A heat pump’s running cost depends on two things: how efficiently it converts electricity into heat (its seasonal coefficient of performance, or SCOP), and how expensive electricity is relative to the fuel it is replacing. The relationship between these two factors determines whether switching to a heat pump saves money, costs more, or comes out roughly even on running costs. At current UK tariffs, the answer depends heavily on what fuel you are switching from and how well insulated your property is. This calculator takes your current fuel type, annual heating bill, property insulation level, and electricity tariff and shows the estimated heat pump running cost, the annual saving or additional cost versus your current system, and the financial case for installation including the Boiler Upgrade Scheme grant and any home improvement loan used to fund the work. All figures are illustrative. The information is general and does not constitute financial or energy advice.
For oil and LPG-heated properties, the comparison is typically favourable: the narrower gap between electricity and these fuel prices means a heat pump usually costs less to run, sometimes significantly so. For gas-heated properties, the outcome depends on the specific electricity-to-gas price ratio at the time, the SCOP the heat pump achieves, and whether the household uses a heat pump-specific time-of-use tariff. At some tariff levels, a well-installed heat pump in a well-insulated property can match or beat gas running costs; at others, there is an additional running cost that is offset by the capital saving from the Boiler Upgrade Scheme grant. The tool below shows this honestly for your inputs.
At a Glance
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The running cost outcome depends primarily on which fuel you are switching from and the electricity-to-gas price ratio at the time.
At current UK tariffs, a heat pump needs to achieve a SCOP roughly equal to the electricity-to-gas price ratio, adjusted for boiler efficiency, to match gas running costs. This breakeven SCOP changes every quarter as Ofgem resets the price cap. The calculator below lets you enter your actual fuel and electricity rates to see the position for your property. For oil and LPG, the price gap with electricity is much narrower, and a heat pump operating at SCOP 2.8 or above typically produces a genuine annual saving. The case for switching from gas depends on the tariff picture at the time of installation; from oil and LPG, the case is typically an immediate bill saving.
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Insulation quality is the single biggest factor in heat pump efficiency, and properties at EPC E or below should insulate before installing.
A heat pump’s SCOP depends on the flow temperature it needs to maintain: a well-insulated property runs at 35 to 45 degrees, a poorly insulated one at 55 to 65 degrees, with a significant efficiency penalty at the higher temperature. Installing in a poorly insulated property produces an oversized system that runs less efficiently and costs more to run. Insulating first and sizing the heat pump for the improved property produces the best operational and financial outcome.
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The Boiler Upgrade Scheme grant of £7,500 (or £9,000 for oil and LPG properties until March 2027) changes the capital comparison materially.
Heat pumps typically cost £8,000 to £15,000 installed, so the grant reduces the net capital cost to a level often comparable to a high-end boiler replacement. This reshapes the financial case independent of running cost saving. The BUS was overhauled in April 2026: the EPC requirement was removed, oil and LPG properties received a higher grant of £9,000 (valid 21 July 2026 to 31 March 2027), and the scheme was extended to 2030. An MCS-certified installer is required. Check current scheme status on GOV.UK before relying on it in a budget.
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Heat pump-specific time-of-use electricity tariffs can reduce running costs compared with a standard unit rate, and are worth modelling in the calculator.
Several suppliers offer tariffs designed for heat pump households, with off-peak windows at lower rates than the standard unit rate. Because heat pumps can run during off-peak periods to pre-heat the property and store warmth in the building fabric, households on these tariffs achieve lower effective electricity costs across the day. The size of the saving depends on the specific tariff, the proportion of consumption that falls in off-peak windows, and how well the property retains heat. To model this in the calculator, reduce the electricity rate slider to your expected blended average across the day rather than the standard unit rate.
Interactive tool
Heat pump running cost calculator
Enter your current fuel, annual bill, property insulation level, and electricity rate. See estimated heat pump running costs, the annual saving or additional cost versus your current system, and the financial case including BUS grant and loan financing.
Your data stays private — nothing you enter is stored, transmitted, or accessible to anyone. All calculations run entirely in your browser.
Your current heating system
Modern condensing gas boiler – assumed efficiency: 90%
Your property
Reasonably insulated property. A typical mid-range SCOP for a modern installation. Further insulation improvements would raise this.
