Our worked example costs about £979 a year for space heating, or £1,274 including hot water. It assumes 12,000 kWh of space heat at SCOP 3.2 and 2,600 kWh of hot-water heat at COP 2.3. These are modelling assumptions, not a quote for every three-bedroom home. We use Ofgem’s July to September 2026 average Direct Debit rates; your regional tariff and future rates may differ.
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- Our space-heating example costs £979 a year - this assumes 12,000 kWh of useful heat, SCOP 3.2 and electricity at 26.11p/kWh.
- Hot water adds £295 in this example - 2,600 kWh of hot-water heat at COP 2.3 brings the combined energy cost to £1,274.
- Compare the same heat demand - a gas boiler at 90% efficiency costs £977 for the same space heating, before standing charges and servicing.
- Compare every tariff period - cheap hours help only when your actual consumption shifts enough to offset peak rates and other charges.
- Solar savings need a separate model - estimate electricity used directly by the heat pump, seasonal overlap and foregone export income before claiming a saving.
How Much Does a Heat Pump Cost to Run?
For an illustrative annual space-heating demand of 12,000 kWh, an ASHP at SCOP 3.2 uses 3,750 kWh of electricity. At 26.11p/kWh, that costs £979 before hot water, standing charges and maintenance.
Heat pump running costs depend on two things above all else: how much electricity you use, and how efficiently your heat pump converts that electricity into heat. That efficiency is measured as the Seasonal Coefficient of Performance – or SCOP.
We put the two systems side by side in our heat pump vs gas boiler comparison.
SCOP measures heat output divided by electricity input over a season. It is an energy ratio, not a ratio of pounds spent. To compare fuel costs, divide electricity price by SCOP and gas price by boiler efficiency. With electricity at 26.11p/kWh, gas at 7.33p/kWh and a 90%-efficient boiler, the break-even SCOP is about 3.21. Your measured performance matters more than a product headline.
The real-world average SCOP for UK air source heat pumps is around 3.2, according to data from the Electrification of Heat demonstration project. High-performance units from manufacturers such as Daikin, Mitsubishi, and Vaillant – properly installed and sized – regularly achieve SCOP 3.5 or higher. Our best air source heat pumps guide compares SCOP ratings across every major brand. Poorly sized or badly commissioned systems can fall to SCOP 2.5–2.8, at which point they become noticeably more expensive to run than a gas boiler.
| Property Type | Annual Heat Demand (kWh) | Electricity Consumed (kWh) | Annual Cost (SCOP 2.8) | Annual Cost (SCOP 3.2) | Annual Cost (SCOP 3.5) |
|---|---|---|---|---|---|
| 1–2 bed flat | 7,500 | 2,344–2,679 | £699 | £612 | £560 |
| 3 bed semi-detached | 12,000 | 3,750–4,286 | £1,119 | £979 | £895 |
| 4 bed detached | 18,000 | 5,143–6,429 | £1,679 | £1,469 | £1,343 |
| 5+ bed large detached | 26,000 | 7,429–9,286 | £2,425 | £2,121 | £1,940 |
The property labels above are illustrative scenarios, not verified housing-stock averages. Use a heat-loss calculation or measured annual demand for your own property. All costs use the same July to September electricity rate and exclude hot water. The monthly example below adds a separate hot-water allowance.
Heat Pump vs Gas Boiler Running Costs
At the same 12,000 kWh space-heating demand, our gas example costs £977 and the SCOP 3.2 heat pump costs £979. Fuel-only costs are almost equal under these assumptions; installation cost, maintenance and standing charges need separate comparison.
Gas is still cheaper per unit of delivered heat at current UK energy rates – but by less than most people think. A modern condensing gas boiler at 90% efficiency costs around 8.14p per kWh of useful heat delivered (7.33p ÷ 0.90). An ASHP at SCOP 3.2 costs 8.16p per kWh of heat (26.11p ÷ 3.2). That’s essentially price parity at current rates – and any unit achieving a SCOP above 3.3 delivers heat cheaper than gas.
