How Much Can You Really Save? A Detailed Analysis of Heat Pump Running Costs vs Gas Boilers
Introduction: The Question Every UK Homeowner Is Asking
With energy prices still elevated by historical standards and the government's Boiler Upgrade Scheme offering up to £7,500 towards a heat pump installation, the question of running costs has never been more pressing.
Yet the answer is rarely straightforward.
Heat pump running costs depend on a cascade of variables — your home's insulation, the efficiency of the heat pump itself, how you control it, and the tariff you're on.
Gas boilers have their own cost profile, and comparing the two requires moving past marketing language into hard numbers.
This article cuts through the noise.
Using publicly available Ofgem data, Energy Saving Trust figures, and real-world installation case studies from across the UK, it provides a practical framework for understanding what a heat pump will actually cost to run compared with a modern condensing gas boiler.
The goal is not to sell you on either technology but to give you the analytical tools to make a decision grounded in your specific property and circumstances.
Understanding How Heat Pump Efficiency Is Measured
Before comparing costs, you need to understand the metric at the heart of heat pump economics: the Coefficient of Performance (CoP).
This tells you how much heat a heat pump produces for every unit of electricity it consumes.
A CoP of 3.0 means 3 kWh of heat from 1 kWh of electricity.
Modern air source heat pumps regularly achieve CoPs between 2.5 and 4.0 depending on conditions.
The related metric used on product labels is the Seasonal Coefficient of Performance (SCoP), which averages performance across an entire heating season, accounting for temperature variation.
This is the figure you should look for when comparing models, not a single-point CoP quoted at a favourable external temperature.
Key data: The Energy Saving Trust estimates that a typical heat pump achieves a SCoP of around 2.5 to 3.0 in a reasonably insulated UK home.
This means for every £1 of electricity consumed, you receive £2.50 to £3.00 worth of heat energy.
By contrast, a modern condensing gas boiler converts around 90–94% of the energy in gas into usable heat.
The critical difference is that gas is priced in kilowatt-hours at a lower per-unit cost than electricity in the UK — at least for now.
This is where the comparison becomes nuanced.
The Current UK Energy Price Context
As of 2025, the UK Energy Price Cap (set by Ofgem) sits at approximately 24.5 pence per kWh for electricity and 6.8 pence per kWh for gas, based on a typical dual-fuel household consuming 12,000 kWh of gas and 2,900 kWh of electricity annually.
These figures are averages and vary by region and tariff.
The cap is revised quarterly, meaning these numbers will shift.
The fundamental problem for heat pump economics is the electricity-to-gas price ratio.
Electricity costs roughly 3.6 times more per kWh than gas under the current price cap.
This spread is the reason a heat pump needs to achieve a SCoP of at least 3.6 just to match gas on a like-for-like energy cost basis — before accounting for system inefficiencies, standing charges, and the cost of maintaining two heating systems.
Modelling Realistic Running Costs: A UK Semi-Detached Case Study
Let's work with a concrete example.
Consider a mid-terrace or semi-detached house in Bristol with three bedrooms, built in the 1960s, heated by an older combi gas boiler.
The property has cavity wall insulation and 100mm loft insulation — adequate but not optimal.
Annual gas consumption for heating and hot water is approximately 12,000 kWh.
The Gas Boiler Baseline
A modern condensing combi boiler like a Worcester Bosch Greenstar 30i will achieve around 94% efficiency under normal operation.
After accounting for standby losses and cycling inefficiencies common in real-world use, an effective efficiency of around 88–90% is more realistic.
- Heat required: 12,000 kWh
- Effective efficiency: 89%
- Gas consumed: 12,000 ÷ 0.89 = 13,483 kWh
- At 6.8 p/kWh: approximately £917 per year
Annual gas cost calculation:
This figure covers space heating and hot water.
It does not include standing charges or the boiler's annual service cost, typically £80–120 for a gas boiler.
The Air Source Heat Pump Scenario
Replacing the gas boiler with a Grant Aerona R32 air source heat pump (10kW model), the same property would require approximately 4,200 kWh of electricity annually to deliver the same heat output, assuming a SCoP of 2.86.
- Heat required: 12,000 kWh
- SCoP: 2.86
- Electricity consumed: 12,000 ÷ 2.86 = 4,196 kWh
- At 24.5 p/kWh: approximately £1,028 per year
Annual heat pump cost calculation:
At face value, this suggests the heat pump costs around £110 more per year to run.
But this comparison ignores several important factors that materially alter the real-world outcome.
