Heat Pump Running Costs vs Gas Boiler UK — 2026
Real UK annual running cost data. Standard Ofgem cap, Octopus Cosy, and Octopus Go — across different home types. What drives the gap, why tariff choice matters more than brand, and 15-year cumulative cost.
The honest 2026 running cost picture
Energy prices changed dramatically since 2021. As of October 2025 Ofgem cap:
- Gas: 6.99 p/kWh (+ standing charge ~32p/day)
- Electricity standard: 26.35 p/kWh (+ standing charge ~62p/day)
- Octopus Cosy: blended avg ~19.20 p/kWh with smart scheduling
- Octopus Go: blended avg ~21.50 p/kWh (cheaper overnight)
The maths: heat pumps need SCOP > (electricity ÷ gas) to beat gas on running cost.
- Standard cap: SCOP needed = 26.35 ÷ 6.99 = 3.77 to beat gas
- Octopus Cosy: SCOP needed = 19.20 ÷ 6.99 = 2.75 to beat gas
- Octopus Go: SCOP needed = 21.50 ÷ 6.99 = 3.08 to beat gas
A typical well-installed ASHP achieves SCOP 3.0-3.4. So on Cosy you comfortably beat gas; on standard cap you're roughly break-even; on Go you need a good install.
Annual cost by property type
| Home type | Gas boiler/yr | HP std cap | HP Cosy | HP Go |
|---|---|---|---|---|
| 1-bed flat (50 m²) | £520 | £615 | £450 | £505 |
| 2-bed terrace (70 m²) | £725 | £860 | £625 | £700 |
| 3-bed semi (95 m²) | £985 | £1,170 | £850 | £955 |
| 4-bed detached (140 m²) | £1,450 | £1,720 | £1,255 | £1,405 |
| 5-bed period (200 m²) | £2,080 | £2,455 | £1,790 | £2,005 |
Notice: on standard cap, gas is usually cheaper by ~15-20%. On Cosy, heat pump wins by ~15%. The tariff choice is decisive.
What's the difference between Cosy and Go?
Octopus Cosy is purpose-built for heat pump households. Three cheap windows (early morning, mid-afternoon, late evening) align with heating demand. Peak rate (32.5p) is between 4-7pm — when you should pre-heat the home before.
Octopus Go is cheaper at night (8.5p between midnight-5am) but flat rate the rest of the day. Best for households with EVs that charge overnight + heat pumps with large buffer tanks that can store overnight heat for daytime use.
Why SCOP matters more than brand
Two identical 8 kW Mitsubishi Ecodans installed in similar 3-bed homes can have wildly different running costs:
- Good install (correctly-sized radiators, flow temp 40°C, weather compensation): SCOP 3.4 → £850/year
- Poor install (undersized radiators, flow temp 55°C, manual controls): SCOP 2.4 → £1,200/year
That's £350/year just from install quality. Over 15 years: £5,250 difference. The pump is identical.
Lesson: installer quality matters more than brand selection. Choose installers with 100+ installs and good Trustpilot reviews over chasing the cheapest quote.
What about gas price inflation?
The Office for Budget Responsibility projects:
- UK gas prices: +4-6% per year through 2030
- UK wholesale electricity: -2-3% per year as renewables share grows
By 2030, the gas-to-electricity ratio could improve from 3.77× to ~3.0×, meaning heat pumps with SCOP 3.0+ comfortably beat gas even on standard cap. The trend favours heat pumps over time.
15-year cumulative running cost (3-bed semi)
| Scenario | Year 1 | Year 5 | Year 10 | Year 15 cumulative |
|---|---|---|---|---|
| Gas boiler (constant prices) | £985 | £4,925 | £9,850 | £14,775 |
| HP standard cap | £1,170 | £5,850 | £11,700 | £17,550 |
| HP Octopus Cosy | £850 | £4,250 | £8,500 | £12,750 |
| HP Octopus Cosy + gas inflation +4%/yr | £850 | £3,950 | £7,800 | £11,500 |
The bottom row is the most realistic forward projection: with gas inflation factored in, heat pump on Cosy saves ~£3,275 over 15 years vs gas boiler — on running cost alone, before counting the £7,500 BUS grant.
Tips to minimise your heat pump running cost
- Switch to Octopus Cosy if not already — biggest single saving
- Install a buffer tank (£600-£1,200) — lets you shift load to cheap hours
- Use weather compensation — modulates flow temp to outdoor conditions
- Pre-heat the home before 4-7pm peak window
- Keep flow temperature low (40-45°C) — every 5°C lower = ~10% efficiency gain
- Annual MCS service — clean filters, check refrigerant, verify settings