Is a heat pump actually cheaper to run? The numbers in April 2026
With the Boiler Upgrade Scheme grant now at £7,500 and electricity tariffs built specifically for heat pumps, the calculation has quietly tilted.
Every winter brings a fresh wave of "heat pumps are too expensive to run" arguments. The frustrating answer: it depends entirely on three things — your tariff, your home, and how you actually use it.
The honest running-cost maths
A well-installed air-source heat pump delivering a seasonal coefficient of performance (SCOP) of 3.5 — realistic for a post-2000 home with competent radiators — produces 3.5 kWh of heat per 1 kWh of electricity consumed.
On a flat electricity tariff at 24.5p/kWh, that works out to about 7.0p per kWh of heat. Mains gas sits at 6.04p. Gas still wins.
On a heat-pump tariff (Octopus Cosy, EDF Heat, British Gas EVD) where the off-peak rate is 14.9p and you shift 70% of your heating into the cheap window, the effective cost drops to about 5.3p per kWh of heat. Now gas loses.
What still makes it a bad deal
- A poorly sized system running continuously at low flow temperatures with no cylinder buffer.
- A home with no loft insulation and single glazing.
- Staying on a flat-rate "variable standard" tariff after installation.
What tipped the scales
- The Boiler Upgrade Scheme grant rose to £7,500 last autumn, shaving install costs meaningfully.
- Smart tariffs have matured — three big suppliers now offer heat-pump-specific deals with multiple cheap windows a day.
- Hot-water cylinders are back, and a 200L cylinder makes time-shifting almost trivial.
If your gas boiler is 12+ years old and you're replacing the hot water cylinder anyway, sit down with a spreadsheet before ordering another combi.
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