What narrows the real-world gap? Standing charges, maintenance costs, and the direction of travel on tariffs. Heat pump tariffs offering 13–16p/kWh off-peak electricity already flip the economics in the heat pump’s favour for well-insulated homes. And the government’s long-term policy direction – rising carbon costs on gas, declining electricity rates from renewable oversupply – means the gap will likely close further over a heat pump’s 15–20 year lifespan.
| System and assumed efficiency | Fuel unit rate | Cost per kWh of useful heat | Annual space-heating energy cost |
|---|---|---|---|
| ASHP, SCOP 2.8 | 26.11p/kWh | 9.32p | £1,119 |
| ASHP, SCOP 3.2 | 26.11p/kWh | 8.16p | £979 |
| ASHP, SCOP 3.5 | 26.11p/kWh | 7.46p | £895 |
| Gas boiler, 90% efficiency | 7.33p/kWh | 8.14p | £977 |
| Direct electric heating | 26.11p/kWh | 26.11p | £3,133 |
| GSHP, SCOP 4.0 | 26.11p/kWh | 6.53p | £783 |
The comparison covers energy for space heating only. Add your actual service quote and standing charges separately. A home usually keeps an electricity supply whichever heating system it uses, so its full electricity standing charge is not automatically an extra heat-pump cost. Gas standing charges can only be avoided if the gas supply is removed. Obtain current oil or LPG prices before comparing those fuels.
At SCOP 3.5, a well-installed ASHP costs just £100–£150/year more than gas when including standing charges and maintenance. For homes off the gas grid (oil or LPG), an ASHP at SCOP 3.2 is already cheaper to run. Ground source heat pumps at SCOP 4.0 beat gas on fuel costs alone - but come with a significantly higher installation price.
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Electricity Rates for Heat Pump Owners
A time-of-use tariff can reduce costs if its cheap periods match your heating needs. Compare the full bill using half-hourly consumption, including peak rates, standing charges and electricity used by other appliances.
For a simple comparison, multiply consumption in each price period by that period’s rate, then add the standing charge. Do this for both tariffs using the same usage profile. Do not multiply the entire year’s heating consumption by an off-peak rate unless the system can actually run entirely within those hours.
Octopus Agile and Octopus Intelligent Go deserve a special mention. Agile links electricity prices directly to the wholesale market in 30-minute slots, with prices regularly dropping to 1–5p/kWh overnight. Intelligent Go charges a fixed 8p/kWh for 6 hours of overnight cheap charging, automatically scheduled via smart meters and electric vehicle chargers – and increasingly, heat pump controllers. For tech-savvy owners, these tariffs can push effective heat pump costs below gas rates even at current electricity prices.
| Tariff feature | What to check |
|---|---|
| Cheap periods | Which hours apply, and how much heat-pump use falls within them? |
| Peak rate | Will evening heating and household use cancel out cheap-hour savings? |
| Eligibility | Check your meter, heating system and any installation or equipment restrictions. |
| Rate changes | Confirm whether the tariff is fixed or variable and when its prices may change. |
Cosy Octopus currently has cheap windows at 04:00-07:00, 13:00-16:00 and 22:00-00:00. Those hours are 51% below its regional day rate, while 16:00-19:00 is 50% above it. Check a postcode quote and meter compatibility. This describes one tariff’s structure, not a guarantee of savings or a market-wide comparison.
Switching to a heat pump-specific tariff is the single highest-return action for reducing running costs, ahead of insulation upgrades or hardware changes. Octopus Intelligent Go at 8p/kWh off-peak makes an ASHP at SCOP 3.2 significantly cheaper than gas on fuel cost per kWh of heat delivered.
What Affects Heat Pump Running Costs?
Insulation affects heat demand, while radiator sizing and flow temperature affect the efficiency needed to meet it. Assess them together before estimating a change in annual bills.
Heat pump running costs are far more sensitive to installation quality and property characteristics than gas boilers. A gas boiler can compensate for poor insulation by simply burning more gas – the penalty is linear. A heat pump’s SCOP degrades non-linearly as it works harder: a poorly insulated home forces the heat pump to run at higher flow temperatures, directly reducing COP. Understanding the six key variables below gives you a clear hierarchy of interventions.
Insulation
Two houses with the same bedroom count can have very different heat demand. Compare the building’s heat-loss calculation and measured use before assuming an EPC band produces a particular bill. See our installation cost guide when budgeting for the system and any building work.
Ask an assessor which insulation measures suit your walls, roof and floors, and how ventilation will be maintained. The order of work depends on existing insulation and condition. Window upgrades may be part of that assessment, but compare their cost and benefit with other measures. Check available grants before committing to work.
