Heat pumps have been generating a lot of buzz in the UK over the past few years — and for good reason. With rising energy bills, government net-zero targets, and the planned phase-out of new gas boiler installations by 2035, many homeowners are asking whether a heat pump could be the right choice for their home. This guide cuts through the noise to give you a clear, balanced picture of what heat pumps are, how they work, what they cost, and whether your home is a good candidate.
How a Heat Pump Works
Despite the technical-sounding name, the principle behind a heat pump is surprisingly straightforward. Rather than burning fuel to generate heat, a heat pump moves heat from one place to another — much like a refrigerator in reverse.
Here’s the basic process:
- A refrigerant fluid absorbs heat energy from the outside air or ground (even at temperatures as low as -15°C)
- The refrigerant is compressed, which raises its temperature significantly
- That heat is then transferred into your home’s heating and hot water system
- The refrigerant expands and cools, ready to absorb more heat and repeat the cycle
Because the system is moving heat rather than creating it, it can deliver more energy than it consumes — which is what makes heat pumps so efficient.
Air Source vs Ground Source Heat Pumps
There are two main types of heat pump available to UK homeowners, each with its own advantages and installation requirements.
Air Source Heat Pumps (ASHPs)
Air source heat pumps extract heat from the outside air. They are by far the most common type installed in UK homes.
Pros:
- Lower installation cost (typically £7,000–£10,000 before grants)
- Suitable for most properties with outdoor space
- Relatively straightforward installation — usually one to two days
- Eligible for the Boiler Upgrade Scheme grant
Cons:
- Efficiency drops slightly in very cold weather
- The outdoor unit produces some noise (similar to an air conditioning unit)
- Requires a suitable outdoor location for the unit
Ground Source Heat Pumps (GSHPs)
Ground source heat pumps extract heat from the ground via buried pipes (a ground loop), which maintain a more stable temperature year-round.
Pros:
- More consistent efficiency throughout the year
- Quieter operation — no outdoor fan unit
- Slightly higher efficiency than air source in cold conditions
Cons:
- Higher installation cost (typically £15,000–£25,000)
- Requires significant garden space for horizontal ground loops, or deep boreholes for vertical systems
- More disruptive installation process
For most UK homeowners, an air source heat pump is the more practical and affordable starting point.
Efficiency: COP of 3–4 vs Gas Boilers
One of the most compelling arguments for heat pumps is their efficiency — but it helps to understand the numbers.
Coefficient of Performance (COP)
The Coefficient of Performance (COP) measures how much heat energy a system delivers for every unit of electrical energy it consumes. A heat pump with a COP of 3.5 delivers 3.5 kWh of heat for every 1 kWh of electricity used.
By comparison, even the most efficient condensing gas boiler has a COP of around 0.9 — meaning it converts 90% of the gas it burns into useful heat, with the rest lost as waste.
Seasonal COP (SCOP)
Because outdoor temperatures vary throughout the year, heat pump efficiency is also measured as a Seasonal Coefficient of Performance (SCOP), which averages performance across an entire heating season. A well-installed air source heat pump in the UK typically achieves an SCOP of 2.5–3.5.
The key caveat is that electricity currently costs more per unit than gas in the UK. However, the higher efficiency of a heat pump can offset this difference — particularly if you’re on a heat pump-friendly electricity tariff.
Is Your Home Suitable?
Heat pumps work best in well-insulated homes. This is arguably the most important factor to consider before investing.
Insulation
Because heat pumps operate at lower flow temperatures than gas boilers (typically 35–55°C rather than 60–80°C), your home needs to retain heat effectively. Key areas to address include:
- Loft insulation — at least 270mm of mineral wool is recommended
- Wall insulation — cavity wall insulation or external/internal wall insulation for solid walls
- Floor insulation — particularly important for ground floors
- Double or triple glazing — to minimise heat loss through windows
Radiators and Underfloor Heating
Because heat pumps deliver heat at lower temperatures, your existing radiators may need to be upsized to compensate. Underfloor heating is ideal for heat pump systems, as it operates efficiently at low flow temperatures and distributes heat evenly.
A good installer will carry out a full heat loss calculation for your home to determine whether your existing radiators are adequate or need upgrading.
Older vs Newer Homes
Modern, well-insulated homes (built to post-2000 standards or better) are generally well-suited to heat pumps. Older properties — particularly solid-walled Victorian or Edwardian homes — can still benefit, but may require more preparatory work on insulation and heat emitters. This doesn’t make them unsuitable, but it does affect the overall cost and complexity of the project.
Costs: What to Budget
Installed costs vary depending on the type of heat pump, the size of your home, and the amount of preparatory work required.
Air Source Heat Pumps
- Typical installed cost: £7,000–£10,000 (before the Boiler Upgrade Scheme grant)
- After the £7,500 grant: effectively £0–£2,500 for many homeowners
- Additional costs may include radiator upgrades, pipework modifications, and a new hot water cylinder
Ground Source Heat Pumps
- Typical installed cost: £15,000–£25,000 depending on ground loop type and home size
- After the £7,500 grant: £7,500–£17,500
- Borehole drilling adds significant cost but is necessary where garden space is limited
Additional Costs to Consider
- Hot water cylinder (if not already present): £500–£1,500
- Radiator upgrades: £150–£400 per radiator
- Electrical upgrades (if required): £500–£2,000
- Insulation improvements: variable, but often eligible for separate government schemes
The Boiler Upgrade Scheme
The Boiler Upgrade Scheme (BUS) is the UK government’s primary financial incentive for homeowners switching from fossil fuel heating to low-carbon alternatives.
