The debate about whether to replace a gas boiler with an air source heat pump has intensified as the UK approaches its 2035 new gas boiler ban and as heat pump prices have fallen significantly. But for most homeowners, the question is simpler: which option makes the most financial sense right now, in 2026? This guide provides an honest, detailed comparison.
Installation Costs
Gas boiler replacement: A new A-rated combi gas boiler, installed like-for-like in most properties, costs approximately £2,000–£4,000 including installation. The lower cost makes it an attractive short-term option, particularly for landlords with properties that don't yet need full heating upgrades.
Air source heat pump: An ASHP system costs approximately £8,000–£15,000 installed. However, the Boiler Upgrade Scheme (BUS) grant of £7,500 reduces this to an effective net cost of £500–£7,500 for eligible properties. When combined with solar panels (which power the heat pump), the total package represents a complete transition away from fossil fuel heating.
Running Costs: The Critical Comparison
This is where the comparison becomes more complex and where the combination of a heat pump with solar panels changes everything.
Gas boiler running costs: A typical 3–4 bed home using a gas boiler for central heating and hot water uses approximately 12,000–15,000 kWh of gas per year. At the current gas unit rate of approximately 6.5–7.5p per kWh, this costs approximately £780–£1,125 per year in gas alone (plus the standing charge of approximately £110/year).
Heat pump running costs (grid electricity): An ASHP with a COP of 3.5 would use approximately 3,430–4,285 kWh of electricity to deliver the same heat output. At 24–28p per kWh, this costs approximately £823–£1,200 per year. Without solar panels, a heat pump powered entirely by grid electricity offers limited cost savings over gas in 2026, particularly at higher electricity prices.
Heat pump running costs (with solar panels): This is where the economics become compelling. A 4.5kWp solar system generates approximately 4,500 kWh per year. If a significant portion of heat pump operation is scheduled during daylight hours (particularly for hot water heating, which can be done via a cylinder during the middle of the day), a well-designed solar + ASHP system can provide approximately 40–60% of the heat pump's electricity from free solar generation. This reduces annual running costs to approximately £330–£500 per year — significantly less than a gas boiler.
10-Year Cost Comparison
Assuming a property installs a gas boiler today at £3,000 versus a heat pump + solar system at a net cost of £12,000 after the BUS grant and 0% VAT, and assuming gas prices remain constant:
- Gas boiler (10 years): £3,000 install + (£950 avg annual gas cost × 10) = £12,500 total
- Heat pump + solar (10 years): £12,000 net install + (£400 avg annual running cost × 10) = £16,000 total
On these figures, a heat pump + solar system breaks even with a gas boiler at approximately year 14–16 — primarily because the high upfront cost difference takes time to recover through lower running costs. However, this comparison does not include the Smart Export Guarantee income from surplus solar generation (approximately £1,500 over 10 years), potential future increases in carbon taxes on gas, or the capital value of having solar panels on your property.
The 2035 Gas Boiler Ban Factor
From 2035, new gas boiler installations will be banned in the UK. Homeowners who install a gas boiler today are making a 10–15 year investment in a technology with a fixed end date. A heat pump installed today, by contrast, is a 25-year investment in the technology that will be standard in UK homes for the foreseeable future. Learn more about heat pump installation from D&R Energy.