The Variables That Change Everything
Insulation and Fabric Efficiency
A heat pump operates most efficiently when delivering low-temperature heat over extended periods — essentially mimicking how a well-insulated home naturally loses heat slowly.
In a poorly insulated property, a heat pump may struggle to maintain comfort levels in winter, leading to increased electricity consumption or supplementary heating.
The Energy Saving Trust estimates that improving a home's fabric efficiency from EPC band D to C can reduce heat pump running costs by 20–30%.
Key data: A solid-wall insulated property (EPC band C) typically requires 30–50% less heat than the same uninsulated property (EPC band E).
This reduction applies regardless of heating system, but it disproportionately benefits heat pump economics because you are paying for every kWh of electricity.
Heat Pump Tariffs and Off-Peak Electricity
One of the most significant levers available to heat pump owners is switching to an electricity tariff designed for heat pumps or electric heating.
Several UK energy suppliers, including Octopus Energy, E.ON, and OVO, offer time-of-use tariffs where overnight electricity costs as little as 7–9 p/kWh.
Running a heat pump's thermal store charging cycle during a 4-hour off-peak window can dramatically reduce electricity costs.
Pro Tip: If you have a hot water cylinder with a heating element (standard with most heat pump installations), set the timer to heat water during the cheapest off-peak period — typically between 00:30 and 04:30 on Agile Octopus or similar tariffs.
This single adjustment can reduce your hot water electricity cost by 40–60% compared with standard rate electricity.
Most unvented hot water cylinders used with heat pumps have a dedicated off-peak heating element precisely for this purpose.
The Impact of Flow Temperature
Gas boilers typically deliver heat through radiators at flow temperatures of 60–75°C.
Heat pumps work more efficiently at lower flow temperatures, ideally 40–55°C for underfloor heating or 45–55°C for properly sized radiators.
If your existing radiator system was designed for gas boiler flow temperatures and you install a heat pump without upsizing the radiators, the system may need to run at higher temperatures, reducing the CoP.
"We sized our radiator circuits for a 55°C flow temperature rather than the traditional 70°C.
It meant buying larger radiators for three rooms, but it means the heat pump runs at peak efficiency all winter." — Case study homeowner, Edinburgh, from the Clean Energy Installer database.
Ground Source vs Air Source: A Cost Comparison
Air source heat pumps (ASHPs) are far more common in UK residential settings due to lower installation costs.
Ground source heat pumps (GSHPs) achieve higher and more stable CoPs (typically 3.5–4.5) because ground temperature remains relatively constant around 10–14°C year-round.
However, ground source installations require either a borehole or a buried loop field, adding £10,000–£20,000 to installation costs compared with air source.
Annual Running Cost Comparison Table
The following table presents estimated annual space heating and hot water costs for three property types, comparing a modern condensing gas boiler against an air source heat pump on a standard tariff and an optimised off-peak tariff.
Figures are based on 2025 Ofgem price cap rates.
| Property Type | Annual Heat Demand | Gas Boiler Cost | ASHP — Standard Tariff | ASHP — Off-Peak Tariff |
|---|---|---|---|---|
| Mid-terrace, 2-bed (EPC C) | 7,500 kWh | £572 | £642 | £382 |
| Semi-detached, 3-bed (EPC C) | 12,000 kWh | £917 | £1,028 | £612 |
| Detached, 4-bed (EPC C) | 18,500 kWh | £1,414 | £1,585 | £944 |
| Semi-detached, 3-bed (EPC E) | 18,000 kWh | £1,375 | £1,542 | £918 |
These figures assume SCoP of 2.86 for the heat pump and 89% effective efficiency for the gas boiler.
Off-peak tariff calculated at 9.1 p/kWh for the off-peak period (the lower end of Agile Octopus rates in early 2025).
Hot water heating accounts for approximately 20% of total heat demand in all scenarios.
Key data: On an off-peak tariff, the heat pump becomes cheaper to run than gas in every property type in this analysis — saving between £190 and £470 annually compared with gas boiler heating costs.
The saving is most pronounced in larger, less efficient properties where electricity consumption is highest.
The Full Financial Picture: Installation Costs and Payback
Running costs tell only part of the story.
The Boiler Upgrade Scheme (BUS), which provides £7,500 for air source heat pump installations and £7,500 for ground source heat pumps (as of the current scheme round), substantially changes the economics.
Without the grant, installation costs for an air source heat pump typically range from £10,000 to £14,000, including the unit, cylinder, labour, and miscellaneous components.