What’s on Offer (2024/25)
- £7,500 grant for air source heat pumps
- £7,500 grant for ground source heat pumps
- The grant is paid directly to your MCS-certified installer, who deducts it from your invoice — you never handle the money yourself
Eligibility
To qualify for the Boiler Upgrade Scheme, you must:
- Own the property (landlords and social housing providers may also apply)
- Have a valid Energy Performance Certificate (EPC) with no outstanding recommendations for loft or cavity wall insulation
- Use an MCS-certified installer
- Be replacing a fossil fuel heating system (gas, oil, or LPG boiler)
How to Apply
You don’t apply directly — your MCS-certified installer handles the application on your behalf. The key steps are:
- Obtain an up-to-date EPC for your property
- Address any outstanding insulation recommendations noted on the EPC
- Get quotes from MCS-certified heat pump installers
- Your chosen installer submits the BUS application before installation begins
- The grant is deducted from your final invoice
Running Costs vs Gas
Understanding the running cost comparison between a heat pump and a gas boiler requires looking at both unit energy costs and system efficiency.
The Unit Cost Challenge
As of 2024/25, electricity costs roughly 24–28p per kWh under the Energy Price Cap, while gas costs around 6–7p per kWh. At first glance, this makes electricity look significantly more expensive.
How COP Changes the Picture
However, because a heat pump with a COP of 3 delivers three units of heat for every unit of electricity consumed, the effective cost per unit of heat is much closer to gas:
- Gas boiler (90% efficient): ~7p ÷ 0.9 = ~7.8p per kWh of heat
- Heat pump (COP 3.0): ~26p ÷ 3.0 = ~8.7p per kWh of heat
The gap narrows further with a higher COP or a cheaper electricity tariff. Several energy suppliers now offer heat pump-specific tariffs with lower overnight rates, which can significantly improve the economics.
Typical Annual Running Costs
For an average three-bedroom semi-detached home:
- Gas boiler: approximately £900–£1,200 per year
- Air source heat pump (standard tariff): approximately £1,000–£1,400 per year
- Air source heat pump (heat pump tariff): approximately £800–£1,100 per year
These figures vary considerably depending on home size, insulation quality, and usage patterns. A well-insulated home with a correctly sized heat pump and a good tariff can achieve running costs comparable to — or lower than — a gas boiler.
Pros and Cons
Pros
- High efficiency — COP of 3–4 means more heat per unit of energy than any fossil fuel system
- Lower carbon emissions — especially as the UK electricity grid becomes greener
- Government grant available — £7,500 off the installed cost via the Boiler Upgrade Scheme
- Long lifespan — heat pumps typically last 15–20 years with proper maintenance
- Provides cooling — some models can reverse the cycle to cool your home in summer
- Future-proof — aligned with the UK’s long-term decarbonisation strategy
- Consistent comfort — lower flow temperatures mean more even, gentle heat distribution
Cons
- Higher upfront cost — even after the grant, installation is a significant investment
- Electricity is currently more expensive than gas — running costs depend heavily on tariff and COP
- Not suitable for all homes without preparation — poor insulation or undersized radiators reduce performance
- Requires outdoor space — for the external unit (air source) or ground loop (ground source)
- Lower flow temperatures — may require radiator upgrades in older homes
- Planning permission — usually not required, but some listed buildings or conservation areas may have restrictions
Questions to Ask Your Installer
Before committing to a heat pump installation, make sure you get clear answers to these questions:
- Will you carry out a full heat loss calculation for my home? A proper MCS-compliant heat loss survey is essential for correct system sizing.
- Are my existing radiators adequate, or will they need upgrading? Ask for a room-by-room assessment.
- What SCOP do you expect this system to achieve in my home? A reputable installer should be able to give you a realistic efficiency estimate.
- Are you MCS-certified? This is a requirement for the Boiler Upgrade Scheme grant — always verify.
- What will my estimated annual running costs be? Ask for a written estimate based on your home’s heat loss and local energy tariffs.
- What does the warranty cover, and for how long? Most heat pumps come with a manufacturer’s warranty of 5–7 years; some installers offer extended cover.
- Will you handle the Boiler Upgrade Scheme application on my behalf? A good installer will manage this process for you.
Conclusion
Heat pumps are not a perfect solution for every home, but for many UK homeowners they represent a genuinely compelling option — particularly with the £7,500 Boiler Upgrade Scheme grant reducing the upfront cost. The technology is proven, the efficiency gains are real, and the long-term direction of travel is clear.
The most important steps are to ensure your home is well insulated, choose an MCS-certified installer who carries out a proper heat loss survey, and explore heat pump-specific electricity tariffs to keep running costs competitive. Done right, a heat pump can provide reliable, comfortable heating for 15–20 years while significantly reducing your home’s carbon footprint.
If you’re ready to explore your options, getting a quote from a qualified heating engineer is the natural next step.
