Whether a heat pump is cheaper to run than a gas boiler comes down to one sum: the price of each unit of energy divided by how efficiently the appliance turns it into heat. At the October 2026 price cap, electricity costs 26.32p per kWh and gas 7.97p per kWh, so electricity is about 3.3 times dearer (Ofgem, 2026). A heat pump only wins when its efficiency more than closes that gap.
This comparison works through the real 2026 numbers for a UK home: the cost of useful heat from each system at the current cap, how the seasonal efficiency figure swings the result, and how a dedicated heat pump tariff changes the picture entirely. The angle is installer-first, because the honest answer, that it depends on the design and the tariff, is exactly what a customer needs to hear before they sign.
Key Takeaways
- At the October 2026 cap, electricity is 26.32p per kWh and gas 7.97p per kWh, making electricity about 3.3 times more expensive (Ofgem, 2026).
- A gas boiler at 90 percent efficiency delivers useful heat at about 8.9p per kWh; a heat pump matches that only at a seasonal factor of about 3.0 and beats it clearly at 3.5 or higher.
- Real-world field data put many heat pumps near a seasonal factor of 2.8 to 2.9, so a poorly designed system can cost more to run than gas (Energy Systems Catapult, 2024).
- A dedicated heat pump tariff such as Cosy Octopus offered off-peak power near 14.53p per kWh, which pushes the cost of heat well below gas (Energy Stats, 2026).
- The 7,500 pound Boiler Upgrade Scheme grant narrows the upfront gap, with over 77,500 vouchers already redeemed (GOV.UK, 2026).
Are heat pumps cheaper to run than gas boilers?
Sometimes, and the honest answer depends on efficiency and tariff. On the standard October 2026 price cap, a well-designed heat pump running at a seasonal factor of 3.5 delivers heat at about 7.5p per kWh against roughly 8.9p for a gas boiler, so it is cheaper (Ofgem, 2026). A poorly set-up unit at 2.5 costs more.
This is why blanket claims in either direction mislead customers. The heat pump is not automatically cheaper because it is efficient, nor automatically dearer because electricity costs more per unit. The design, the flow temperature and the tariff decide the outcome, and all three are within the installer's control. That is the real message to carry into a quote conversation.
Heat pump vs gas boiler running cost at the 2026 price cap
The fair way to compare is the cost of one kilowatt hour of useful heat delivered into the home, not the raw fuel price. Dividing the October 2026 cap rates by each appliance's efficiency gives the figures below, all at the standard cap before any special tariff (Ofgem, 2026).
- Gas boiler at 90 percent efficiency: about 8.9p per kWh of useful heat (7.97p gas divided by 0.90).
- Heat pump at seasonal factor 2.5: about 10.5p per kWh, more expensive than gas.
- Heat pump at seasonal factor 3.0: about 8.8p per kWh, roughly level with gas.
- Heat pump at seasonal factor 3.5: about 7.5p per kWh, around 16 percent cheaper than gas.
- Heat pump at seasonal factor 4.0: about 6.6p per kWh, comfortably cheaper than gas.
The crossover point is a seasonal factor of roughly 3.0. Below it the heat pump loses to gas on running cost at the standard cap; above it the heat pump wins, and the margin widens quickly. Because the whole comparison pivots on that one number, the efficiency of the install is not a technical footnote, it is the entire commercial case. A single degree of design flow temperature saved can move the annual bill by a noticeable amount over a heating season.
How much does efficiency change the running cost?
Efficiency is the single biggest lever, and it is where installs go wrong. Field monitoring in the Electrification of Heat project found real-world heat pumps clustered near a seasonal factor of 2.8 to 2.94, well short of the 4.0-plus lab figures manufacturers advertise (Energy Systems Catapult, 2024). A unit stuck at 2.8 barely beats gas.
The gap between a 2.8 and a 3.8 seasonal factor is the difference between a system that disappoints and one that clearly saves money. It is driven by design flow temperature, emitter sizing, weather compensation and commissioning, not by the badge on the box. Getting radiators right so the pump can run at a low flow temperature is the highest-impact decision on the job. Our radiator sizing for heat pumps and SCOP and MCS 031 guides cover how to protect that number.
Does a heat pump tariff make it cheaper?
Yes, and this is where the comparison tilts decisively toward the heat pump. Dedicated heat pump tariffs price electricity far below the standard cap during off-peak windows: Cosy Octopus, for instance, offered off-peak power near 14.53p per kWh (Energy Stats, 2026). At a seasonal factor of 3.5 that is barely 4p per kWh of useful heat.
