Air source heat pumps vs ground source heat pumps vs boilers: which is right for you?
16 December 2021 | Aimee Tweedale
Is your heating system getting slow and unreliable in its old age? Are you facing boiler breakdowns this winter? Sounds like it’s time to think about a new central heating system. But which one to choose?
There’s a lot of talk in the media right now about heat pumps. These electric, low-carbon alternatives to boilers offer a modern way to heat your home without using natural gas or oil (which are fossil fuels).
If you do decide to get a heat pump installed, you might be wondering which type to go for. Air source heat pumps are a bit cheaper, while ground source heat pumps are more efficient, and better for bigger homes.
If you’re stuck trying to choose between an air source heat pump, ground source heat pump, or new boiler, we’ve got you covered. Here’s how they compare in terms of cost, efficiency, and installation.
The cost of buying heat pumps vs boilers
If the price tag is your biggest concern, then you should note that heat pumps have a higher upfront cost than boilers. This is because they’re still relatively new in the UK, and installing them is still a less common skill. But as the heat pump trade grows in the UK, prices are expected to fall.
As a rough guide, including parts and labour, these are the average prices at the moment:
- Air source heat pumps cost between £7,000 and £13,000 to install1
- Ground source heat pumps can be as much as £14,000 to £19,0002
- A new gas boiler usually costs between £2,000 and £4,0003
If you’re weighing up the cost of getting an air source heat pump vs a gas boiler, it’s easy to see that you’ll be paying less upfront for a boiler. But remember that heat pumps are very efficient, and if you’re replacing an old, inefficient oil or electric heating system, you could save money on your running costs.
Not to mention: the government’s Boiler Upgrade Scheme offers a grant of £5,000 for homeowners to install an air source heat pump (or £6,000 for ground source heat pumps). That’s worth factoring into your costs! The scheme will be available from early 2022, and you can read all about it here.
Remember, exactly how much your heat pump or boiler costs will depend on lots of factors, such as:
- The size of your home
- The make and model you choose
- Where in the country you live
- What kind of system you’re replacing
For the full rundown, read our comprehensive guide to how much it costs to get an air source or ground source heat pump.
The efficiency of heat pumps vs boilers
When it comes to efficiency, heat pumps are the clear winners.
How efficient your gas boiler is will depend on its rating and how old it is. Read our full guide to boiler efficiency to learn more about different boiler ratings and what they mean.
Boiler efficiency is often described in percentages. For example, you might hear of a boiler described as “90% efficient”. This means that 90% of its energy goes towards heating your home, while the other 10% is lost. The average modern boiler is around 85-95% efficient4.
The efficiency of heat pumps is usually expressed in the form of their Coefficient of Performance, or CoP. The CoP figure tells you how much heat the pump can generate for each unit of power it receives. A heat pump with a CoP of 3 can generate 3 units of heat per one unit of electricity. Air source heat pumps typically have a CoP of between 2.5 and 45.
If you want to compare that to a boiler’s efficiency, you can convert it into percentages. A CoP of 3 is the same as being 300% efficient!
If you’re considering an air source heat pump vs a ground source heat pump, the slightly more efficient choice is a ground source heat pump. This is because when it’s cold outside, air source heat pumps are more exposed to the drop in the temperature, so they have to use more energy to heat up your home. But ground source heat pumps have better insulation, because their pipework is buried underground.
The cost of running heat pumps vs boilers
Right now, the cost of electricity per kWh is higher than that of gas in the UK.
The average UK home uses around 12,000 kWh per year on heating. That amounts to an average heating bill of around £453.24 for a home with a gas boiler6. Read more about how to work out your yearly heating bill.
Heat pumps are powered by electricity, which is more expensive. But they’re also more efficient than gas boilers (see our section on efficiency, above). This means that they can make each kWh go further. So, if you had an air source heat pump that used 12,000 kWh per year at a unit rate of 17.2p (the UK average), and had a CoP of 3, you’d spend about £688 annually to power your heat pump.
