What Is an Air Source Heat Pump?
An air source heat pump (ASHP) extracts heat from outdoor air — even in freezing conditions — and uses a refrigerant cycle to concentrate it, delivering hot water to your radiators, underfloor heating and taps. Modern R290 (propane) units like the Vaillant aroTHERM Plus we install work down to -22°C and reach flow temperatures up to 75°C, making them a direct replacement for a gas, oil or LPG boiler in virtually any UK home.
For every 1 kWh of electricity consumed, a well-designed heat pump produces 3–4 kWh of heat — that 300–400% efficiency is what makes them cheaper to run than combustion heating, and it is why countries far colder than the UK (Norway, Sweden, Finland) have the highest adoption rates in the world.
A refrigerant loop absorbs low-grade heat from the outside air, compresses it to a useful temperature, releases it into your heating, then resets — continuously, even in freezing weather.
How Much Does a Heat Pump Cost?
A typical air source heat pump installation in the UK costs £11,000–£15,500 before grants, depending on your home's size and complexity. After the £7,500 Boiler Upgrade Scheme grant (or £9,000 for off-gas-grid homes) and 0% VAT, most households pay roughly £4,000–£8,000 for a fully designed system — cylinder, radiator upgrades, electrics and commissioning included.
→ Full cost breakdown with worked examples by home type → Is my heat pump quote fair? A sense-check guide
Illustrative figures for a typical air source heat pump. The £7,500 Boiler Upgrade Scheme grant (up to £9,000 off-gas) and 0% VAT bring the real cost right down — we deduct the grant from your bill.
Grants and Funding
The Boiler Upgrade Scheme (BUS) is the main incentive: £7,500 towards an air source heat pump, rising to £9,000 for off-gas-grid homes (applications 21 July 2026 – 31 March 2027). Installations also attract 0% VAT until 31 March 2027. Lower-income households may qualify for the Warm Homes: Local Grant (up to £15,000) or ECO4 (to 31 December 2026).
→ BUS grant explained: eligibility, amounts, how to apply → The £9,000 off-gas-grid grant — who qualifies → All solar panel grants available in 2026
Running Costs: Heat Pump vs Gas, Oil and LPG
A well-designed heat pump achieves a Seasonal COP (SCOP) of 3.5–4.0, delivering heat at roughly 6–7p per kWh — cheaper than gas (~7.8p), far cheaper than oil or LPG. On a smart heat-pump tariff with cheap off-peak windows, the effective cost drops further. Add solar and part of the electricity is free.
| Heating system | Cost per useful kWh | Typical annual cost (12,000 kWh demand) |
|---|---|---|
| Gas boiler (90% eff.) | ~7.8p | ~£936 |
| Heat pump, standard tariff (SCOP 3.5) | ~6.9p | ~£828 |
| Heat pump, smart tariff (SCOP 3.5) | ~4.9p | ~£588 |
| Heat pump + 4kWp solar | ~3.5p effective | ~£450–£550 |
| Oil boiler | ~8–10p | ~£960–£1,200 |
| LPG boiler | ~10–12p | ~£1,200–£1,440 |
→ Heat pump vs gas boiler: full cost comparison → Air source heat pump running costs 2026 → Is gas cheaper than electricity? The real answer → Oil vs heat pump: 2026 cost comparison → LPG vs heat pump: off-grid cost comparison → The best heat pump tariffs in the UK
Sizing: What Size Heat Pump Do I Need?
Heat pumps are sized to your home's measured heat loss, not by bedroom count or your old boiler's kW rating. A proper room-by-room MCS heat-loss survey determines the exact kW figure — typically 5–8 kW for a well-insulated semi, 8–12 kW for a standard detached, 12–16 kW for larger or poorly insulated homes. Oversizing wastes money (short-cycling); undersizing disappoints in cold weather.
Do Heat Pumps Work in Cold Weather?
Yes. Modern R290 units operate down to -22°C. The coldest Leicester has ever recorded is -15.9°C (1981) — comfortably inside the range. SCOP dips slightly in deep cold but stays well above 2.5, and the seasonal average — which drives your bills — remains 3.5–4.0 across a full heating season.
