With a goal set for the UK to be net zero by 2050, it’s no surprise that the Government has begun to encourage homeowners who have previously only known a fossil fuel-powered system to consider renewable energy. Air source and ground source heat pumps are accessible examples, and there’s a lot to learn about them. They’re becoming more and more commonplace in homes across the nation, both as part of new builds, and retrospective installations.

As a heat pump installer with a wealth of experience in installing and servicing air and ground source heat pumps, we love sharing our knowledge with those looking for greater efficiency from their heating system, and make a positive impact on the planet.

In this article we’ll be exploring what an air source heat pump and a ground source heat pump actually is; how they’re installed, the pros and cons of each, and what help you can get to fund their installation.

First, let’s take a look at some statistics, which demonstrate well the growing appetite for air and ground source heating in homes over recent years: 

  • There are currently 412 heat pumps for every 100,000 people in the UK
  • In 2021, the UK heat pump market almost doubled
  • As part of its energy security bill, the UK government has plans to install 600,000 heat pumps per year by 2028
  • The energy produced from heat pumps can be up to 4x more efficient, with 73% less carbon emissions than even the most efficient boilers.

What is an air source heat pump?

Air source heat pumps cleverly extract heat from the air (even in sub-zero temperatures) and allow you to use it to heat your home through radiators, or through underfloor heating. This efficient form of heating is a low carbon alternative to gas boilers, which are more expensive to run, and operate at a greater cost to the planet. Air source heat pumps are occasionally referred to as air-to-water source heat pumps. 

How does an air source heat pump work? 

Using a coil filled with liquid refrigerant, which circulates at -28°C, air source heat pumps extract the heat from the air, which heats this liquid and converts it into a gas. This gas is then compressed, increasing the temperature further, before being released through the indoor heating system and water heating facilities through another coil. The gas then cools, returns to its liquid form, and returns to repeat the process.  

If you have an air source heat pump installed, you’ll find that your radiators do not get as hot as they would if they were powered by a gas or oil-fired boiler. This is because efficiency has increased, which means that they can produce heat effectively without getting as hot, gently heating your home. 

How are air source heat pumps installed?

The good news is that air source heat pumps can be installed both on new builds, and retrofitted to properties that have, up until now, been heated via traditional methods. In any case, you must use an experienced Microgeneration Certification Scheme certified installation contractor – this is no time for DIY! 

For the purpose of this guide, we’ll be using a retrofitted air source heat pump as an example. 

In general, the whole installation process will follow the following three-part structure: 

Pre-installation assessment for Air Source Heat Pumps

To get the ball rolling, an engineer will need to come to you, and assess your property’s suitability for an air source heat pump installation. Air source heat pumps have an internal unit, and an external unit, and this external unit needs to be somewhere that has a solid concrete base, good drainage, and sufficient airflow around it – it won’t work well if there are obstacles. 

At this visit, the engineer will also get to grips with the existing heating system, making note of the way in which appliances such as gas boilers would need to be safely removed, and how the heat from the pump itself would get around. Air source heat pumps can be connected to radiators, underfloor heating (which is ideal for ultimate efficiency), or even air conditioning units. 

Once these assessments have been made, the engineer should be able to give you a recommendation for the best type of air source heat pump for your property, and how much it will be to buy and install. 


Air Source Heat Pump Installation

Installation will usually take 2-5 days, as draining down and removing the old system before installing the new air source heat pump will take a little while. Both internal units and the external units need to be connected up through an outside wall, and any upgrades you’re making to your hot water system, radiators or underfloor heating will naturally add more time to the install. 

A good air source heat pump engineer will be able to talk you through the process, keep you informed at every stage, and conduct their work safely, cleanly, and with as little disruption as possible. 

Post-installation and maintenance for
Air Source Heat Pumps  

Once the equipment is in position, secured and connected up, there are just a few finishing touches to be made, such as installing the pump’s sensors that will talk to your thermostat. 

Your installer should run through how everything works, answer any questions you may have, and talk to you about a maintenance schedule. 

What are the advantages of an air source heat pump?

It uses a renewable energy source

Sustainability isn’t just a buzzword – it has fast become a necessity. The use of fossil fuels such as gas to heat homes is damaging the planet through carbon emissions, whereas an air source heat pump is powered by a renewable source with a low carbon footprint. 