How much you’ll spend on running costs exactly depends on lots of factors, like:
- The size of your home and the size of your heating system
- Your energy tariff
- The time of year (and the temperature outside!)
- Whether you’re getting the Renewable Heat Incentive
Whether or not a heat pump could save you money depends on what system you’re replacing. If you’re replacing an old, inefficient oil boiler, you could save on your running costs. But while electricity prices stay higher than gas, gas boilers are still likely to be the less expensive option.
Installing a heat pump vs installing a boiler
What about the process of actually getting your new heating system installed? Setting up any new heating system is a big job, but ground source heat pumps are among the trickiest and most time-consuming.
Here’s a quick overview of what it’s like to get a new boiler or heat pump installed.
Getting a new boiler installed
Most boiler installations are a relatively simple process. If you’re replacing a boiler like-for-like (for example, you’re getting a new combi boiler to replace your old combi), the whole job should be done within a day.
If you’re getting a different size or type of boiler, it could take a bit longer. A Gas Safe-registered engineer will come round to assess the job and will take care of it all, so you can just put your feet up and relax.
When the job’s done, they should give you a Building Regulations Certificate to prove that the boiler has been installed in accordance with legal guidelines.
Getting an air source heat pump installed
Finding an air source heat pump installer might take a bit longer or cost a bit more than a boiler engineer, because it’s still a fairly niche skill. You’ll need to find an installer who’s certified by the Microgeneration Certification Scheme.
Once you’ve got an installer, they’ll carry out an assessment of your home to plan the job.
Air source heat pumps can take a bit longer to install than boilers because there are a few different elements to the job. The pump itself will be installed on a flat concrete base outside. The engineers will also have to install a hot water tank inside your home, and in most cases they’ll replace the radiators, too.
In an average 3-bed house, it might take 3 engineers about 4-5 days to install an air source heat pump.
Getting a ground source heat pump installed
Ground source heat pump installation is the most involved process of the 3 options listed here. To begin the process, you’ll also need to find an installer certified by the Microgeneration Certification Scheme.
Installers will probably need to drill or dig holes into your garden to lay down the pipework, so expect to have diggers or other machinery in your garden.
How long it will take depends on your property, the installers, and lots of other factors. But in general, it takes at least a week7.
The lifespan of heat pumps vs boilers
This is an area where heat pumps are the clear winners.
How long does a heat pump last?
Well-maintained heat pumps can last as long as 20-30 years8. That could be as much as 25-50% longer than the lifespan of your gas boiler!
What does it mean to keep your heat pump well-maintained? The good news is that heat pumps don’t need a lot of attention. You should ideally have them serviced each year by a professional, to check that they’re working properly. Other than that, the main things you’ll need to look out for are:
- Cleaning filters, coils, and fans
- Keeping debris like leaves away from the pump
More good news: heat pumps don’t usually need expensive parts to be replaced during their lifetime.
How long does a boiler last?
Gas boilers usually last around 10 years, but can go as far as 15 if you really take care of them.
So: which heating system is right for you?
In the debate of ground source vs air source heat pumps, it all comes down to your personal circumstances. For most people, with smaller homes and gardens, an air source heat pump will be the more practical option.
But if you’ve got a big home to heat, and lots of garden space, a super-efficient ground source heat pump could keep you toasty for many years to come.
If you’re wondering about whether to go with a heat pump or gas-fired heating, we’d champion heat pumps. While the price tag means they’re not for everyone, if you can afford it, they’re an awesome carbon-kicking piece of technology.
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Sources and references
6 This is calculated on the basis of a home with a gas boiler. This uses the average annual space heating energy consumption of a UK household of 10301.31kWh, according to 2018 data from Odyssee here and converted into kWh. This is multiplied by the UK’s average unit gas price of 4.44 pence/kWh, as per Ofgem reporting here.