A heat pump allows you to heat your home by drawing heat from the surrounding environment instead of burning fuel.This cuts energy bills and reduces carbon emissions, but how much it does this depends on the efficiency of the heat pump you have.
But how do you measure and compare heat pump efficiency? Find out here, plus everything else you need to know about heat pumps, including installation, running costs and potential grants available.
Types of Heat Pumps
There are three main types of heat pumps: air source, ground source, and water source.
Air source heat pumps
(ASHP) can be air-to-water or air-to air. When people talk about air source heat pumps, they’re usually referring to the more common air-to-water heat pump.
Ground source heat pumps and water source heat pumps
Also known as geothermal pumps – achieve higher efficiencies than air source heat pumps.
The cost of installing a heat pump depends on the type you need for the size of your home, plus you may have the additional cost of upgrading your heating system.
How Do Heat Pumps Work?
Heat pumps use refrigeration technology, much like an air conditioner, but they can reverse the cooling process to create heat instead. Heat pumps provide home heating by drawing thermal energy from the air or ground around the property or from a nearby body of water.
The temperature of this heat is increased to run water-based or warm-air central heating. Most heat pumps also provide a domestic hot water supply.
In hot weather, heat pumps keep homes cooler by transferring heat outside.
Heat pumps are suitable for homes of all types and sizes, and hundreds of thousands have been installed across the UK so far. They work best in properties that are well insulated and have underfloor heating or large radiators. In most cases, planning permission isn’t needed to install a heat pump.
Heat Pump Sizes and Efficiency
The size of a heat pump doesn’t refer to its physical dimensions. Heat pump sizes are measured by how much heat energy they generate in kilowatts (kW) – units of a thousand watts. This is usually in the range of 6kW to 15kW.
Coefficient of Performance
Coefficient of performance (CoP) is the amount of power input of a heat pump compared with heating output. The higher the CoP, the more efficient the heat pump.
If a heat pump uses 10kW of electricity and produces 30kW of thermal energy, its CoP is 3. In other words, it produces three times more heat energy as the electrical energy it consumes. Put another way, we can say it’s 300% efficient.
An ideal heat pump CoP is generally 3 to 5.
Seasonal Coefficient of Performance
Coefficient of performance is a snapshot of heat pump efficiency at a given moment. Annual level of efficiency is calculated by taking into account seasonal performance. This gives us a seasonal coefficient of performance (SCoP).
CoP differs through the seasons because heat pumps need to work harder when outside temperatures fall. This makes them less efficient as they need more electrical energy to produce the same heat output.
SCoP calculates average heat pump efficiency as a ratio of total annual heat output per year compared with total electricity consumption.
Heat Pump Efficiency Levels
Heat pumps are highly efficient because they transfer heat instead of burning a fossil fuel.
You can expect your heat pump to be at least three times as efficient as a gas boiler. This is because the average efficiency level of heat pumps is around 300% – for every 1 unit of electricity used you could expect 3 units of heat energy to be generated. The best heat pumps can reach higher efficiency rates.
Heat pump efficiency is in part related to the type of heat pump installed. With each of the heat pump types you might expect the following average efficiency levels:
- Air source: 300%
- Ground source: 350%-450%
- Water source: 450%+
Heat Pump Running Costs
Running a heat pump costs on average about £1,540 a year, depending on the type of heat pump and factors such as:
- How much heat your home needs.
- Your preferred room temperature.
- Your electricity tariff.
- How efficient your heat pump is.
- Average air, ground or water temperatures around your property.
Air-to-Water Heat Pumps
The most common type of heat pumps in the UK, air-to-water heat pumps are becoming increasingly popular as a low-carbon, cost-effective way to heat our homes and provide hot water for taps.
The ideal central heating system for an air-to-water heat pump is underfloor heating but larger radiators can also work. If you don’t have a hot water cylinder, you’ll need to install one alongside your heat pump in order to get a hot water supply.
An air-to-water heat pump with cooling capabilities can also keep your home at a comfortable temperature in hot weather, while maintaining your hot water supply.
Air-to-water heat pumps require minimal maintenance and last 20 to 25 years. They use a small amount of electricity, reducing heating bills by up to 40%.