Show the working
Installation cost and loan
About This Calculator
The SCOP figure
What the Seasonal Coefficient of Performance means
The SCOP is the ratio of heat delivered to electricity consumed across a full heating season. A SCOP of 3.0 means the heat pump delivers 3 units of heat for every 1 unit of electricity it uses. A higher SCOP means lower electricity consumption for the same heat output. The SCOP is primarily determined by how warm the heat pump needs to make the water circulating through the heating system: lower flow temperatures in a well-insulated property allow higher SCOP. Poorly insulated properties require higher flow temperatures, which reduces efficiency. The national average SCOP across monitored UK heat pump installations in the 2025–26 heating season was 3.4 (Energy Systems Catapult / MCS data), with well-installed systems in well-insulated properties achieving higher.
The gas comparison
How the gas-to-heat-pump running cost comparison works
The running cost comparison between gas and a heat pump depends on the electricity-to-gas price ratio and the SCOP. A heat pump needs to achieve a SCOP roughly equal to the price ratio (adjusted for gas boiler efficiency) to break even on running costs. This breakeven SCOP changes every quarter as Ofgem resets the cap: at some tariff levels it is achievable for well-insulated properties, at others it exceeds what most installations deliver. The calculator lets you enter your actual rates and see the position for your property. A heat pump-specific time-of-use tariff, which reduces the effective electricity rate, can close the gap significantly. The long-term direction also favours the heat pump as the grid decarbonises and the relative cost of gas rises.
Boiler Upgrade Scheme
What qualifies and how the grant works (updated April 2026)
The BUS provides £7,500 toward the installation of an air source or ground source heat pump, rising to £9,000 for oil and LPG off-grid properties (21 July 2026 to 31 March 2027). The grant is claimed by the MCS-certified installer and deducted from the invoice before the homeowner pays. The April 2026 overhaul removed the EPC requirement: a valid EPC is no longer needed to apply, and there is no requirement for outstanding insulation recommendations to be addressed first. The scheme has been extended to 31 March 2030 with a £400 million annual budget. Always check GOV.UK for current status, as the scheme can still close if funding is exhausted in-year. The toggle in the calculator above removes the grant from the calculation to show the position without it.
Heat pump tariffs
How the right electricity tariff changes the picture
Several suppliers now offer electricity tariffs designed for heat pump households, with off-peak windows at lower rates than the standard unit rate. Dedicated heat pump tariffs such as Cosy Octopus typically offer off-peak rates in the 10 to 15p/kWh range against a standard cap rate of around 26p. Because heat pumps can run during off-peak periods to pre-heat the property and store warmth in the building fabric, households on these tariffs can achieve lower effective electricity costs than the standard unit rate. This calculator uses a single unit rate for simplicity: if you have or intend to switch to a time-of-use tariff, reduce the electricity rate slider to reflect your expected blended average cost per kWh across the day.
Insulation and Heat Pumps: Why Order Matters
A heat pump’s efficiency is directly related to the flow temperature it needs to maintain: the warmer the water circulating through radiators or underfloor heating needs to be, the harder the heat pump works and the lower its SCOP. In a well-insulated property, a lower flow temperature of 35 to 45 degrees Celsius is sufficient to maintain comfort. In a poorly insulated property, 55 to 65 degrees may be needed, which significantly reduces efficiency and increases running costs.
The practical implication is that insulation improvements before heat pump installation increase the SCOP the system achieves in practice, reduce the size of heat pump needed (which reduces the capital cost), and improve the running cost comparison against the existing system. Installing a heat pump in a property that still needs insulation, then adding insulation later, typically produces a system that is oversized for the post-insulation heat demand and therefore runs less efficiently than it would if it had been specified for the insulated property from the start. Our home energy upgrade sequencer can help plan the order and timing of insulation and heat pump work. Our guide to home improvement loans for energy efficiency upgrades covers insulation options and funding in detail, and our guide to government grants vs home improvement loans covers which insulation measures may qualify for grant funding.
How to Use This Calculator
Select your current fuel and annual bill
Select the fuel your current heating system uses. For the annual bill, use your actual spend on space heating and hot water over the last twelve months, not your total energy bill. If you have a dual-fuel property with gas heating and a separate electricity meter for other uses, use the gas portion only. The fuel rate slider shows the current default for your fuel type: adjust it if you know your actual unit rate from a recent bill or tariff statement.