It’s energy efficient

No one likes waste, and thanks to their coefficient of performance (COP), air source heat pumps  produce more heat energy than they consume, which could see you saving money on your energy bills. Air source heat pumps are generally around 300% efficient, which means that on average, your air source heat pump produces three units of energy for every unit of electricity it uses. In comparison, most electric boilers are, at most, 98%-100% efficient. 

You can enjoy both heating and cooling 

No, it’s not just you – our summers are getting hotter. In 2022, temperatures of 40 degrees celsius were recorded in the UK, but for those with air source heat pumps, this was eased by their system’s ability to cool their house too. 

They’re eligible for the Boiler Upgrade Scheme 

To incentivise the upgrade of heating systems by homeowners to replace their fossil fuel-powered heating system to an eco-friendly version, the UK Government can contribute to the cost of an air source heat pump. See the UK Government Boiler Upgrade Scheme website for more details. 

They’re low maintenance

Air source heat pumps are generally low maintenance, but we would still recommend a regular once over from an air source heat pump professional. This will include ensuring that the air source heat pump is clean and unobstructed, cleaning the filters, checking the refrigerant levels, and ensuring the whole system still works efficiently and reliably. 

They last a long time

A properly maintained air source heat pump can last anywhere between 15-25 years. When you consider that the average gas boiler lasts between 10-15 years, you can see how the air source heat pump comes up trumps. 

What are the disadvantages of an air source heat pump?

They’re dependent on electricity 

Air source heat pumps sound like an off-grid option, but they still need electricity, so unless you’re generating this in a renewable way too, you’ll still need to rely on an electricity provider in the normal way. 

You may need to upgrade your heating 

Because air source heat pumps have a lower heat supply than fossil fuel-powered systems, the surface area they need to emit heat from needs to be larger, so you may need to invest in an underfloor heating system, or bigger radiators. 

Your home needs to be well insulated in the first place

The heat that an air source heat pump produces is wasted if your home isn’t well insulated, although this is true for any other heating system too. 

They can be noisy 

Depending on the size of your house and where you have the air source heat pump installed, their operation can be noticeably noisy. It’s a similar level of noise to an air conditioning unit. 

Higher installation costs

Getting an air source heat pump installed can be more expensive than another heating upgrade, but the good news is that you may be eligible for a Government grant, and the savings in energy costs should balance out the initial outlay. 

Less effective in lower temperatures 

An air source heat pump can extract heat from the air in temperatures as low as -25 degrees celsius, but obviously it will be lower. If you live in an area with a temperature that’s lower than average, you may want to look at low-carbon alternatives. 

What to consider when you’re thinking about getting an air source heat pump 

How suitable your home is 

  • Is there a hardstanding for the air source heat pump outside your home?
  • Is your home well insulated?

Funding 

  • Will you need to upgrade your home’s heaters, such as installing underfloor heating or buying bigger radiators?
  • Would you be eligible for Government grants to contribute to the cost?

Installation 

  • Are you prepared for the disruption of installation?
  • Are you able to find a Microgeneration Certification Scheme certified installer?

What is a ground source heat pump?

Just like the air source heat pump extracts heat from the air, ground source heat pumps extract heat from the ground, converting it into usable energy with which you can heat your home. It’s another low-carbon way to heat your home using underfloor heating and/or conventional radiators.

How does a ground source heat pump work? 

Ground source heat pumps work by using a system of buried pipes, known as a ground loop, to extract heat from the earth. Inside the ground loop, you’ll find a water-based solution called thermal transfer fluid (TTF), and this absorbs the natural heat from the ground. The heat is then carried to the internal heat pump unit, located inside the building where the heat will be used. 

Once it’s reached the heat pump unit, the heat is amplified and transferred to either the building’s heating system, or to the domestic hot water supply. 

Ground source heat pumps can provide both heating and cooling solutions; to cool a building, the process is simply reversed; the heat pump removes heat from the building and takes it back into the ground to dissipate.

How are ground source heat pumps installed?

First, it’s important to understand that the systems buried underground can be horizontal or vertical; horizontal systems are laid in relatively shallow trenches in the ground where there’s enough space (usually at least half an acre of land, with trenches dug between 1m to 2m deep). Vertical systems require boreholes to access the heat deeper within the ground, and these can be at depths of anywhere between 15m and 122m. 