Although they average 300% energy efficiency, they can reach 500%.
Air-to-Water Heat Pump Costs
Air-to-water heat pump costs vary according to the size of the home and its heating and cooling requirements.
Estimated pricing is as follows.
- One-bedroom home – £8,400 to £11,150.
- Two to three bedrooms – up to £12,000
- Four to five bedrooms – £12,000-plus.
Air-to-Water Heat Pump Running Costs
Estimated annual running costs of an air-to air-water heat pumps are:
- £816 for a one-bedroom home.
- £1,130 for a two- to three-bedroom home.
- £1,790 for a home with four or more bedrooms.
Air-to-Air Heat Pumps
Instead of feeding a water-based central heating system, air-to-air heat pumps circulate warm air through rooms with blowers called fan coil units. An air-to-air heat pump can also work like air conditioning and maintain a comfortable, cooler temperature during spells of hot weather.
Unlike an air-to-water heat pump, an air-to-air heat pump doesn’t heat water. You’ll need a separate system to run your hot water supply to kitchens and bathrooms.
Air-to-air heat pumps are highly efficient in both warmer and colder areas. They last 10 to 15 years, reducing the amount of electricity needed to provide home heating and cooling.
Air-to-Air Heat Pump Costs
Air-to-air heat pumps are one of the most affordable types of heat pumps. Estimated pricing, excluding installation, is as follows.
- One-bedroom home – £2,400.
- Two-bedroom home – £4,000.
- Three-bedroom home – £6,500.
- Four bedrooms or more – £8,800.
On top of this is the cost of installation, which can range anywhere from £350 to £1,700 depending on the complexity of the job.
Air-to-Air Heat Pump Running Costs
Annual running costs for an air-to-air heat pump are around:
- £970 for a one-bedroom home.
- £1,200 for a two-bedroom home.
- £1,940 for a three-bedroom home.
- £2,590 for a four-plus bedroom home.
Ground Source Heat Pumps
Ground source heat pumps (GSHP) provide central heating and hot water by using heat from the ground around your home if there’s enough space to dig trenches or drill a borehole. They last longer than an air source heat pump, need less maintenance, and usually operate more quietly.
Ground source heat pumps also provide more reliable, consistent heat, achieving high levels of energy efficiency throughout the changing seasons.
They can achieve 450% energy efficiency all year round, peaking at up to 500%.
A ground source heat pump can also cool homes in hot weather. It does this with active cooling – reversing the heat pump refrigeration process – or by passive cooling uses cool water in the ground.
Ground Source Heat Pump Costs
Drilling a borehole for a ground source heat pump (vertical installation) is more expensive than digging trenches (horizontal installation).
Average costs are around:
- £16,000 to £30,000 for a horizontal ground source heat pump system.
- £23,000 to £50,000 for a vertical system.
Ground source heat pumps cost less to run than most other heating systems – from around £1,000 to £1,650 a year.
Water Source Heat Pumps
Water source heat pumps (WSHP) extract heat from a body of water such as a river, stream, pond or lake, water under the ground in aquifers, or from the sea. Like other types of heat pumps, water source heat pumps can cool homes as well as heat them.
Water source heat pumps are more efficient than both ground source and air source systems, reaching up to 600% energy efficiency. This is because heat flows better through water, and external water temperatures in the UK are stable all year, at up to 12C.
Water source heat pumps last 15-50 years. Specific environmental considerations apply to water source heat pumps and you may need a licence to install one.
Water Source Heat Pump Costs
It costs around £6,000 to £11,000 to install a water source heat pump. Those using refrigerant fluid are at the lower end of the price scale and need less maintenance.
Running costs and savings on energy bills depend mainly on the efficiency rating of the heat pump and the water source.
What Are Hybrid Heat Pumps?
Hybrid heat pumps combine a heat pump with another heat source, typically a gas, oil, or liquefied petroleum gas (LPG) boiler.
The system monitors outdoor temperatures and switches to the most energy-efficient option to keep your home warm and heat water. Efficiency levels are around 400%.
Hybrid heat pumps often provide a lower-carbon heating system when installing a regular heat pump isn’t practical. In other cases, a heat pump on its own might be unable to produce enough heat and hot water for larger properties.