Radiator Sizing
Heat pumps work most efficiently at low flow temperatures – typically 35–45°C, compared to 60–70°C for a gas boiler. At lower flow temperatures, your radiators need to be 1.5–2.5 times larger to deliver the same heat output. If your existing radiators are undersized for low-temperature operation, the heat pump controller will raise the flow temperature to compensate, directly reducing the COP. Every 10°C increase in flow temperature reduces COP by approximately 15–20%. A proper heat loss calculation per room, conducted by an MCS-accredited installer, should identify which radiators need upgrading. Replacing 3–5 undersized radiators (typically £150–£300 per radiator installed) can improve real-world SCOP by 0.3–0.5, saving £100–£180/year.
Flow Temperature
Flow temperature – the temperature of water leaving the heat pump for the heating circuit – is the most direct lever on running costs. Every 1°C reduction in flow temperature improves COP by 2–3%. Moving from a flow temperature of 50°C to 40°C (with appropriately sized radiators) can improve SCOP from 2.8 to 3.4 – a difference of approximately £210/year for a 3-bed semi.
Modern heat pump controllers from Vaillant, Daikin, and Mitsubishi allow flow temperature to be set and viewed directly. The target for maximum efficiency is the lowest flow temperature at which your home reaches the set-point temperature on the coldest expected day of the year in your area. In well-insulated UK homes, 35–42°C is typically achievable; in older, less insulated properties, 50–55°C may be required.
Thermostat Settings
Heat pumps are designed to run continuously at a low level rather than cycling on and off like gas boilers. Setting back the temperature aggressively overnight or when out – as you would with a gas boiler – forces the heat pump to reheat a cold building, running at higher compressor speeds and lower efficiency. The recommended approach is a maximum 2°C setback overnight (e.g. 19°C overnight vs 21°C daytime) and to avoid setback during the working day in well-insulated homes. A “set and forget” approach at a constant comfortable temperature typically costs 5–10% less than aggressive setback scheduling for heat pump users, contrary to the conventional wisdom applied to gas boilers.
Hot Water Demand
Heat pumps producing domestic hot water (DHW) operate at a COP of 2.0–2.5 rather than the space heating SCOP of 3.0–3.5. This is because hot water requires a higher tank temperature (typically 55–60°C for Legionella prevention), which degrades heat pump performance significantly. A family of four with average hot water usage (approximately 2,500–3,000 kWh/year for DHW) will spend an additional £260–£390/year on hot water production at Q3 2026 electricity rates.
Solar PV can supply some heat-pump electricity when generation and demand coincide. Estimate the overlap month by month, rather than claiming a fixed percentage reduction in annual heating cost. Compare direct heat-pump use, cylinder heating, battery losses and the export payment you give up. Our solar cost guide covers the separate investment.
Defrost Cycles
Air source heat pumps extract heat from outdoor air, which means that in cold, damp conditions (typically between −5°C and +7°C), ice can form on the outdoor unit’s evaporator coil. The heat pump periodically reverses its refrigerant cycle to defrost the coil – a process that consumes electricity and temporarily interrupts heating. Defrost cycles typically add 5–15% to electricity consumption during the coldest winter months (January and February in most of the UK).
Over a full heating season, defrost accounts for approximately 3–7% of total electricity use. This is already factored into the SCOP figure from manufacturers, but real-world results can differ if the heat pump is located in a particularly damp or north-facing position with restricted airflow around the outdoor unit.
Heat Pump Maintenance Costs
Annual heat pump servicing costs £150–£300. Budget £200/year for maintenance – significantly less than a gas boiler, with no annual Gas Safe inspection required.
Heat pump maintenance is simpler and generally less expensive than gas boiler maintenance. There is no combustion process to inspect, no annual Gas Safe engineer requirement, and no risk of carbon monoxide. The typical annual service involves checking refrigerant pressure, inspecting electrical connections, cleaning filters, verifying flow temperatures, and testing defrost cycles. A qualified F-Gas-registered engineer should carry out any work involving the refrigerant circuit; general servicing can be done by a trained heat pump engineer who does not need to be Gas Safe registered.
| Service Item | Frequency | Typical Cost | DIY Possible? |
|---|---|---|---|
| Annual service (full) | Yearly | £150–£300 | No – requires qualified engineer |
| Air filter cleaning | Every 3–6 months | £0 | Yes – owner task |
| Outdoor unit cleaning | Twice yearly | £0 | Yes – gentle hose wash |
| Glycol (antifreeze) top-up | Every 2–3 years | £80–£150 | No – requires specialist |
| System pressure check & re-pressurise | As needed | £50–£100 | Partial (top-up yes, investigation no) |
| Refrigerant pressure check | Yearly (via service) | Included in annual service | No – F-Gas only |
For budgeting purposes, £200/year is a reasonable average maintenance allowance for an air source heat pump in normal UK conditions. This is comparable to a gas boiler (£80–£150/year service plus parts), particularly once you factor in the absence of Gas Safe and carbon monoxide detector requirements.