Similarly to its air source counterpart, ground source heat pumps can be installed both on new builds as well as houses that have previously used a different heating system. Again, this is not something you can tackle yourself; ground source heat pumps need to be installed by an MCS-accredited installer.  

For the purpose of this guide, we’ll be using a retrofitted ground source heat pump as an example, and the whole installation process should follow the following three-part structure: 

Pre-installation inspection for Ground Source Heat Pumps

Your chosen installation contractor should first attend your home to complete an initial inspection, predominantly ensuring you know all the facts, and that your home is suitable for a ground source heat pump. They’ll look at whether a horizontal or vertical system would need to be the way forward, the geology of the land you’re looking to utilise, the existing insulation at your home, and whether the radiators and underfloor heating would need an upgrade too. 

Once this initial assessment has taken place, your engineer should be able to recommend the best ground source heat pump for your circumstances, tailoring their plan to ensure you get the most efficient system. It’s at this point they’ll be able to give you a price too. 

Ground Source Heat Pump Installation

Ground source heat pump installation can be a little more disruptive and invasive than the air source variety, and will add extra days to the install time. This is due to the excavation, whether it’s a borehole for a vertical system, or trench digging for a horizontal one. 

The pipes will then be installed and filled with TTF, before the engineers move on to adapting the ducting. It’s at this point that any internal heating upgrades should take place too, such as installing new underfloor heating, or larger radiators. 

The ductwork, ground loop and heating system will then be connected up to the pump, and tested for functionality. 

Post-installation and maintenance for Ground Source Heat Pumps

Your engineer should run through how your new ground source heat pump operates, and what you can expect from it going forward. They’ll also go over the ways you can optimise output on both heating and cooling settings throughout the season. 

An annual check is generally recommended for ground source heat pumps, although they’ll rarely need any attention outside of this. 

What are the advantages of a ground source heat pump? 

It uses a renewable energy source

Although it uses electricity to operate, the heat itself is generated for a ground source heat pump naturally beneath the earth, which isn’t exactly about to run out like oil or gas. 

It’s energy efficient

The Coefficient of Performance (COP) of a ground source heat pump produces more heat energy than it consumes, which gets you well on your way to saving money on your energy bills. Ground source heat pumps are generally around 400% efficient, which means that on average, your ground source heat pump produces four units of energy for every unit of electricity it uses. 

Ground source pumps can both heat and cool your home 

Global warming is quite literal, and, as we mentioned earlier, UK summers are hotting up. Therefore, a system to draw heat out of your home and therefore cool it down would be very handy indeed, which is good news if you get a ground source heat pump installed – this is exactly what it can do! 

They’re eligible for the Boiler Upgrade Scheme 

As we referred to earlier, the UK Government has incentivised the upgrade of heating systems within homes, and ground source heat pumps are eligible for a contribution too, just like their air source cousins. See the UK Government Boiler Upgrade Scheme website for more details. 

They’re low maintenance

A ground source heat pump is composed of few moving parts, so there’s less to go wrong. However, we’d still recommend an annual ‘service’ conducted by an MCS-accredited contractor, to make sure things are working efficiently. 

They last a long time

A properly maintained, modern ground source heat pump can last anywhere between 20-25 years. When you consider thatthe average lifespan of a gas boiler is between 10-15 years, a ground source heat pump becomes even better for your purse, and your peace of mind.

They’re quiet

Unlike air source heat pumps, ground source varieties are pretty much silent. 

What are the disadvantages of a ground source heat pump?

They’re expensive 

There’s no getting away from it; a ground source heat pump is a major investment for your home. While this investment pays off by letting you enjoy lower energy bills, there will be a big initial outlay that you’ll need to budget for if you want to get a heat pump installed. 

Their efficiency is affected by soil type 

This is a where-you-live kind of lottery, as soil type can affect the efficiency of your ground source heat pump. For example, sandy soil can reduce efficiency.

They’re not easily retrofitted

While it is possible, it’s much easier to plan and install a ground source heat pump as part of a new build project as opposed to in a house, which makes sense, as so much of it depends on ground work. 

