TL;DR:
- Air source heat pumps cost £8,000–£15,000 installed; the UK Boiler Upgrade Scheme grants £7,500, cutting your net cost to as low as £500–£2,500
- Gas is still marginally cheaper to run in the UK in 2026 — but a heat pump at COP 3.5+ matches gas running costs, and adding solar tips it firmly in the heat pump’s favour
- Never accept a quote without a room-by-room heat loss calculation — it’s the only reliable way to size the system correctly
A heat pump installed in the wrong home costs more to run than the boiler it replaced. Installed in the right home, it cuts heating bills by 30–50% and runs on electricity that can come from your roof. The difference is preparation — and knowing what questions to ask.
How a Heat Pump Works
A heat pump doesn’t generate heat — it moves it. That distinction matters financially.
A gas boiler burns fuel to create heat, capped at roughly 90–95% efficiency. A heat pump extracts warmth from outdoor air (or the ground) and moves it inside. The ratio of heat delivered to electricity consumed is the Coefficient of Performance (COP).
Air source heat pumps achieve COP 2.5–4.5. Ground source heat pumps achieve COP 3.0–5.0 year-round. In plain terms: 1kWh of electricity in, 3–4kWh of heat out. COP drops in cold weather, but modern cold-climate models from Mitsubishi, Daikin, and Vaillant maintain COP above 1.8 down to −20°C — well below anything the UK normally experiences.
Air Source vs Ground Source
Air source (ASHP): UK installed cost £8,000–£15,000. COP 2.5–4.0. External unit on a wall or ground-mounted, permitted development in most UK locations without planning permission.
Ground source (GSHP): UK installed cost £15,000–£35,000+. COP 3.5–5.0 year-round because the ground stays at a stable 8–12°C. Requires 100–200m² of trench per 8kW or an 80–120m borehole.
For most UK homeowners, the extra £10,000–£15,000 for a ground source rarely pays back through the COP advantage given the UK’s mild climate. Air source is the right starting point unless you have specific reasons for ground source — plenty of land, or an existing borehole.
UK Climate Suitability
The UK is actually one of the better climates for heat pumps. January averages of 3–5°C are well within ASHP operating range. Sweden and Norway run heat pumps in far harsher winters — 60% of Swedish homes already use them. The UK’s damp, mild climate is close to ideal.
The challenge in the UK isn’t the climate — it’s the 4:1 electricity-to-gas price ratio. Until that narrows, or until you add solar, the running cost comparison is tighter than in countries where electricity is cheaper relative to gas.
Two Non-Negotiables Before You Install
Heat pumps deliver water at 35–55°C versus a gas boiler’s 65–80°C. Two things follow from this.
1. Insulate first. You need 270mm loft insulation minimum, cavity wall insulation where accessible, and double glazing throughout. At 45°C flow temperature, a leaky home loses heat faster than the pump can replace it.
2. Upgrade your emitters. Standard radiators underperform at 45°C. Options:
- K2 radiators (double-panel, double-convector): roughly twice the output; full house £2,000–£4,000
- Underfloor heating (UFH): runs at 35–40°C — the ideal emitter for heat pumps
Old undersized radiators plus minimal insulation plus a heat pump is the combination most likely to fail. It’s a context problem, not a technology problem.
Sizing: Get It Right
An oversized heat pump short-cycles, reducing seasonal COP by 15–25% and accelerating compressor wear. The correct method is a room-by-room heat loss calculation to BS EN 12831.
Rough guide for a well-insulated UK home: 6–8kW for a 1960s–80s semi, 4–6kW for a modern 3-bed detached, 10–14kW for a large Victorian. Decline any quote that doesn’t come with a heat loss calculation. If an installer is guessing at the size, find someone else.
Real Running Costs
UK: 3-bed semi, post-insulation upgrade (12,000kWh annual heat demand)
- ASHP at seasonal COP 3.0: 4,000kWh × £0.24 = £960/year
- Gas boiler at 90%: 13,333kWh × £0.06 = £800/year
Gas comes out about £160/year cheaper due to the price ratio. At COP 3.5 the heat pump matches gas (£823/year); at COP 4.0 it beats it (£720/year). Target SCOP 3.5+ — get your installer to commit to this in writing, with proper insulation and emitter upgrades as the conditions.
Add solar and the calculation shifts decisively in the heat pump’s favour. Running a heat pump partly on free solar electricity is a very different proposition to paying 24p/kWh for everything.
Grants and Incentives
The Boiler Upgrade Scheme (BUS) offers £7,500 for air source or ground source heat pumps in England and Wales. Your installer must be MCS-certified; the grant is deducted from your invoice; there’s no income limit. In Scotland, the equivalent is the Home Energy Scotland scheme.
The grant effectively means an ASHP costing £12,000 to install becomes £4,500 net. That’s a significant difference.
7 Questions to Ask Every Installer
- “Can you show me the heat loss calculation?” — No calculation means guessing at size. Walk away.
- “What seasonal COP are you targeting?” — Get a commitment to SCOP 3.0–3.5+ with a verification method.
- “Is emitter upgrade included in the quote?” — Often quoted separately. Get the full installed cost.
- “Are you MCS-certified?” — Required for the BUS grant.
- “What is the warranty, and what voids it?” — Major brands offer 5–10 years.
- “What noise level should I expect?” — UK permitted development requires below 42 dB(A) at a neighbour’s window.
- “What does commissioning involve?” — Flow rate balancing and a monitored test run are non-negotiable.
A heat pump is the right choice for most homes in 2026 — with preparation. Insulate first, size correctly, and specify adequate emitters. The £7,500 BUS grant makes the financial case compelling despite the electricity-to-gas price ratio. Target SCOP 3.5+, add solar if you can, and don’t sign a quote without a heat loss calculation.