Select your EPC rating
Use your most recent EPC certificate. If you do not have one, an EPC is available on the government’s Find an Energy Certificate service using your address. Select the nearest band to your property’s current rating. The EPC determines the SCOP estimate, which drives the running cost calculation. Note that while the BUS no longer requires a valid EPC, knowing your insulation level is still essential for an accurate running cost estimate.
Enter your electricity rate and check the BUS toggle
Your current electricity unit rate is on your energy bill. If you are considering switching to a heat pump-specific tariff, use that tariff’s blended average rate rather than the standard unit rate to see how a time-of-use tariff affects the comparison. Toggle the BUS grant on or off to see the installation cost with and without it. The grant amount adjusts automatically for oil and LPG properties.
Set the system cost and loan terms
Use the quote from an MCS-certified installer if you have one. If not, £8,000 to £15,000 is a typical range for a domestic air source heat pump installation before the BUS grant. Adjust the APR and term to reflect the product you are considering or to test how different terms affect the break-even position.
Related Tools and Guides
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All of our home improvement loan guides and tools in one placeFrequently Asked Questions
My current system is gas. Does a heat pump make financial sense?
The answer depends on the electricity-to-gas price ratio at the time and the SCOP your property can achieve. A heat pump needs to achieve a SCOP roughly equal to the price ratio (adjusted for gas boiler efficiency of around 90%) to match gas running costs. This breakeven SCOP changes each quarter as Ofgem resets the price cap. At some tariff levels, a well-installed heat pump in a well-insulated property (SCOP 3.2 or above) matches or beats gas running costs; at others, there is an additional running cost. The calculator above shows the position at whatever fuel and electricity rates you enter, and the show-the-working section displays the breakeven SCOP for your inputs.
The financial case for switching from gas rests on several factors beyond running cost: the Boiler Upgrade Scheme grant of £7,500 reduces the capital cost significantly, making the installation cost comparison with a gas boiler replacement more competitive. Heat pump-specific time-of-use tariffs can reduce the effective electricity rate in households that shift consumption to off-peak periods. And as the electricity grid decarbonises through the 2030s, the relative cost of electricity versus gas is expected to narrow, improving the running cost comparison over time. If your gas boiler is approaching the end of its life and you are comparing heat pump installation against boiler replacement, the BUS grant changes the capital comparison materially and is the most important factor to confirm first.
What size heat pump does my property need?
Heat pump sizing is calculated from the property’s heat loss rate, which is determined by the floor area, insulation levels, number and type of windows, and the temperature difference between inside and outside on the coldest expected day. An MCS-certified installer is required to carry out a heat loss calculation before specifying a heat pump, and this should be the basis for the system size, not a rule of thumb based on property size alone. As a general guide, a typical three-bedroom semi-detached house in England with average insulation has a heat loss of approximately 6 to 9 kilowatts on a cold day, which typically requires a 7 to 10kW heat pump.
Oversizing is a common problem in heat pump installations, particularly when the calculation is done without improving insulation first. An oversized heat pump cycles on and off more frequently rather than running continuously at low output, which reduces its efficiency and increases wear. Getting the heat loss calculation right, and improving insulation before the calculation is done where possible, produces a system that is appropriately sized for the post-insulation property and runs more efficiently as a result.
Do I need to replace my radiators when installing a heat pump?
Not necessarily, but it depends on the size of your existing radiators and the flow temperature the heat pump needs to operate at. Gas boiler radiators are typically sized for flow temperatures of 60 to 80 degrees Celsius, depending on the age and type of the boiler. A heat pump operates most efficiently at flow temperatures of 35 to 50 degrees Celsius. At lower flow temperatures, smaller or older radiators may not produce enough heat output to maintain comfortable room temperatures. A heat loss calculation, which the installer is required to carry out, will identify which rooms need larger radiators and what the replacement or upgrade cost is.