With the BUS grant deducted, your net installation cost is closer to £2,500–£6,500.
Against the annual running cost saving of £190–£470 on an off-peak tariff, the payback period on the additional investment compared with a like-for-like gas boiler replacement is approximately 6–15 years — before factoring in the value of reduced maintenance costs, the projected rise in gas prices relative to electricity, or the potential uplift in property value from an EPC improvement.
Pro Tip: When comparing costs, do not compare a heat pump installation against a free boiler (which many homeowners receive as standard under warranty replacement).
Compare it against the full installed cost of a new gas boiler, which typically runs £2,500–£4,500 including a power flush, new thermostat wiring, and a 10-year warranty.
Your heat pump installation cost after BUS grant should be weighed against this net gas boiler investment figure, not against zero.
Maintenance and System Longevity
Gas boilers typically require annual servicing at £80–£120 and have a replacement cycle of 10–15 years.
Heat pumps require less frequent combustion system maintenance (there is no combustion) but benefit from periodic checks of refrigerant levels, filter cleaning (typically twice yearly), and inspection of the outdoor coil.
Annual heat pump maintenance costs from a qualified installer typically run £100–£150.
The components of a well-installed heat pump generally have longer operational lifespans than gas boilers — 20–25 years for the heat pump unit itself is a reasonable expectation, compared with 12–15 years for a gas boiler.
This extended lifespan partially offsets the higher upfront cost.
The Grant Landscape and What Changes Are Coming
The Boiler Upgrade Scheme has been oversubscribed in recent application windows, and the future of the grant level beyond the current spending review period remains uncertain.
The government has signalled its intention to end the installation of fossil fuel boilers in new-build homes from 2025 and has consulted on ending the installation of gas boilers in existing homes by 2035, though the detail of any mandate remains subject to policy development.
For homeowners considering the transition, the current availability of a £7,500 grant represents a meaningful subsidy that is unlikely to be permanently maintained at this level.
The strategic case for acting sooner rather than later rests not on the urgency of a deadline but on the window of maximum financial support.
Making the Decision: A Practical Framework
Heat pump running costs versus gas boiler costs cannot be reduced to a single number.
The practical framework below summarises the key questions you should answer for your own property:
- What is your property's current EPC rating, and what insulation improvements are recommended?
- Are you planning to install or already have underfloor heating or oversized radiators?
- Are you able to switch to an off-peak electricity tariff, and do you have a smart meter?
- What is the remaining lifespan of your current gas boiler?
- Do you qualify for the Boiler Upgrade Scheme, and is the grant currently available in your area?
- Are you in a rural area with no mains gas connection, where heat pump economics are typically more favourable?
- What is the installed cost of a new gas boiler vs a heat pump after grant in your circumstances?
Decision Framework Checklist:
For a well-insulated home (EPC band C or above) in an area with off-peak electricity tariffs available, the evidence suggests that a heat pump will be cheaper to run than a gas boiler within the current price environment.
For a poorly insulated property on a standard electricity tariff, gas remains the more economical choice — though improving insulation first and then reconsidering the heat pump option is likely to be the financially optimal path.
The comparison also depends heavily on how you value risk.
Gas prices are exposed to global commodity market volatility and are currently subsidised through the Energy Price Guarantee mechanism in ways that may not persist.
Electricity prices, while also volatile, are increasingly influenced by the falling cost of renewable generation, suggesting a longer-term trend of narrowing price ratios.
Conclusion: Informed Decision-Making Over Simple Answers
There is no universal answer to whether a heat pump is cheaper to run than a gas boiler in the UK.
The honest answer is: it depends on your insulation, your tariff, your system design, and your property type.
For many UK homeowners — particularly those in well-insulated homes who can access off-peak electricity rates — a heat pump now offers comparable or superior running costs to gas, combined with a significantly lower carbon footprint and access to a substantial government grant.
For others, particularly those in older, less insulated properties on standard tariffs, the transition requires more care.
The most financially prudent approach for most homeowners is to improve fabric efficiency first, then reassess heat pump economics, rather than treating the heating system replacement as a standalone decision.
The analysis in this article is based on publicly available data and reasonable modelling assumptions.
Energy costs fluctuate, grant availability changes, and individual properties vary.
Use this as a framework for your own research rather than a definitive prediction of your actual running costs, and consult a Microgeneration Certification Scheme (MCS) installer for a detailed heat loss calculation specific to your property before committing to either technology.