Heat pump or gas boiler at this winter's price cap: our own break-even calculation, 2026-10-30

The one number that decides it

A heat pump turns 1 kWh of electricity into SPF kWh of heat (SPF = seasonal performance factor, measured over a year in a real home). A gas boiler turns 1 kWh of gas into (efficiency) kWh of heat. Per kWh of heat:

• heat pump cost = electricity unit rate / SPF
• boiler cost = gas unit rate / boiler efficiency

So a heat pump is cheaper per kWh of heat when SPF > (electricity rate / gas rate) x boiler efficiency. That ratio is the whole story, and it moved this quarter.

The prices (Ofgem price cap, Direct Debit, average for England, Scotland and Wales)

Source [Ofgem, "Energy price cap unit rates and standing charges", https://www.ofgem.gov.uk/your-energy-supply/your-energy-bill/energy-price-cap-unit-rates-and-standing-charges, read 2026-10-30]:

• 1 October to 31 December 2026: electricity 26.32p per kWh, standing charge 54.83p a day; gas 7.97p per kWh, standing charge 29.68p a day.
• 1 July to 30 September 2026: electricity 26.11p per kWh, 57.19p a day; gas 7.33p per kWh, 29.04p a day.
• Ofgem: "There is no VAT on electricity from 1 October 2026 to 31 March 2027." Gas figures include 5% VAT.
• Ofgem: the cap for a typical household is £1,723 a year from 1 October 2026, up 4% on the previous period.

Our calculation (every figure below is ours, from the prices above)

Electricity / gas price ratio: 26.32 / 7.97 = 3.302 this quarter (last quarter 26.11 / 7.33 = 3.562). Break-even SPF (the heat pump efficiency needed just to match the boiler per kWh of heat):

| Boiler efficiency | Jul-Sep 2026 | Oct-Dec 2026 | | 84% | 2.99 | 2.77 | | 90% | 3.21 | 2.97 | The 84% is the "typical fossil fuel heating system efficiency" the Heat Pump Association cites from a DESNZ impact assessment [HPA, 19 December 2024, https://hpauk.org.uk/?p=273]. The 90% is our example of a modern condensing boiler running well (an assumption, label it).

What real heat pumps achieve

Energy Systems Catapult's Electrification of Heat demonstration (742 heat pumps in British homes, monitored November 2020 to August 2022): "The median SPF observed in ASHP systems during the EoH Demonstration Project was 2.80 (280%)." [Energy Systems Catapult, 16 March 2023, https://es.catapult.org.uk/news/heat-pumps-shown-to-be-three-times-more-efficient-than-gas-boilers/] The later report (HPA, 19 December 2024) gives an average of 293% for the sampled air source heat pumps and says the median improved by over 10% on earlier installations; it gives no new median figure, so we use 2.80.

Per kWh of heat, this quarter

• Heat pump at the median SPF 2.80: 26.32 / 2.80 = 9.40p.
• Gas boiler at 84%: 7.97 / 0.84 = 9.49p. At 90%: 7.97 / 0.90 = 8.86p.

So against a typical 84% system the median heat pump is already slightly cheaper per kWh of heat; against a 90% boiler it is 0.54p dearer.

The standing charge flips it for most homes

A home that goes all-electric stops paying the gas standing charge: 29.68p x 365 = £108.33 a year this quarter (£106.00 last quarter). Worked example, 10,000 kWh of heat a year (an example figure, not an average; a reader's own bill shows their gas kWh, and heat = gas kWh x boiler efficiency):

| Heat pump SPF | vs 84% boiler, saves a year | vs 90% boiler, saves a year | | 2.5 | £4.34 | -£58.91 (costs more) | | 2.8 (median) | £117.14 | £53.89 | | 3.0 | £179.81 | £116.55 | | 3.5 | £305.14 | £241.89 | Check, SPF 2.8 vs 90%: boiler 10,000 x 8.8556p = £885.56, plus £108.33 standing = £993.89; heat pump 10,000 x 9.40p = £940.00; difference £53.89. Second way: 10,000 x (8.8556 - 9.4000)p = -£54.44 on units, + £108.33 standing = £53.89. Same. The heat demand where a median heat pump stops beating a 90% boiler: £108.33 / 0.5444p per kWh = about 19,900 kWh of heat a year this quarter. Last quarter the same sum gave about 9,000 kWh (the unit gap was 1.181p). So with this quarter's prices, a median heat pump runs cheaper than even a good boiler in any home using less than about 19,900 kWh of heat a year, once gas is disconnected.

What this cannot tell you

• Running cost only: the installed price, the Boiler Upgrade Scheme grant, and replacement timing are left out.
• Single-rate tariffs only: heat pump tariffs with cheaper off-peak hours lower the heat pump's cost further; we did not model them.
• SPF varies a lot between homes (Catapult notes performance variation remains high); a poorly set-up system at 2.3 would lose.
• Regional rates and standing charges differ from the GB average; the formula holds with a reader's own rates.
• Prices change every three months; the 1 January 2027 cap will move the break-even again.
• Cooking on gas keeps the standing charge, and the standing-charge saving disappears.

Voice notes for the writer

• Lead with the answer: at this winter's cap, a heat pump at the median real-world efficiency (2.80) costs less to run than a gas boiler in most homes, once the gas standing charge goes.
• A guess fits: "How efficient does a heat pump need to be to beat a gas boiler this winter?" (most guess 3 or 4; the answer is 2.77 vs a typical boiler).
• The simulation block fits: inputs electricity rate, gas rate, SPF, boiler efficiency, heat demand, gas standing charge; results cost per kWh of heat each way, yearly saving, break-even SPF.
• UK (Great Britain) prices only; say so. Cite Ofgem for prices, Catapult for SPF 2.80, HPA for 84%; our calculation for the rest; 90% and 10,000 kWh are labelled examples.