In practice, many properties with reasonably modern radiators can operate a heat pump at higher flow temperatures of 50 to 55 degrees without replacing radiators, accepting a slight SCOP penalty. Others, particularly older properties with small or old radiators, need significant radiator upgrades before the system works well. The radiator upgrade cost is not covered by the BUS grant and should be included in the total project budget. Underfloor heating is ideal for heat pumps because it operates well at low flow temperatures, but retrofitting underfloor heating is expensive and disruptive and is generally only practical during a full renovation rather than a standalone heat pump installation.
Can a heat pump also provide hot water?
Yes. Most domestic heat pump systems include a hot water cylinder and use the heat pump to heat both the space heating circuit and the domestic hot water. The heat pump heats the cylinder to a lower temperature than a conventional boiler, typically 50 to 55 degrees Celsius for daily use, with a weekly legionella prevention cycle to at least 60 degrees (usually run by the heat pump or a backup immersion heater). This is sufficient for normal domestic hot water use. The hot water cylinder is typically larger than the standard cylinder in a gas-heated property, commonly 200 to 300 litres, and the cylinder and installation cost are usually included in the heat pump installation quote.
If the property has a combi boiler with no separate hot water cylinder, installing a heat pump will require finding space for a cylinder, which is a consideration for smaller properties. The heat pump system cost in this calculator is intended to include the cylinder and all associated pipework and controls as a complete installation, but this should be confirmed with the installer when obtaining a quote. Some households with solar panels find that combining a solar diverter with the heat pump system, which uses surplus solar generation to heat the hot water cylinder, reduces hot water running costs further and is worth discussing with the installer if solar panels are already installed or planned.
Squaring Up
The heat pump running cost question has an honest answer that depends on your current fuel and the tariff picture at the time. For oil and LPG properties, the annual saving is typically real and meaningful: the narrower gap between electricity and these fuel prices means a heat pump operating at SCOP 2.8 or above usually produces a genuine reduction in running costs, and the higher BUS grant of £9,000 (until March 2027) strengthens the capital case further. For gas properties, the running cost comparison depends on the electricity-to-gas price ratio, which changes quarterly: at some tariff levels a well-insulated property breaks even or saves money, at others there is a modest additional cost. The financial case for switching from gas often rests on the BUS grant reducing the capital cost and the potential of a heat pump-specific tariff to reduce electricity costs.
Insulation before installation is not an optional extra: it directly affects the SCOP the heat pump achieves, the size of system needed, and the running cost outcome. A heat pump in a poorly insulated property is likely to disappoint on running costs. Getting the insulation right first, then sizing the heat pump for the insulated property, produces the best financial and operational outcome.
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Guides, calculators, and comparators covering every aspect of home improvement finance Explore guides and toolsUpdate log: July 2026
What changed in this update
Fuel and electricity rates updated to reflect current UK energy prices. The calculator now lets you adjust your current fuel unit rate directly rather than using a fixed default, and shows the assumed boiler efficiency for your fuel type. The Boiler Upgrade Scheme section was updated to reflect the April 2026 overhaul: the EPC requirement has been removed, oil and LPG properties now qualify for a higher £9,000 grant (until March 2027), and the scheme has been extended to 2030. The running cost comparison narrative was revised to reflect that the gas-to-heat-pump outcome depends on the electricity-to-gas price ratio at the time, which changes quarterly, rather than stating a single breakeven SCOP figure. SCOP context was added, referencing the 2025–26 national average of 3.4 from Energy Systems Catapult / MCS data.
The calculator now includes a show-the-working section that displays the full calculation chain from annual bill to heat pump running cost, including the breakeven SCOP for your inputs. Accessibility improvements include higher-contrast colours throughout the tool, ARIA labels and live regions for screen reader compatibility, larger touch targets for mobile use, and a reduced-motion media query. Two additional tools were added to the related tools section: the home energy upgrade sequencer and the insulation savings calculator. Heat pump tariff guidance was updated to reference current dedicated tariff rates.
This tool is for illustrative purposes only and does not constitute financial or energy advice. All running cost estimates are based on illustrative fuel and electricity prices and estimated SCOP values, which will differ from actual figures depending on your specific installation, property construction, usage patterns, and tariff. The Boiler Upgrade Scheme is subject to eligibility and funding availability: verify current status on GOV.UK before incorporating the grant into any budget. Heat pump sizing should always be carried out by an MCS-certified installer using a full heat loss calculation. Your home may be at risk if you do not keep up repayments on a secured loan.
