Compare annual heat-pump and gas-boiler running costs from heat demand, SCOP, fuel prices, and standing charges, with separated cost rows.
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Heat pump running cost comparison Compare annual heat pump and gas boiler running costs from heat demand, tariffs, boiler efficiency, and seasonal COP, then test the two assumptions competitors usually blur together: whether you still pay a gas standing charge and what SCOP is required to beat gas at the entered electricity rate.
Quick starting points
Assumptions to review before trusting the result
Annual heat demand: use delivered heat, not whole-home electricity use. EPC estimates or heating-only gas use are usually a better starting point than total bill cost.
Seasonal COP: SCOP should reflect real installed performance across winter, not the headline lab COP from a brochure.
Tariff treatment: the gas standing charge is a major part of the answer when comparing a full switch against a home that keeps gas connected.
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Switch the money display without changing the energy maths.
Annual extra cost with heat pump
$98
Under these assumptions, the gas boiler is cheaper to run over a full year.
That is 11.0% higher than the gas-boiler annual cost.
$889
Gas annual cost
$987
Heat pump annual cost
$74
Gas monthly equivalent
$82
Heat pump monthly equivalent
3.33
Required SCOP to match gas
$106
Net annual standing-charge change
System comparison sheet
These rows separate fuel spend from standing charges so you can see whether the result is driven mainly by tariff ratio, SCOP, or whether the gas standing charge disappears after the switch.
System
Energy used
Fuel cost
Standing charges
Annual cost
Cost per kWh heat
Gas boiler
13,636 kWh
$783
$106
$889
$0.0741
Air-source heat pump
4,000 kWh
$987
$0
$987
$0.0822
Heat pump sensitivity by seasonal COP
These rows hold the same electricity tariff and annual heat demand, then show how the heat pump running cost changes as seasonal COP moves up or down.
SCOP
Electricity use
Annual cost
Saving vs gas
2.5
4,800 kWh
$1,184
-$295
3.0
4,000 kWh
$987
-$98
3.5
3,429 kWh
$846
$43
4.0
3,000 kWh
$740
$149
Break-even electricity price $0.2222 per kWh. At or below this tariff, the entered heat-pump assumptions match the gas-boiler running cost with the current standing-charge assumption.SCOP threshold at the entered tariffs The heat pump needs a seasonal COP of about 3.33 to match the gas boiler at the current gas and electricity prices. If your expected installed SCOP is lower, gas stays cheaper on running cost alone.
Heat pump running cost calculator: gas boiler vs air-source heat pump comparison
Whether a heat pump is cheaper to run than a gas boiler depends on your annual heat demand, your gas and electricity unit prices, your boiler efficiency, and the heat pump seasonal coefficient of performance (SCOP). This calculator compares annual heating running costs for both systems, shows how the result changes across common SCOP values, and identifies the electricity price at which a heat pump reaches cost parity with gas.
How running costs are calculated
Gas boiler annual fuel cost = Annual heat demand ÷ Boiler efficiency × Gas unit price. A boiler with 88% efficiency delivering 12,000 kWh of heat per year consumes approximately 13,636 kWh of gas.
Heat pump annual electricity cost = Annual heat demand ÷ Seasonal COP × Electricity unit price. A heat pump with a seasonal COP of 3.0 delivering 12,000 kWh of heat consumes 4,000 kWh of electricity.
Standing charges are added separately. The gas standing charge is included in the full gas boiler cost. When a household already pays an electricity standing charge (which is common), switching from gas to a heat pump removes the gas standing charge as an ongoing cost.
Understanding seasonal COP
The Coefficient of Performance (COP) is the ratio of heat output to electrical input. A COP of 3.0 means the heat pump delivers 3 kWh of heat for every 1 kWh of electricity consumed. The seasonal COP (SCOP) averages performance across a full heating season, including cold weather when efficiency drops.
Modern air-source heat pumps have SCOPs typically ranging from 2.5 to 3.5 in UK climates. Ground-source heat pumps have higher SCOPs of 3.5 to 4.5 due to more stable ground temperatures. The higher the SCOP, the lower the running cost.
Break-even electricity price
Because electricity is more expensive per kWh than gas, the heat pump running cost advantage depends on the electricity-to-gas price ratio. The break-even electricity price is the rate at which the heat pump annual cost equals the gas boiler annual cost.
If your electricity price is below the break-even price, the heat pump is cheaper to run. If it is above, the gas boiler is cheaper despite using more fuel. This is why tariffs like Octopus Cosy or Economy 7 can make heat pumps more competitive for homes that can time their heating load.
The sensitivity table is equally useful because SCOP is not fixed in real life. If the installed system performs closer to 2.5 than 3.5, the annual running-cost picture can change sharply even with the same tariff.
Why keeping the gas connection changes the answer
One of the most common comparison mistakes is to remove the gas boiler from the fuel-consumption side of the calculation but forget to ask whether the home still pays the gas standing charge after the switch. If the gas supply stays live for a hob, fireplace, or backup appliance, that standing charge may continue and reduce the heat-pump saving materially.
That is why the live calculator now separates fuel spend from standing charges. A full switch away from gas can make the heat pump look meaningfully better because the gas standing charge disappears. A partial switch can look much closer to cost-neutral because the home still pays for the gas connection even though space heating has moved to electricity.
Required SCOP to beat gas at your current tariff
Users often know their electricity and gas rates but do not know how to translate those into a realistic heat-pump performance target. The useful question is not just whether a brochure mentions COP 4.5 in a test condition. It is what seasonal COP the installed system needs in your home to match or beat the current gas-boiler running cost.
