the size of the heat pump required and ongoing running costs.
After all, if you are heating the outside world it’s costly whatever fuel source you are using.
Heat distribution method
Your heat distribution method needs to be appropriate for a ground source heat pump to ensure it is warming your home most economically.
Underfloor heating systems or specifically designed radiators, which can run at lower flow temperatures, are a must.
Installation
Your ground source heat pump must be installed by an accredited installer, so from the word go, the system can run to its full energy efficient capabilities.
Maintenance
Annual servicing and maintenance work is usually a stipulation of manufacturer warranty – expect to pay around £300 per year.
Systems which are properly looked after will have a longer lifespan and maximum efficiency – and therefore, lowest costs.
The benefits of a ground source heat pumps
Save on your bills
In the UK, the money we spend on our heating and hot water accounts for the vast majority of costs for regular utility bills.
A well-designed and correctly-installed GSHP system could save you money on your heating and hot water bills in many cases.
Fuel cost savings should be expected against oil, LPG and direct electric heat sources.
Provide a safe home
A GSHP doesn’t burn fossil fuels, so you are safe in the knowledge that there is no chance of carbon monoxide poisoning for you and your family.
Be energy efficient
A ground source heat pump can run at up to 400+% efficiency, meaning it produces four times more energy than it consumes. Much more efficient than even the best new gas boilers, which run at around 90%.
Long lifespan
A GSHP has an average lifespan of 20 years when maintained and serviced properly, compared to a traditional boiler which usually needs replacing after 8-10 years.
User-friendly
Using weather compensation, a GSHP can adapt and regulate itself to meet your needs – meaning you don’t have to bother with changing settings or fussing with thermostats. If you want, it can be controlled by a smartphone device for ultimate flexibility.
Decrease your carbon footprint
A GSHP has the lowest carbon dioxide emissions of any heating system when compared to mains gas, LPG, oil or coal boilers, or a direct electrical supply.
A GSHP emits approximately 120kg of CO2 to produce 1000kWh of heat (compared to 450kg for a direct electrical system).
Financial support
The Boiler Upgrade Scheme (BUS) provides vouchers towards the cost of the installation.
The Home Energy Scotland Loan provides interest free loans towards the installation costs as well as 75% cash-back once you have installed.
Summary
Ground heat pump systems are a fantastic renewable energy option for domestic and commercial properties in the UK.
These systems will allow you to reduce your carbon footprint, and significantly reduce running costs for heating and hot water. They are also proven to add value to a property.
Doing proper research is imperative when making the leap to a new way of heating your home.
Understand the implications for each pump type, as well as which installation method may best serve your specific needs. Ground source heat pumps are feasible, affordable, and efficient.
Interested in a quote on a ground source heat pump installation?
Speak to one of our advisors today, and get started on your journey to renewable heating.