While a hybrid heat pump may cost more than a gas boiler, it’s far less expensive than a standard heat pump. A quality hybrid heat pump can last 20 to 30 years.
Heat Pumps Vs Boilers
Boilers need to burn fuel to produce heat. This is why the government is phasing them out in the move towards net zero.
Heat pumps take advantage of thermal energy from a natural, external source that’s renewable.
Replacing an old G-rated gas boiler with a heat pump can save £340 a year on energy bills, according to the Energy Saving Trust.
Heat pumps use a limited amount of electricity. Seventy-five percent of the energy they consume is produced by the surrounding environment.
While boilers contribute to climate change, heat pumps reduce carbon emissions.
Heat pumps last longer than boilers and require less maintenance.
Role of Heat Pump Efficiency in Net Zero
The high efficiency of heat pumps plays a key role in decarbonising heating. Most of the energy they use is renewable.
Only a quarter of the energy needed by heat pumps is electricity. The rest is renewable energy provided by air, the ground, or water. This makes heat pumps more energy efficient than gas or conventional electric heating.
Although electricity costs more than gas, more of it is being produced by renewable sources such as solar, wind, and hydro.
When we burn fossil fuels – coal, oil, and natural gas – carbon dioxide and other greenhouse gases become trapped in the atmosphere. This drives climate change and global warming.
Less reliance on fossil fuels in favour of greener, cleaner electricity is seen as a major step in reducing carbon emissions and reaching net zero by 2025.
Heat pumps, which reduce carbon footprint by up to 44%, are a pivotal technology in achieving net zero emissions from residential heating. That’s why the government has set a target of 600,000 heat pump installations a year by 2028.
After 2035, gas boilers will no longer be allowed in new-build homes. A greener alternative heating system such as a heat pump will have to be installed.
Renewable Energy Financial Incentives
To help reach the net zero goal, the government has introduced a range of heat pump grants that cut installation costs considerably. Plus VAT has been scrapped on heat pumps until March 31, 2027, provided they’re supplied and installed by the same company. It will then go back to the reduced rate of 5%.
Heat Pump Grants
Various government-backed grants are available to householders who want to install a heat pump. These cover a large part of the cost or you may be able to get a heat pump for free, until the money runs out. The government has allocated a specific amount of heat pump funding, so it works on a first come, first served basis.
Heat pump funding schemes are open to homeowners and private sector landlords for the next few years. What happens then remains unclear.
Meanwhile, eligibility conditions for some grants have been relaxed, making it easier and more affordable to install a heat pump.
The most widely available heat pump grants come from the Boiler Upgrade Scheme, which is open to all households. Other funding is available via energy suppliers and local councils, but you may need to be getting a state benefit.
Boiler Upgrade Scheme
The £450 million Boiler Upgrade Scheme (BUS) provides grants of £7,500 for households who want to replace old energy-inefficient heating with an air source, ground source or water source heat pump.
The initiative, which runs in England and Wales, was launched in 2022 and is scheduled to close at the end of March 2028.
The government has now ended the home insulation requirements of BUS eligibility. From May 2024, funding is available without having to spend a few thousand pounds installing loft or cavity wall insulation.
ECO4 Funding
The fourth and final phase of the Energy Company Obligation – ECO4 – focuses on the least energy-efficient homes and households in fuel poverty in England, Scotland and Wales.
Households on a means-tested benefits may qualify for a free or partially-funded heat pump if they have an Energy Performance Certificate (EPC) rating of D to G.
ECO4 funding will continue until April 2026 if the £4 billion available doesn’t run out sooner as energy providers meet their funding obligations.
ECO4 Flex
Local Authority Flexible Eligibility widens the scope of the Energy Company Obligation. With ECO4 Flex – also known as LA Flex – low-income households not claiming benefits can get a heat pump grant. Local councils set their own funding criteria for families and individuals living in fuel poverty.
Other Heat Pump Grants
Some other heat pump grants for households on low income include:
- The Home Upgrade Grant (HUG) in England.
- Warmer Homes Scotland.
- Nest scheme in Wales.
- The Sustainable Community Buildings initiative in Northern Ireland.