Repair Costs by Fault Type
| Fault Type | Typical Repair Cost | Frequency | Notes |
|---|---|---|---|
| Refrigerant leak (minor top-up) | £200–£500 | Occasional | F-Gas engineer required; includes leak location |
| Refrigerant leak (major repair) | £500–£1,200 | Uncommon | Includes coil repair and recharge |
| PCB (control board) replacement | £400–£900 | Uncommon | Parts alone £200–£500 depending on brand |
| Compressor replacement | £1,200–£2,500 | Rare (mid-life) | Major repair – consider full replacement if >12 years old |
| Circulation pump replacement | £200–£450 | Occasional | Typically 8–12 year lifespan |
| Expansion vessel replacement | £150–£300 | Occasional | 5–8 year typical lifespan |
Air source heat pumps have a design lifespan of 15–20 years, with the compressor being the main limiting component. Manufacturers including Daikin, Mitsubishi, and Vaillant typically offer 5–7 year warranties on the unit, with extended warranties available on registration. After the warranty period, budgeting £150–£250/year as a repair reserve is prudent, in addition to the annual service cost.
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How Smart Controls Reduce Running Costs
Weather compensation and smart scheduling can improve real-world SCOP by 10–15%, saving £100–£180/year in a 3-bed semi at current electricity rates.
Smart controls for heat pumps go beyond basic scheduling. The most impactful feature is weather compensation – automatically adjusting the flow temperature based on outdoor temperature. On a mild day (10°C), a heat pump might only need to produce 35°C flow temperature to maintain comfort; on a cold day (−5°C), it may need 50°C. Without weather compensation, the heat pump runs at a fixed, often conservative flow temperature, wasting energy on mild days. With a correctly configured weather compensation curve, the heat pump automatically finds the lowest efficient flow temperature for any given weather condition. This alone can improve SCOP by 0.2–0.4 in typical UK conditions.
Manufacturer Apps and Controllers
Most major heat pump brands now include smart control capability as standard or as an optional add-on. Vaillant’s sensoAPP provides real-world COP monitoring, weather compensation control, and energy reporting via smartphone. Daikin’s Onecta app offers comparable functionality with zone control for multi-room systems and direct integration with Daikin smart thermostats. Mitsubishi’s MELCloud platform is particularly well-regarded for its detailed energy monitoring, allowing owners to track efficiency against weather data and identify degradation over time. All three support tariff-based scheduling for off-peak operation.
Third-Party Smart Thermostat Compatibility
Third-party smart thermostats add a layer of scheduling intelligence beyond the manufacturer app. tado° is the most widely compatible option, supporting OpenTherm or on/off control of most heat pump brands and offering geofencing (auto setback when everyone leaves home), AI-based weather adaptation, and detailed energy reporting. Nest (Google) thermostats are generally compatible with heat pumps via standard on/off connections but lack OpenTherm integration on many models, which limits their ability to modulate flow temperature.
Hive thermostats are explicitly not certified for use with heat pumps by most manufacturers and may void warranty if used to control a heat pump directly. For maximum efficiency gains, an OpenTherm-compatible thermostat from tado° or the manufacturer’s own system is the recommended choice.
Tariff Integration and Scheduling
Schedule heating around the actual tariff windows and the needs of the household. Monitor indoor comfort and total consumption after changing a schedule. Pre-heating is useful only if the building retains enough heat and the electricity saved outweighs any extra heating required.
Integration between heat pump controllers and tariff APIs is improving: Octopus Energy’s Kraken platform offers direct integration with compatible heat pump models, automatically scheduling operation for the cheapest grid windows. This “smart charging” approach – equivalent to what EV owners already do – can meaningfully cut effective running costs compared to unmanaged operation, with the exact saving depending on your tariff and how much of your usage shifts to off-peak hours.
