Heat Pump Savings by Previous Fuel: Worked UK Examples

How much a heat pump saves depends above all on what you are heating with now. Rather than quote anecdotes, this page works through the same home on each fuel, using the Ofgem price cap for 1 October 2026 to 31 December 2026 and an indicative heating oil price. These are worked examples, not reports from individual homeowners, so you can follow the sums and swap in your own figures.

The Example Home

The example home needs 11,500 kWh of heat a year for heating and hot water, roughly a typical semi-detached house. The heat pump runs at a seasonal COP of 3.2, so it uses about 3,594 kWh of electricity. Fossil fuel boilers are taken as 90% efficient. Prices: electricity 26.32p/kWh, gas 7.97p/kWh (Ofgem price cap, Direct Debit, GB average, 1 October 2026 to 31 December 2026), heating oil about 11.4p/kWh (roughly 117p per litre including VAT, October 2026, indicative BoilerJuice average). Standing charges are left out unless stated.

Switching from Gas: A Small Running-Cost Saving

Gas: 11,500 kWh ÷ 0.9 = 12,778 kWh × 7.97p = about £1,018 a year. Heat pump: 3,594 kWh × 26.32p = about £946 a year. The saving on unit rates is about £72 a year. If you also disconnect the gas supply, you stop paying the gas standing charge (29.68p a day, about £108 a year), taking the saving to about £180.

The result is sensitive to efficiency. At a seasonal COP of 2.8 the heat pump would cost about £1,081, slightly more than gas; at 3.5 it would cost about £865. A heat pump or time-of-use tariff can lower the cost further, but check the supplier's current rates for your area. Against gas, the case for a heat pump rests more on comfort, carbon and future prices than on large immediate savings.

Switching from Oil: A Larger Saving

Oil: 12,778 kWh × 11.4p = about £1,457 a year, against about £946 for the heat pump: a saving of about £510 a year. A bigger home using 15,000 kWh of heat would save about £670. Heating oil is not price-capped, and DESNZ figures show it rose sharply in 2026, so use your own last delivery price.

Oil homes without mains gas can get a £9,000 Boiler Upgrade Scheme grant for an air-to-water or ground source heat pump, from 21 July 2026 to 31 March 2027 (England and Wales). That brings the median installed price down to about £3,900 (DESNZ, 2026 Q2), which the example saving repays in roughly seven to eight years, sooner if you would otherwise be replacing an old oil boiler.

Switching from LPG: Use Your Own Price

We have not found a reliable current national price for bulk domestic LPG, so we do not quote one. LPG holds roughly 7 kWh per litre, so the example home would buy about 1,825 litres a year (12,778 kWh ÷ 7). Multiply that by your price per litre from your last delivery and compare it with about £946 for the heat pump. Remember tank rental if you pay it. LPG homes off the gas grid qualify for the same £9,000 grant as oil homes until 31 March 2027.

Switching from Electric Heating: The Biggest Saving

Storage heaters and direct electric heating turn one kWh of electricity into about one kWh of heat. At the standard capped rate, 11,500 kWh would cost about £3,027 a year; a heat pump needs only about a third as much electricity, so it costs about £946. If you are on Economy 7 and most of your heating uses the cheaper night rate, your current cost is lower and the saving smaller, so check your own bills.

Adding Solar Panels

Solar panels can supply part of a heat pump's electricity, especially for hot water in spring and summer. They generate least in winter, when heating demand is highest, so the saving on space heating is limited unless you also have a battery or a tariff that rewards shifting use. Model solar separately rather than assuming it makes heating free.

Savings Summary Table

Worked example: 11,500 kWh of heat a year, 90% boiler efficiency, heat pump seasonal COP 3.2. Ofgem price cap 1 October 2026 to 31 December 2026; oil indicative, October 2026. Unit rates only unless stated. Last reviewed October 2026.

What Affects Your Savings

Your savings will depend on several factors:

The single biggest factor is what you are currently heating with. Electric heating and oil users save the most; against mains gas the running-cost difference is small. In all cases, good insulation, correct commissioning and a suitable electricity tariff improve the numbers.

Frequently Asked Questions

How much does a heat pump save compared with gas?

Not much on running costs alone. On our standard example (11,500 kWh of heat a year, heat pump seasonal COP 3.2, 90% efficient gas boiler) a heat pump costs about £946 a year at the October 2026 price cap against about £1,018 for gas on unit rates, a saving of about £72. If you also drop the gas supply and its standing charge (29.68p a day), the saving rises to about £180. A less efficient heat pump can cost more than gas.

How much does a heat pump save compared with oil?

On the same example, oil at about 11.4p/kWh (roughly 117p per litre, October 2026, indicative) in a 90% boiler costs about £1,457 a year, against about £946 for the heat pump: a saving of about £510. Heating oil is not price-capped, so use your own last delivery price.

What about LPG?

We have not found a reliable current national price for bulk domestic LPG, so we do not quote one. On the example you would buy about 1,825 litres a year (12,778 kWh at roughly 7 kWh per litre). Multiply that by your price per litre and compare it with about £946 for the heat pump.

Are these real homeowners' figures?

No. They are worked examples calculated from the Ofgem price cap for 1 October 2026 to 31 December 2026 and an indicative oil price, so you can see how the sums work. Your result depends on your heat demand, your heat pump's real efficiency and your tariff.

What affects how much I save?

Mainly the fuel you are replacing, how much heat your home uses, how efficiently the heat pump runs (its seasonal COP), and your electricity tariff. Better insulation and correct commissioning both help.

What if I don't save money?

Check the flow temperature and weather compensation settings, your electricity tariff and your insulation. A commissioning check by a competent engineer often finds the problem.