Running costs · 2025 data
Heat Pump Running Costs UK 2025: By Property Type and Tariff
Real running cost data for UK heat pumps in 2025 — by property size, fuel comparison, and tariff. The £600–£900/year saving vs gas is real, but only on the right tariff.
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UK kitchen table with energy bills, a smart meter display, and a calculator — household running cost comparison setting, natural light
Running cost is the single most asked-about figure when homeowners consider switching from a gas boiler to a heat pump. It’s also the most misrepresented. Heat pump manufacturers quote idealised numbers from sunny lab conditions; sceptics quote worst-case scenarios from poorly insulated homes on the wrong tariff. The truth, as usual, sits in between — and depends mostly on factors the heat pump itself doesn’t control.
This is what running costs actually look like in 2025, across a range of UK property types and tariffs.
The numbers in one table
For a typical 3-bed semi consuming 12,000 kWh of useful heat per year:
| System | Tariff | Cost per kWh useful heat | Annual cost |
|---|---|---|---|
| ASHP (SCOP 3.2) | Octopus Cosy | £0.075 | £900 |
| ASHP (SCOP 3.2) | Standard variable | £0.082 | £984 |
| GSHP (SCOP 4.0) | Octopus Cosy | £0.060 | £720 |
| New gas boiler (91% efficient) | Ofgem cap | £0.085 | £1,020 |
| 15-year gas boiler (82% efficient) | Ofgem cap | £0.094 | £1,128 |
| Oil boiler | Current oil price | £0.105 | £1,260 |
| LPG boiler | Current LPG price | £0.155 | £1,860 |
| Direct electric storage | Economy 7 off-peak | £0.16 | £1,920 |
The headline: a heat pump on the right tariff saves £100–£400 per year vs gas, and £400–£900 per year vs oil/LPG.
Why tariff matters more than the heat pump
The single biggest variable in heat pump running costs isn’t the heat pump itself. It’s whether you’re on a heat-pump-optimised tariff or a standard variable tariff.
Heat-pump tariffs like Octopus Cosy charge ~7p/kWh during three daily off-peak windows. Modern heat pumps and hot water cylinders can be set to do the bulk of their work during these windows, drastically reducing your average per-kWh cost.
On a standard variable tariff (Ofgem default cap), you pay 24–27p/kWh round the clock. The heat pump still saves you energy compared to a gas boiler (because SCOP), but the unit cost difference between electricity and gas eats most of the saving.
| Tariff | Cosy savings vs gas | Standard savings vs gas |
|---|---|---|
| Heat-pump-optimised (Cosy) | £200–£400/yr | — |
| Standard variable | — | £20–£100/yr |
If you can’t or won’t switch to a heat-pump tariff, the running-cost case for a heat pump weakens significantly. It still wins on carbon. It rarely wins on cost.
Why insulation matters even more
Heat pumps are at their best in well-insulated homes. They run continuously at low flow temperatures, which suits a steady, modest heat load. Poorly insulated homes need more heat overall, push the heat pump harder, and bring SCOP down.
For the same 3-bed semi at three insulation levels:
| Insulation level | Heat demand | ASHP cost on Cosy | Saving vs new gas |
|---|---|---|---|
| Good (EPC C+, modern double glazing, cavity, loft) | 10,200 kWh | £765 | £282 |
| Average (EPC D, basic insulation) | 12,000 kWh | £900 | £120 |
| Poor (EPC E or below, single glazing, solid walls) | 15,000 kWh | £1,125 | £45 |
In the poor-insulation case, the heat pump barely beats a new gas boiler on running cost. The economic case rests almost entirely on the BUS grant offsetting the install cost premium.
The implication: insulation first, heat pump second. ECO4 may fund the insulation for free if you qualify. Even if you self-fund, every £1 spent on insulation typically generates more lifetime saving than the equivalent £1 spent on heat pump premium efficiency.
By property type
For broadly average insulation, on the Octopus Cosy tariff:
| Property | Useful heat demand | ASHP cost | New gas cost | Saving |
|---|---|---|---|---|
| 1-bed flat | 5,000 kWh | £375 | £425 | £50 |
| 2-bed terrace | 8,000 kWh | £600 | £680 | £80 |
| 3-bed semi | 12,000 kWh | £900 | £1,020 | £120 |
| 4-bed detached | 16,000 kWh | £1,200 | £1,360 | £160 |
| 5+ bed / large | 22,000 kWh | £1,650 | £1,870 | £220 |
Larger homes save more in absolute terms because their heat demand is higher. But percentage saving is roughly constant — around 12% of running cost.
When heat pumps lose on running cost
There are scenarios where running cost goes the wrong way:
- Heat pump on standard variable, replacing a new gas boiler in a well-insulated home. Cost is similar or slightly worse than gas.
- Heat pump in a poorly insulated solid-wall property. SCOP drops, electricity demand rises, savings disappear.
- Heat pump used in “boost” mode (high flow temp, on-demand heating). Defeats the technology — drives SCOP down.
- Heat pump in a holiday home left cold and heated rapidly on arrival. Heat pumps reward continuous low-temperature operation, not infrequent boost cycles.
None of these are typical. They do happen.
What we don’t include (and why it matters)
Our running cost figures cover energy bills only. We don’t include:
- Maintenance. Roughly £80–£150/yr for both gas boilers and heat pumps. Effectively cancels out.
- Equipment replacement at end of life. Heat pump unit ~£3,000–£5,000 every 15–20 years. Boiler ~£2,500 every 10–15 years. Heat pump premium per year is comparable.
- Future carbon pricing on gas. Likely to apply by 2030. Would worsen gas running costs, widen heat pump advantage.
- Property value impact. EPC uplift from C to B can add £5,000–£15,000 to a UK home’s value. Not in running cost — but real money.
Including all of these tilts the picture further toward heat pumps over a 10-year horizon. The headline running cost numbers are conservative.
The bottom line
For a typical UK 3-bed semi on the Octopus Cosy tariff, a well-installed air source heat pump saves £120 per year vs a new gas boiler, £400 per year vs a 15-year-old gas boiler, and £800 per year vs oil. Most of those savings come from the tariff arbitrage, not the heat pump itself.
If you’ll switch to a heat-pump tariff and your home is reasonably insulated, the numbers work. If neither of those is true, you’re buying a heat pump for carbon reasons, not cost — perfectly valid, but be clear-eyed about it.
Run your own numbers in the cost calculator — yours may differ from this average.