Heat Pump vs Gas Boiler: Full Cost Comparison for UK Homeowners in 2026

For most UK homeowners, the boiler is the last thing they think about — until it breaks. But in 2026 a broken boiler creates a genuine decision point: replace like-for-like with a new gas combi, or take the leap to an air source heat pump with a £7,500 government grant attached. This guide cuts through the marketing noise and works through the numbers honestly, category by category, so you can see exactly which choice makes sense for your home.

Installation costs: what you actually pay upfront

New gas boiler

A replacement combi boiler costs £2,000–£3,500 fully installed in 2026, including the unit, labour, and building regulations compliance. Upgrading from a conventional system to a combi adds £500–£1,500 for extra pipework. Like-for-like swaps at the lower end of the range are the cheapest heating installation available in the UK today.

Air source heat pump (ASHP)

A fully installed ASHP with hot water cylinder costs £9,000–£14,000 before any grants. The spread is wide: the heat pump unit itself runs £3,000–£7,000 depending on output and brand; installation labour for a standard two-to-four day job adds £2,000–£4,000; a new unvented hot water cylinder (essential because most heat pumps cannot replace a combi's direct hot water function) costs £500–£1,500. Radiator upgrades, if your existing emitters are undersized, add a further £1,000–£3,000.

The Boiler Upgrade Scheme: £7,500 off a heat pump

The Boiler Upgrade Scheme (BUS), administered by Ofgem, provides a £7,500 upfront grant toward an air-to-water or ground source heat pump in England and Wales. Your MCS-certified installer applies on your behalf and deducts the grant from the invoice — you never handle the money. After the grant, most households pay £2,000–£7,000 for the full heat pump system, bringing it into genuine competition with a premium gas boiler installation. For a full guide to the application process, read our Warm Homes Plan guide which covers all four delivery routes including BUS.

Key BUS eligibility rules: you must own the property; it must be in England or Wales; you must be replacing a fossil fuel heating system; and the installation must be carried out by an MCS-certified installer. New builds are generally excluded (self-builds are an exception). The scheme runs until April 2028.

Side-by-side: upfront cost

Running costs: the electricity vs gas maths

Before diving into the cost comparison, if you want a step-by-step explanation of the technology itself, our guide on how a heat pump works covers the refrigerant cycle, COP, and SCOP in plain English. The single biggest running cost factor is the electricity-to-gas price ratio. Under the April–June 2026 Ofgem price cap, electricity costs an average of 24.67p/kWh and gas costs an average of 5.74p/kWh — a ratio of roughly 4.3:1. Under the July–September 2026 cap, electricity rises to 26.11p/kWh and gas to 7.33p/kWh (ratio 3.6:1).

A gas boiler with a seasonal efficiency of around 88–92% delivers useful heat at roughly 6.5–7.0p per kWh of heat output. A heat pump at SCOP 3.0 delivers heat at roughly 24.67 ÷ 3.0 = 8.2p per kWh of heat output at April 2026 electricity rates — more expensive than gas. But a heat pump at SCOP 3.5 delivers heat at 24.67 ÷ 3.5 = 7.0p per kWh, roughly matching gas. At SCOP 4.0, the cost drops to 24.67 ÷ 4.0 = 6.2p per kWh, cheaper than a gas boiler.

The real-world average SCOP across hundreds of monitored UK heat pump installations is approximately 3.87 (heatpumpmonitor.org, January 2026 data). A well-designed and correctly sized installation routinely achieves SCOP 3.5–4.5 in a reasonably insulated UK home. The key variables are: insulation quality, flow temperature (lower is better — aim for 45–55 °C or below), and whether you use a smart off-peak tariff.

