Heat pumps are no longer a niche technology reserved for eco-pioneers. With the government's Boiler Upgrade Scheme offering grants of up to £7,500 and gas boilers being phased out of new builds, an increasing number of UK homeowners are weighing up whether a heat pump makes financial sense. This guide breaks down the full cost picture — upfront installation, running costs, available grants, and crucially, when a heat pump will and won't work well in your home.
Air Source vs Ground Source Heat Pumps: Upfront Cost Comparison
There are two main types of heat pump available to UK homeowners: air source heat pumps (ASHP) and ground source heat pumps (GSHP). Both extract renewable heat from the environment, but they differ significantly in cost and installation complexity.
| Type | Typical Installed Cost (before grant) | Boiler Upgrade Scheme Grant | Net Cost After Grant |
|---|---|---|---|
| Air Source Heat Pump (ASHP) | £8,000–£15,000 | £7,500 | £500–£7,500 |
| Ground Source Heat Pump (GSHP) | £15,000–£35,000 | £7,500 | £7,500–£27,500 |
| Gas Boiler (replacement, for comparison) | £2,000–£4,500 | None | £2,000–£4,500 |
ASHP units are mounted externally (similar to an air conditioning unit) and draw heat from outdoor air, even in temperatures as low as -15°C. They are considerably cheaper to install and are the more common choice for domestic retrofits. GSHP systems require ground loops buried in your garden (either horizontally across a large area or vertically via boreholes), making them significantly more disruptive and expensive — but they operate at a higher efficiency year-round.
Understanding COP: Why Efficiency Matters More Than Fuel Cost Alone
The key performance metric for heat pumps is the Coefficient of Performance (COP) — the ratio of heat output to electricity consumed. A COP of 3.0 means the system produces 3 kWh of heat for every 1 kWh of electricity used.
- ASHP typical COP: 2.5–4.0 (varies with outdoor temperature; lower on cold days)
- GSHP typical COP: 3.5–5.0 (more stable because ground temperature varies less)
Because heat pumps run on electricity rather than gas, the economics depend heavily on the relative price of electricity versus gas. At current typical UK unit rates (electricity ~28p/kWh, gas ~6p/kWh), a heat pump needs a COP above approximately 4.5 to match a gas boiler's running cost per unit of heat delivered. Most ASHPs don't consistently achieve this in a poorly insulated home — but in a well-insulated property with underfloor heating, the numbers improve considerably.
Running Costs: Heat Pump vs Gas Boiler
| Heating System | Annual Running Cost (3-bed semi, EPC C) | Notes |
|---|---|---|
| Modern gas combi boiler (90%+ efficiency) | £1,100–£1,500 | At ~6p/kWh gas |
| ASHP (COP 3.0, poorly insulated home) | £1,400–£2,000 | Higher consumption |
| ASHP (COP 3.5, well-insulated home) | £900–£1,300 | Competitive with gas |
| GSHP (COP 4.0–4.5) | £700–£1,100 | Best-case running costs |
The headline message: a heat pump in a draughty, poorly insulated Victorian terrace will almost certainly cost more to run than a gas boiler. In a well-insulated modern home — or one that has had loft, wall, and floor insulation upgraded beforehand — the picture changes substantially.
The Boiler Upgrade Scheme: How to Claim Your £7,500 Grant
The Boiler Upgrade Scheme (BUS), administered by Ofgem, offers:
- £7,500 for an air source heat pump
- £7,500 for a ground source heat pump
To be eligible, you must:
- Own the property (or have landlord permission)
- Have a valid Energy Performance Certificate (EPC) with no outstanding loft or cavity wall insulation recommendations
- Use an MCS-certified installer — the Microgeneration Certification Scheme is the government-endorsed quality standard; only MCS installers can apply for BUS vouchers on your behalf
The voucher is applied by your installer at point of sale — you never handle the money directly. Vouchers are valid for three months. Check eligibility and find certified installers at the MCS website or via the Ofgem BUS portal.
When a Heat Pump Works Well — and When It Doesn't
A heat pump is not a like-for-like replacement for a gas boiler. It operates most efficiently at lower flow temperatures (35–45°C versus a gas boiler's 65–80°C), which means:
Heat pumps work best when:
- Your home has good insulation (EPC B or C minimum)
- You have underfloor heating (UFH) — large surface area, low flow temperature ideal
- You have oversized radiators (at least 25–50% larger than standard to compensate for lower flow temps)
- You are building new or doing a major retrofit
Heat pumps struggle when:
- Your home is poorly insulated (EPC E, F, G)
- You have standard-sized radiators throughout
- Your home is very old with solid walls and no insulation upgrade planned
- You have a small garden and can't afford GSHP borehole costs
The general rule of thumb from the Heat Pump Association is that homes should achieve a heat loss below 100W/m² before a heat pump retrofit makes strong economic sense.
Planning Permission for Heat Pumps
In England, most ASHP installations fall under Permitted Development (PD) rights, meaning no planning application is required — provided the unit is not on a wall or roof facing a highway, is not in a conservation area or listed building, and noise limits are met (42 dB(A) at one metre from a neighbour's window).
GSHP systems generally require planning permission in England due to ground excavation. Always check with your local planning authority, and use the Planning Portal to confirm PD rules for your specific situation.
Payback Period and Low-Income Options
For most ASHP installations (after the £7,500 BUS grant), payback periods typically run 10–14 years, improving as electricity prices fall relative to gas over time.
For low-income households, the ECO4 scheme (Energy Company Obligation) may fund heat pump installation at no cost, alongside insulation measures. Eligibility is based on income, benefits received, and property EPC rating. Contact your energy supplier or check the government's ECO4 guidance for current criteria.
Plan Your Heat Pump Upgrade with Renovate Me
Switching to a heat pump involves more than just swapping out the boiler — it often requires insulation upgrades, radiator changes, and hot water cylinder installation. Renovate Me breaks your entire renovation into a clear, sequenced roadmap so you know exactly what to do, in what order, and at what cost.