Daily and Monthly Running Cost Breakdown
The combined model averages about £106 a month, but winter months use more electricity than summer. A monthly average is a budgeting figure, not an expected bill for each month.
Heat pump costs are not evenly distributed across the year. Approximately 80% of space heating energy is consumed between October and March, with the heating season peaking in January and February. The summer months contribute almost nothing to heating costs, though the heat pump will still use electricity for hot water year-round. Understanding the monthly shape of costs helps with budgeting and makes it easier to assess whether switching tariff makes sense in your situation.
The monthly illustration uses the same 12,000 kWh of annual space heat and SCOP 3.2 as the comparison above. Hot-water demand totals 2,600 kWh of useful heat at COP 2.3. The seasonal distribution is an explicit example, not measured household data.
| Month | Space heat, kWh | Electricity including hot water, kWh | Energy cost |
|---|---|---|---|
| January | 2,300 | 814.8 | £212.73 |
| February | 2,000 | 711.7 | £185.83 |
| March | 1,500 | 564.8 | £147.46 |
| April | 850 | 358.5 | £93.61 |
| May | 250 | 174.1 | £45.47 |
| June | 0 | 92.9 | £24.26 |
| July | 0 | 96.0 | £25.07 |
| August | 0 | 96.0 | £25.07 |
| September | 300 | 186.7 | £48.74 |
| October | 1,000 | 408.5 | £106.66 |
| November | 1,750 | 639.8 | £167.05 |
| December | 2,050 | 736.6 | £192.34 |
| Full year | 12,000 | 4880.4 | £1274.28 |
The annual combined energy cost is £1,274, rounded from £1,274.28. Space heating contributes £979.13 and hot water £295.16. Monthly rows use unrounded consumption, so displayed totals can differ slightly through rounding. The model holds July to September prices constant for comparison; it is not a forecast of every future quarter. Add your actual standing charges and maintenance separately.
How to Reduce Heat Pump Running Costs
Start by measuring consumption and checking that the system meets your comfort needs. Ask the installer to review the controls and flow temperature before buying extra equipment. Savings from different measures overlap, so do not add individual estimates together as though each were independent.
The good news for heat pump owners is that many of the biggest savings require no capital outlay – just adjustments to settings and tariff choices. The actions below are ranked roughly by ease-to-impact ratio, with the quickest wins first.
| Action | Difficulty | How to Do It |
|---|---|---|
| Switch to heat pump tariff | Easy | Compare current tariff terms against your measured consumption |
| Reduce flow temperature by 5–10°C | Easy | Adjust via manufacturer app; check rooms still reach set-point on coldest days |
| Enable weather compensation | Easy–Moderate | Check if controller supports it; may need installer to configure the compensation curve |
| Add/upgrade loft insulation | Easy–Moderate | 300mm mineral wool; many homes qualify for free insulation via ECO4 scheme |
| Install tado° smart thermostat | Moderate | Geofencing auto-setback + smart schedule; use OpenTherm connection if available |
| Schedule hot water for off-peak | Easy | Set DHW schedule via manufacturer app to run during your tariff’s actual cheap-rate windows |
| Upgrade 2–3 undersized radiators | Moderate | Focus on rooms that never reach set-point – a sign the radiator is undersized for low-temp operation |
| Insulate hot water cylinder | Easy | Fit an 80mm cylinder jacket if not already insulated; heat loss can be 1–2 kWh/day on uninsulated cylinders |
| Add cavity wall insulation | Professional | Check cavity via borescope; ECO4 free if household meets eligibility; 3–5 year payback otherwise |
| Annual professional service | Easy | Refrigerant check and flow temperature optimisation at service prevents gradual SCOP degradation |
The highest-impact trio: (1) switch to a dedicated heat pump tariff - saves £250–£500/year at zero cost; (2) reduce flow temperature to the lowest setting your home can tolerate - saves £80–£180/year at zero cost; (3) upgrade loft insulation if below 270mm - saves £100–£200/year for £300–£600. Combined, these three changes can cut annual heat pump running costs by £430–£880 without touching the heat pump unit itself.
If your heat pump was installed more than 3 years ago and your bills have been higher than expected, the most likely culprits are an incorrectly configured flow temperature curve, an out-of-date tariff, or refrigerant pressure slightly below specification – all of which are addressable in a single engineer visit. Request a “performance optimisation service” rather than a standard annual check, and ask the engineer to measure actual SCOP from your electricity meter data against your heat demand.
