Electricity costs three to four times more than gas per unit. Heat pumps run on electricity. So how can a heat pump possibly be cheaper to run than a gas boiler? This is the most common, and most reasonable, question we get asked, so here's the maths in full, with nothing hidden.
The one number that decides everything
A gas boiler turns 1kWh of gas into about 0.9kWh of heat, roughly 90% efficient. A heat pump doesn't make heat from electricity; it moves heat from the outside air into your home. That's why it can turn 1kWh of electricity into 3–4kWh of heat. That multiplier, averaged across a whole year, is called the SCOP (Seasonal Coefficient of Performance).
So the comparison is really: gas price ÷ 0.9 versus electricity price ÷ SCOP. Using typical 2026 prices , gas around 7p/kWh, electricity around 24.5p/kWh:
| System | Sums | Cost per kWh of heat |
|---|---|---|
| Gas boiler (90%) | 7.0p ÷ 0.90 | 7.8p |
| Heat pump, poorly installed (SCOP 2.5) | 24.5p ÷ 2.5 | 9.8p |
| Heat pump, typical good install (SCOP 3.5) | 24.5p ÷ 3.5 | 7.0p |
| Heat pump, well-designed (SCOP 4.0+) | 24.5p ÷ 4.0 | 6.1p |
| Heat pump on a heat pump tariff (~18p, SCOP 3.5) | 18.0p ÷ 3.5 | 5.1p |
Read that table twice, because it contains the entire honest story: a badly installed heat pump costs more to run than a gas boiler, and a well-designed one costs less, especially on one of the heat-pump electricity tariffs now offered by Octopus and others. The difference between SCOP 2.5 and SCOP 4 isn't the hardware; it's the design: correct sizing, right-sized radiators and a low flow temperature. This is why we bang on about heat loss surveys so much.
A worked example: 3-bed semi in Stafford
Take a typical 3-bed semi using around 12,000kWh of heat per year:
- Gas boiler: 12,000 ÷ 0.9 × 7.0p = ~£930/year (plus ~£110/year gas standing charge, plus the annual service).
- Heat pump at SCOP 3.5, standard tariff: 12,000 ÷ 3.5 × 24.5p = ~£840/year.
- Heat pump at SCOP 3.5, heat pump tariff (~18p): ~£620/year, and if you drop gas entirely, the gas standing charge disappears too.
Against modern gas that's a saving of roughly £200–£400 a year for a well-designed system. Against oil, LPG or electric heating the gap is far bigger, oil and LPG homes routinely save £400–£800 a year, which is why rural Staffordshire is where heat pumps make the fastest financial sense.
The three things that decide whether you save
1. Design quality. The SCOP your system actually achieves is set on day one by the survey and design. Demand to see the heat loss calculation, from us or anyone else.
2. Your current fuel. Replacing oil, LPG or electric heating: clear savings. Replacing efficient mains gas: modest savings with good design, roughly break-even with average design.
3. Your tariff. Heat-pump tariffs (like Cosy Octopus) knock 20–30% off the electricity that feeds your heat pump. We set systems up tariff-ready as standard.
And the bit nobody mentions: the £7,500 head start
Running costs are only half the equation, the other half is that the Boiler Upgrade Scheme currently pays £7,500 of the installation. A like-for-like gas boiler replacement has no grant at all. Factor that in and the total cost-of-ownership comparison over 15 years tilts firmly towards the heat pump for most homes, before counting a single unit of cheaper heat.
Prices used: gas ~7p/kWh, electricity ~24.5p/kWh (typical capped rates, mid-2026), heat pump tariffs ~18p/kWh. Energy prices move, the ratios are what matter, and we'll run your numbers with current prices at your survey. As we publish measured SCOP data from our own installs on our case studies page, you'll be able to check our claims against real Staffordshire homes.
Want your numbers, not averages?
The free survey calculates your home's real heat demand and gives you a running-cost estimate you can hold us to.