The practical model is to shift the bulk of heating and hot water into those cheaper windows, often with a buffer or the building fabric storing heat across the peak. A customer on the right tariff with a decent seasonal factor can run heating for meaningfully less than a gas boiler, even though gas looks cheaper per raw unit. Our heat pump tariff guide compares the current options.
What about standing charges and upfront cost?
Standing charges and capital cost matter alongside the unit rate. Every electricity account carries a daily standing charge, 54.83p a day at the October 2026 cap, and removing the gas meter altogether saves the separate gas standing charge, which improves the heat pump case for a fully electric home (Ofgem, 2026).
Upfront, a heat pump still costs more than a boiler swap, but the Boiler Upgrade Scheme takes 7,500 pounds off an air source install and has already paid out on more than 77,500 vouchers (GOV.UK, 2026). For homes coming off oil or LPG, the grant rose to 9,000 pounds from 21 July 2026, and those households often see the largest running-cost saving of all. See our heat pump grants for oil boiler replacement guide.
Which homes see the biggest running cost saving?
The biggest savings land where the alternative fuel is expensive or the home suits a low flow temperature. Homes currently on oil, LPG or direct electric heating almost always cut running costs with a heat pump, because those fuels cost far more per unit of heat than mains gas does. Independent analysis has put the saving for oil-heated homes switching to a heat pump at over 650 pounds a year (Nesta, 2026). A well-insulated home with generously sized emitters compounds the win.
By contrast, a poorly insulated home on cheap mains gas, fitted with small radiators forcing a high flow temperature, is the hardest case, and may see little or no running-cost saving without fabric and emitter work first. Identifying which category a property falls into at survey stage is what lets you set an honest expectation rather than overpromise. See our air source heat pump cost breakdown for the capital side.
Payback and lifetime cost
Running cost is only half the lifetime picture; replacement cycles matter too. A gas boiler typically lasts around 10 to 15 years while a heat pump is generally expected to last 20 years or more with servicing (Energy Saving Trust, 2026). Over two decades the heat pump usually avoids at least one full boiler replacement, and that deferred capital cost belongs in any fair lifetime comparison, not just the annual bill.
For a customer, the sensible framing is total cost over the appliance's life: grant-adjusted purchase price, annual running cost at a realistic seasonal factor and tariff, and avoided replacements. Presented that way, a well-designed heat pump on a heat pump tariff is competitive to clearly cheaper over its life, while a poorly designed one on the standard cap is not. The design is the deciding variable.
Heat pump vs gas boiler: the installer's takeaway
The comparison rewards installers who design for a low flow temperature and steer customers onto the right tariff, and punishes those who drop a unit in without either. At the 2026 cap, aim for a seasonal factor above 3.0 as the floor and 3.5-plus as the target, then add a heat pump tariff to open a clear margin over gas.
Sell the sum, not the slogan. Show the customer the cost of useful heat at their likely seasonal factor and tariff, next to their current gas cost, and let the numbers carry the decision. Reonic's design and proposal tools let installers model the flow temperature, seasonal factor and tariff assumptions in one place so the running-cost promise in the quote matches what the system will actually deliver.
Is a heat pump cheaper to run than a gas boiler in 2026?
It can be, but not automatically. At the October 2026 cap, electricity is 26.32p per kWh against 7.97p for gas, so a heat pump only wins on running cost at a seasonal factor around 3.0 or higher, or on a dedicated heat pump tariff (Ofgem, 2026). A poorly designed system can cost more than gas.
How much does it cost to run a heat pump per kWh of heat?
At the October 2026 cap, a heat pump at a seasonal factor of 3.5 delivers useful heat at about 7.5p per kWh, against roughly 8.9p for a 90 percent gas boiler (Ofgem, 2026). At 2.5 the heat pump rises to about 10.5p, more than gas, which is why efficiency is decisive.
Why is electricity so much more expensive than gas?
Electricity carries higher wholesale, network and policy costs per unit than gas in the UK. At the October 2026 cap the ratio is about 3.3 to 1 (Ofgem, 2026). A heat pump overcomes this by delivering three or more units of heat per unit of electricity, which a gas boiler cannot do.
Do heat pump tariffs really cut the cost?
Yes, materially. Tariffs such as Cosy Octopus offered off-peak electricity near 14.53p per kWh, roughly half the standard cap rate (Energy Stats, 2026). Shifting heating and hot water into those windows can bring the cost of useful heat well below gas, provided the system and controls are set up to use them.
Will a heat pump save money in a poorly insulated house?
Often not without other work. A poorly insulated home on cheap mains gas with small radiators forces a high flow temperature, which drops the seasonal factor and erodes the saving. In that case, fabric and emitter upgrades come first, or the customer should expect running costs similar to gas rather than a large reduction.