Typical annual fuel bills

A 3-bedroom semi-detached home using around 12,000 kWh of useful heat per year would typically spend:

• Gas boiler: approximately £840–£960/year in fuel (at 5.74–6.5p/kWh effective heat cost)
• ASHP at SCOP 2.8–3.0: approximately £985–£1,055/year (worse than gas on standard tariff)
• ASHP at SCOP 3.5: approximately £840/year (comparable to gas)
• ASHP at SCOP 4.0: approximately £740/year (cheaper than gas)
• ASHP on a smart overnight tariff (e.g. 12p/kWh off-peak) at SCOP 3.5: approximately £410–£580/year

The verdict on running costs: if your heat pump achieves SCOP 3.5 or above and you are on a standard tariff, running costs are broadly similar to gas. On a smart off-peak tariff, a heat pump is significantly cheaper. If your heat pump is undersized, over-specified, or your home has poor insulation, SCOP may fall to 2.8–3.0 and bills will be higher. Insulation is the most important investment you can make before switching.

How SCOP determines whether a heat pump is cheaper or more expensive than gas

SCOP (Seasonal Coefficient of Performance) is the ratio of heat output to electricity input across a full heating season. Our dedicated guide to heat pump efficiency and SCOP explains the detail, but the headline rule for 2026 is: break-even SCOP = electricity tariff rate ÷ gas tariff rate.

At the April 2026 Ofgem cap (24.67p electricity, 5.74p gas), the break-even SCOP is approximately 4.3. That means you need a SCOP above 4.3 to be cheaper than gas on a standard tariff — achievable with a low flow temperature and good insulation, but not guaranteed. At the July 2026 cap (26.11p electricity, 7.33p gas), break-even SCOP falls to approximately 3.6, making heat pumps more competitive. As renewable energy generation continues to increase and electricity prices stabilise relative to gas over the long term, this ratio is expected to narrow.

The practical implication: homes that can run at a flow temperature of 45 °C or below (well-insulated properties, or those with upgraded radiators or underfloor heating) achieve the highest SCOP and the clearest running cost advantage. Victorian terraced homes with single-glazed windows, solid walls, and no loft insulation that must run at 70 °C flow temperature may see SCOP of only 2.5–3.0 — and bills higher than gas until the home is better insulated.

Maintenance costs

Annual service: boiler vs heat pump

Gas boilers should be serviced annually by a Gas Safe registered engineer. The average cost of a boiler service in the UK is £80–£120, with most homeowners paying around £100 for a standard check.

Air source heat pumps also require annual servicing, typically by an MCS-certified engineer or the manufacturer's service partner. Heat pump servicing costs £150–£200 per year on average in the UK, slightly higher than a boiler owing to the refrigerant circuit and additional checks required. Some manufacturers include service plans in their warranty terms.

Repair costs and reliability

Heat pumps have fewer combustion components than gas boilers and do not suffer flue corrosion or heat exchanger scaling from combustion gases. However, the refrigerant compressor — the most expensive component — can cost £1,000–£2,500 to replace if it fails outside warranty. Gas boilers are more prone to pump failures, diverter valve issues, and printed circuit board faults. Repair costs for both systems typically run £150–£600 per incident.

Lifespan: how long each system lasts

Gas boilers have a typical lifespan of 10–15 years. Manufacturers generally offer five-year warranties; with annual servicing, some units reach 15–20 years, but efficiency degrades over time and breakdowns become more frequent after 12 years.

Air source heat pumps typically last 15–25 years with regular servicing. The compressor is usually rated for 15–20 years; the rest of the system (circulation pump, controls, pipework) often outlasts this. Over a 20-year period, a UK household will typically replace approximately two gas boilers but only one heat pump — which affects the whole-life cost comparison significantly.

Whole-life cost comparison over 20 years

These figures are illustrative and depend heavily on energy prices over the period, actual SCOP achieved, and whether the heat pump requires a compressor replacement. On current tariff trajectories, the total cost of ownership is broadly similar over 20 years with a BUS grant — and swings in favour of the heat pump if electricity prices fall relative to gas, or if you pair it with solar panels.

Carbon footprint comparison

Natural gas combustion produces approximately 182g CO⊂2; per kWh of heat output (accounting for ~90% boiler efficiency from the 204g CO⊂2;/kWh of gas combustion).