The calculator therefore shows a required SCOP threshold. If your expected installed SCOP is above that figure, the heat pump should beat gas on running cost under the entered assumptions. If the expected SCOP is below it, the gas boiler remains cheaper unless tariff conditions improve or heat demand falls.
How to estimate annual heat demand before you have a heat pump
Many households do not know their annual heat demand in kWh, but they often do know their gas usage, EPC estimate, or installer room-by-room design figure. A practical first pass is to start from the annual kWh used for space heating and hot water rather than total household energy spend. If you only have gas use, remember that cooking can consume a small share as well, so heating demand is usually lower than the total annual gas figure.
This matters because annual heat demand drives both sides of the comparison. A poorly estimated demand figure can make the gas boiler and heat pump both look artificially cheap or expensive. If you have a design proposal from an installer, use the delivered-heat requirement from that proposal rather than guessing from bill cost alone.
Tariffs, flow temperature, and why two heat pumps can have very different running costs
Competitor pages are right to stress that tariff choice can matter almost as much as the machine itself. A standard electricity tariff can leave a heat pump close to cost-neutral with gas, while a specialist heat-pump tariff can widen the saving meaningfully. That is why the break-even electricity price output is useful: it shows how far your current tariff is from cost parity.
Installation quality and flow temperature matter just as much. A well-designed low-flow system with the right emitters can produce a much stronger seasonal COP than a poorly set up system forced to run hot. The calculator cannot judge design quality directly, but the required-SCOP and sensitivity outputs make it easier to see whether your economics rely on a very strong installation or just a broadly competent one.
Worked example: 12,000 kWh heat demand at SCOP 3.0
With annual heat demand of 12,000 kWh, gas at 5.74p/kWh, electricity at 24.67p/kWh, an 88% boiler, and a heat pump SCOP of 3.0, the gas boiler uses about 13,636 kWh of gas while the heat pump uses about 4,000 kWh of electricity. Under those assumptions the heat pump is slightly more expensive to run over the year unless a cheaper electricity tariff or a higher real SCOP changes the balance.
That is why the SCOP sensitivity rows and required-SCOP threshold matter. At a lower seasonal COP the heat pump becomes materially more expensive than gas, while at a stronger SCOP or a better tariff the annual saving becomes clearer. The comparison sheet is useful because it shows both the selected result and how performance drift affects the economics.
Frequently asked questions
Is a heat pump cheaper to run than a gas boiler?
Not always. At recent UK capped tariffs, a heat pump with a seasonal COP around 3.0 can still be slightly more expensive to run than a modern gas boiler, while a higher-performing system or a specialist heat-pump tariff can move the result back in the heat pump’s favour. That is why the calculator shows both the break-even electricity price and the SCOP needed to match gas.
What is a typical annual heat demand for a UK home?
The UK average annual heat demand (space heating and hot water) for a semi-detached house is approximately 12,000–15,000 kWh. A well-insulated modern home may need only 6,000–8,000 kWh, while an older poorly insulated property may need 20,000 kWh or more.
Does insulation matter before installing a heat pump?
Yes — heat pumps operate most efficiently at lower flow temperatures (35–45 °C) compared with gas boilers (60–80 °C). Lower flow temperatures require larger radiators or underfloor heating and a well-insulated home to deliver comfortable room temperatures. Improving insulation reduces annual heat demand and increases heat pump efficiency.
Why does the calculator show different results at different SCOP values?
Because SCOP determines how much electricity the heat pump needs to deliver the same amount of heat. A lower SCOP means more electricity use and a higher running cost, while a higher SCOP means less electricity use and a lower running cost.
Should I keep the gas standing charge in the comparison?
Keep it only if the property will still pay for a live gas connection after the heat pump is installed. If the gas meter is removed and the property no longer uses gas, the gas standing charge can usually be treated as a saving. If the gas supply stays live for cooking, a fire, or backup heat, leaving that standing charge in the comparison is more realistic.
What SCOP usually makes a heat pump cheaper than gas?
There is no single universal number because the answer depends on gas price, electricity price, boiler efficiency, and whether the gas standing charge disappears after the switch. In many UK comparisons the answer sits somewhere around the high-2s to low-3s, but the calculator is more useful than a rule of thumb because it solves the break-even SCOP for your entered tariff assumptions.
How can I estimate annual heat demand if I only have bills?
Start with the annual kWh used for heating and hot water rather than total household spend. EPC estimates, installer heat-loss calculations, or heating-only gas usage are usually better starting points than using total bill cost. If your gas figure includes cooking, the delivered heating demand will usually be somewhat lower than the full annual gas kWh.
Do heat-pump tariffs make a big difference?
They can. Because electricity is much more expensive per kWh than gas, a cheaper electricity tariff can move the heat pump from roughly cost-neutral to clearly cheaper. That is why the break-even electricity price is useful: it shows how close your current rate is to the point where the heat pump matches gas.
What SCOP should I use if I do not know my installed system performance?
A reasonable starting point is the middle of the range used by many current air-source systems, then compare the result across a few SCOP values to see how sensitive the running cost is. The calculator’s sensitivity rows are useful because they show whether the answer changes a little or a lot when performance shifts.
Does this calculator include installation cost or grants?
No. It compares annual running costs only. Installation cost, maintenance, radiator upgrades, hot-water cylinder changes, and grants or incentives can materially change the full project economics, so those should be checked separately.
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