→ Do heat pumps work in cold weather? The real data → Heat pump myths debunked
Radiators, Underfloor Heating and Hot Water
A heat pump runs at lower flow temperatures (35–45°C) than a boiler, so some radiators may need upsizing — typically 30–40% in our experience, not all. Underfloor heating is the ideal emitter. Hot water comes from a properly sized cylinder (we use the Heat Geek Super Cylinder for its fast recovery).
→ Do I need new radiators for a heat pump? → Best heat pump radiators → Heat pump hot water explained → Heat pump and underfloor heating
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Noise, Planning Permission and the Installation Process
Quality R290 units run at around 48 dB(A) at 3m — quieter than a fridge at arm's length. Most installations are permitted development (no planning needed), but there are siting rules to meet. A typical install takes 2–4 days with our ZeroDisrupt process.
→ How loud are heat pumps? Real noise levels → Planning permission for heat pumps → Our ZeroDisrupt installation process
Choosing the Right Heat Pump
The key factors: R290 refrigerant (future-proof, high-temperature capable), strong SCOP at realistic flow temperatures, low noise, wide modulation range, and the quality of the design and commissioning around it. The best heat pump is a good R290 unit correctly sized and expertly installed.
→ Best heat pump for a UK home in 2026 → R290 propane heat pumps explained → Ground source vs air source
Servicing, Lifespan and Warranties
A quality heat pump lasts 20–25 years with annual servicing (roughly £120–£200/year). The Vaillant aroTHERM Plus carries up to a 10-year warranty. Compare that to a gas boiler's 10–15 year life and you are likely to buy two boilers in the time one heat pump serves you.
→ Heat pump servicing and maintenance guide → How long do heat pumps last?
Is a Heat Pump Worth It?
For most UK homes in 2026, yes — especially when replacing oil, LPG or electric heating. On mains gas the case depends on the right tariff and good design, but with the grant, 0% VAT, lower running costs and a 20-year lifespan, the total cost of ownership typically beats a gas boiler over its life.
→ Are heat pumps worth it? An honest 2026 verdict → The honest pros and cons → Heat pumps in old houses
Smart Controls, Tariffs and Insulation
Weather compensation, smart scheduling and the right tariff can swing your running costs by hundreds of pounds a year. Insulation before (or alongside) a heat pump lowers heat loss and lets you fit a smaller, cheaper unit.
→ Smart heating controls and weather compensation → Insulation before a heat pump → How to reduce energy bills → What is an EPC rating? → Off-gas heating options compared
Why MCS Certification Matters
Only an MCS-certified installer can register your installation for the BUS grant. MCS also ensures a proper heat-loss survey, correct sizing and consumer-code protection. Without MCS you lose the grant entirely.
Get Your Free Estimate
Start with a free, no-obligation online estimate — it takes about a minute. When you are ready for an exact, designed price, we carry out a £250 home survey (fully refunded when you go ahead with your installation) covering full room-by-room heat-loss calculations and a bespoke system design.
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Frequently asked questions
A typical installation costs £11,000–£15,500 before grants. After the £7,500 BUS grant (or £9,000 off-gas) and 0% VAT, most households pay £4,000–£8,000 for a fully designed system including the cylinder, any radiator changes and commissioning.
Yes, when designed well. At a SCOP of 3.5 on a standard tariff, a heat pump delivers heat at roughly 6.9p per kWh versus about 7.8p for a 90%-efficient gas boiler. On a smart heat-pump tariff the gap widens further, and solar makes it wider still.
Yes. Modern R290 units like the Vaillant aroTHERM Plus operate down to -22°C. The coldest recorded temperature in Leicester was -15.9°C — well within the unit's range. Efficiency dips slightly in deep cold but the seasonal average stays high.
A quality air source heat pump lasts 20–25 years with annual servicing — roughly double a gas boiler. The Vaillant aroTHERM Plus carries up to a 10-year warranty when registered and serviced annually.
Usually some, not all. In our experience about 60–70% of existing radiators can stay; 30–40% benefit from upsizing to a double panel. Any changes needed are included in our fixed-price quote — there are no surprises.
The Boiler Upgrade Scheme gives £7,500 towards an air source heat pump. Off-gas-grid homes can claim an enhanced £9,000 (applications 21 July 2026 – 31 March 2027). Installations also attract 0% VAT until 31 March 2027.
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