The UK electricity grid carbon intensity has fallen sharply: the rolling 12-month average fell to approximately 122g CO⊂2;/kWh in early 2026, down from 131g/kWh the previous year, with April 2026 recording 93g/kWh as zero-carbon sources generated 78% of Britain's electricity. An ASHP at SCOP 3.0 has an effective carbon intensity of 122 ÷ 3.0 = 41g CO⊂2;/kWh of heat. At SCOP 3.5, this falls to 35g CO⊂2;/kWh. Compared with the 182g CO⊂2;/kWh of a gas boiler, this represents a carbon reduction of approximately 77–81%.

As the grid continues to decarbonise, the carbon advantage of heat pumps increases automatically without any change to the installed system. Carbon Brief analysis confirms that heat pumps already reduce carbon emissions associated with heating by approximately 85% relative to gas boilers on the current UK electricity mix.

The “boiler ban”: what is and is not confirmed policy

There is significant confusion about UK gas boiler policy. Here is what is actually confirmed as of June 2026:

• There is no confirmed ban on installing new gas boilers. The previously mooted 2035 deadline for phasing out new gas boiler installations in existing homes has not been legislated. The government has explicitly confirmed it will not force any homeowner to replace a working boiler.
• New build homes: regulations are moving to heat pump-ready specifications, with Future Homes Standard planned to require low-carbon heating in new builds from 2025 onwards — but implementation timelines have been revised multiple times.
• The Warm Homes Plan is the active policy vehicle: a £15bn programme targeting 5 million homes for energy efficiency and heat pump installations via grants and incentives, rather than mandates. The BUS is part of this strategy.
• The government's 450,000 heat pumps per year by 2030 target remains stated policy, supported by the BUS grant continuation until April 2028 and a £2.7bn funding commitment.

The practical implication: you will not be fined or forced to rip out a working gas boiler. However, gas boilers face a medium-term trajectory of rising carbon levies on gas, continued expansion of heat pump incentives, and gradual new-build restrictions. The question is not “must I switch now?” but “when switching makes financial and practical sense for my home.”

Verdict: when should you switch to a heat pump?

Switch now makes sense if:

• Your home is well insulated (EPC C or above, double glazing, loft and cavity wall insulation in place)
• You have or can install underfloor heating or larger radiators that allow a low flow temperature (45–55 °C)
• Your boiler is 10+ years old and approaching end of life
• You are planning to install solar panels and want to maximise self-consumption by heating with free electricity
• You qualify for the £7,500 BUS grant (England or Wales, replacing fossil fuel heating, owner-occupier)
• You can switch to a smart electricity tariff with cheap overnight rates

Wait or insulate first if:

• Your home is hard to insulate (solid brick Victorian terrace, no suitable roof or wall insulation)
• Your boiler is fewer than 5 years old and in good working order
• You cannot install a hot water cylinder (some flats, compact properties) — consider an hybrid heat pump as a stepping stone
• You are on a budget and cannot bridge the gap after the BUS grant
• Your home uses electric storage heaters — consider the £2,500 grant for an air-to-air heat pump instead (see our air-to-air heat pump grant guide)

The honest summary

A heat pump in a well-insulated UK home, installed with the BUS grant and paired with a smart tariff, is broadly cost-competitive with gas over its lifetime and delivers an 80%+ carbon saving today. In a poorly insulated Victorian terrace requiring high flow temperatures, it may cost more to run than gas until the home is better retrofitted. The path is almost always: insulate first, then heat pump. The BUS grant running until April 2028 means you have time to do this in the right order.

For a full breakdown of the best heat pump models available in the UK today, see our best air source heat pump buyer guide.

Homeowners with a large garden may also want to consider a ground source heat pump, which achieves a higher SCOP (3.5–4.5) than an air source system — see our ground source heat pump UK guide for a full cost and efficiency breakdown.