They’re still dependent on electricity 

Just like air source heat pumps, ground source heat pumps use electricity to operate, so unless you’re generating that in a renewable way too (like solar, for example), you’ll still be relying on grid electricity.

You may need to upgrade your heating system

Because ground source heat pumps have a lower heat supply than fossil fuel-powered systems, the surface area they need to emit heat from needs to be larger, so you may need to invest in an underfloor heating system, or bigger radiators. 

Your home needs to be well insulated to start with

Any heating system will heat your home far less efficiently if your house isn’t well insulated – the ground source heat pump is no exception. 

What to consider when you’re thinking about getting an ground source heat pump 

How suitable your home is 

  • Those in flats won’t be able to benefit from a ground source heat pump on an individual basis
  • Assuming you’re in a house or bungalow, is there enough room for a ground source heat pump?
  • Is your home well insulated? A home with bad insulation won’t keep heat in regardless of whether it’s from a ground source heat pump or not.

Funding 

  • To ensure your heat pump works efficiently, will you need to upgrade your home’s heating system, such as installing underfloor heating or buying bigger radiators?
  • Would you be eligible for Government grants to contribute to the cost?

Installation 

  • Are you prepared for the disruption of installation, particularly the excavation required?
  • Are you able to find a Microgeneration Certification Scheme certified installer?

Should you get permission to install a heat pump?

Whilst you don’t generally need to get planning permission for either air or ground source heat pumps, there are a couple of big caveats, as well as some smaller ones. The first major one is that you should always double check with your local authority anyway, just in case. The second is that your heat pump should meet MCS standards

The other caveats are more building specific, such as rules around size and placement of external units, and restrictions if you live in a listed building or in a conservation area. It’s best to consult a full list of these rules before going ahead.  

Can you get grants for the installation of heat pumps? 

Yes – the good news is that the UK Government offers heat pump grants, which see them contribute up to £7,500 to the cost of installing a heat pump to replace your gas, oil or electric boiler system. This scheme, known as the Boiler Upgrade Scheme, runs until 2025, and helps homeowners cover the cost of a heat pump; as a heads up, it’s still likely that even the top amount of £7,500 won’t cover the entire cost of the pump and the install. 

Who is eligible for the Boiler Upgrade Scheme grant? 

You’ll be eligible for the Boiler Upgrade Scheme if:

  • You own the property – that includes second homes and buy-to-let properties
  • You’re replacing a system powered by fossil fuels
  • Your property is in England or Wales
  • You have a valid Energy Performance Certificate (EPC) with no outstanding recommendation for the property’s loft or cavity wall insulation – although there are some exemptions

How do I apply for a Boiler Upgrade Scheme grant? 

To make it infinitely less complicated for the homeowner, the MCS certified installer will apply for the grant on your behalf, and simply deduct the amount granted from the final amount. 

How can I pursue a Boiler Upgrade Scheme grant?

First, engage with an MCS accredited installer, like us here at Hartswood Heating. They’ll be able to advise you on whether the installation you’re after is eligible for the Government contribution. 

Once the installation has been agreed on and the grant applied for by the installer, you’ll need to respond to an email from Ofgem confirming that the installer is operating on your behalf. The installer will then have a set time frame, typically three months, within which to install the pump.  

How should you choose the right heat pump installer? 

Your heat pump is going to be in your house for a long time, and you’ll be relying on it, particularly in the winter months, so you want to make sure it’s installed properly so that it’s as efficient as possible. Engaging an MCS accredited heat pump installer is a non negotiable, but we’d also recommend the following in your search too: 

  • Check the MCS accreditation – the MCS have a list of accredited contractors on their website, so you can cross reference
  • Look for reviews of their work
  • Seek evidence of their previous heat pump installations

Choose Hartswood Heating for your heat pump installation 

It’s probably safe to say now that we know everything there is to know about heat pumps – we are an MCS accredited installer after all! Our friendly, knowledgeable team will be only too happy to talk you through individual questions and concerns, advising whether an air or ground source heat pump would suit your situation best, and make sure you have all the facts when you’re deciding which heat pump to go for. 

It’s our pleasure to make the introduction of renewable energy into homes as smooth as possible, so that you can look forward to lower energy bills, an efficient heating system, and peace of mind in knowing that everything is installed properly.