What is the payback range with the BUS grant?

Against the three published post-grant prices (Octopus £4,064, E.ON Next from £4,946, Aira £6,729), running-cost savings alone take about sixteen years at the most favourable combination in the published evidence, forty to sixty-seven years at the trial's median SPF, and never break even where the delivered SPF lands in the bottom quartile against an efficient boiler. Payback is the wrong frame for this decision at this cap. The grant is worth £7,500 on day one, which no fuel-bill saving at these rates will match.

Where does it not pay back?

Where the delivered SPF falls below about 2.6, which the Electrification of Heat trial found in roughly a quarter of real installations rather than only in edge cases. Where the boiler being replaced is a good modern condensing unit at 90% or better, which narrows the gap to nothing. Where fabric has not been addressed first, so the flow temperature has to be raised and the SPF falls with it. And where the house keeps its gas supply for cooking, because then the £108.33 standing charge that does most of the work in the sum above is still being paid.

What questions to ask the installer?

Heat-loss calculation method (Heat-Geek-style MCS plus room-by-room vs whole-house EPC-derived), flow temperature design (40 to 45°C target for a SCOP above 3.0), radiator sizing margin, weather-comp curve plan, and delivered-SCOP commitment with a 12-month follow-up review.

Working file Q3

Is a heat pump worth it in 2026

The fuel bill barely moves at this cap. The grant is the case.

Direct answer

At the Ofgem cap for 1 October to 31 December 2026 (gas 7.97p, electricity 26.32p) a gas boiler at 85% seasonal efficiency delivers heat at 9.38p per kWh and an air-source heat pump at the national trial's median delivered SPF of 2.78 delivers it at 9.47p. They are the same number for practical purposes, so the fuel bill barely moves. What moves is the standing charge: a house off gas stops paying 29.68p a day, which is £108.33 a year. The case for a heat pump in 2026 is the £7,500 Boiler Upgrade Scheme grant, the carbon delta and a heat-pump tariff. It is not an immediate running-cost saving, and anyone selling it as one is not showing you the arithmetic.

Further questions

What is the payback range with the BUS grant?: Against the three published post-grant prices (Octopus £4,064, E.ON Next from £4,946, Aira £6,729), running-cost savings alone take about sixteen years at the most favourable combination in the published evidence, forty to sixty-seven years at the trial's median SPF, and never break even where the delivered SPF lands in the bottom quartile against an efficient boiler. Payback is the wrong frame for this decision at this cap. The grant is worth £7,500 on day one, which no fuel-bill saving at these rates will match.
Where does it not pay back?: Where the delivered SPF falls below about 2.6, which the Electrification of Heat trial found in roughly a quarter of real installations rather than only in edge cases. Where the boiler being replaced is a good modern condensing unit at 90% or better, which narrows the gap to nothing. Where fabric has not been addressed first, so the flow temperature has to be raised and the SPF falls with it. And where the house keeps its gas supply for cooking, because then the £108.33 standing charge that does most of the work in the sum above is still being paid.
What questions to ask the installer?: Heat-loss calculation method (Heat-Geek-style MCS plus room-by-room vs whole-house EPC-derived), flow temperature design (40 to 45°C target for a SCOP above 3.0), radiator sizing margin, weather-comp curve plan, and delivered-SCOP commitment with a 12-month follow-up review.

Surveyed 1 October 2026. Ofgem cap for 1 October to 31 December 2026 applied (gas 7.97p, elec 26.32p, gas standing 29.68p, elec standing 54.83p). Next scheduled review 25 November 2026 (January cap announcement). [ref Q3]

By Oliver Wakefield-Smith, Founder, Digital Signet. Corrections to oliver at digitalsignet dot com.