BrightGridEvery gas boiler eventually needs replacing, and increasingly the honest choice is between a new gas boiler and a heat pump. This isn't a simple 'heat pumps are always better' or 'boilers are always cheaper' answer — it genuinely depends on your home. Here's the comparison without the sales pitch either way.
How the two technologies actually differ
A gas boiler burns fuel to heat water directly, reaching high flow temperatures (typically 60–80°C) very quickly. A heat pump extracts latent heat from outside air and concentrates it using a compressor, most efficiently at lower flow temperatures (typically 35–45°C) delivered over a longer, steadier heating cycle.
That difference in flow temperature is the single biggest factor in whether a heat pump suits your home as-is, or needs some preparation first.
Installation cost comparison
| Gas boiler (like-for-like) | Air-to-water heat pump | |
|---|---|---|
| Typical installed cost | £2,500 – £4,000 | £9,000 – £14,000 |
| Government grant available | None | Boiler Upgrade Scheme, currently up to £7,500 |
| Radiator/pipework upgrades often needed | Rarely | Often, especially in older or poorly insulated homes |
| Typical net cost after grant | £2,500 – £4,000 | £4,000 – £8,500 |
Running cost comparison
Running costs depend heavily on the relative price of gas versus electricity, and on the heat pump's efficiency (its Coefficient of Performance, or CoP — a CoP of 3 means it delivers 3kWh of heat for every 1kWh of electricity used).
- A well-installed heat pump with a CoP of 3+ typically runs at broadly similar cost to a gas boiler at current UK electricity and gas prices — sometimes slightly cheaper, sometimes slightly more, home by home
- Pairing a heat pump with solar and a battery changes this significantly, since a meaningful share of the electricity it uses can come from your own generation rather than the grid
- A poorly sized or badly installed heat pump running at a low CoP can end up more expensive to run than a gas boiler — correct sizing and installation quality matter more here than with boilers
The honest summary
On running costs alone, a well-installed heat pump is usually roughly cost-neutral against gas, not dramatically cheaper. The stronger financial case comes from combining it with solar and battery, and from the £7,500 Boiler Upgrade Scheme grant reducing the installation cost gap.
Is your home actually suitable?
Insulation
Heat pumps run most efficiently delivering steady, lower-temperature heat over longer periods. A well-insulated home holds that heat well; a poorly insulated one loses it quickly, forcing the heat pump to run harder and less efficiently. Loft and cavity wall insulation are worth addressing first if they're currently poor.
Radiators and pipework
Because heat pumps deliver heat at a lower flow temperature than a boiler, existing radiators are often undersized for the new system and need upgrading to larger radiators or, ideally, underfloor heating, to heat the room properly at the lower temperature.
Hot water
Air-to-water heat pumps heat a hot water cylinder rather than providing water on demand like a combi boiler, so homes without cylinder space (common in flats with combi boilers) may need to find room for one, or may be better suited to an air-to-air system that handles space heating and cooling only.
So which should you choose?
If your gas boiler still has years of life left, there's rarely urgency to switch early on cost grounds alone. If it's failing or near end of life, and your home has (or can reasonably get) decent insulation and cylinder space, a heat pump paired with the Boiler Upgrade Scheme grant is genuinely competitive on both running cost and long-term value — particularly alongside solar.
Find out if your home is heat-pump ready
We'll assess your insulation, radiators and hot water setup properly, and confirm current grant eligibility.
Explore heat pumpsFrequently asked questions
Will a heat pump keep my house as warm as a gas boiler?
Yes, provided it's correctly sized and your radiators (or underfloor heating) are appropriately sized for the lower flow temperature. An undersized heat pump or under-sized radiators are the most common causes of homes feeling colder after switching.
Do I need to replace all my radiators?
Not always — it depends on how oversized your current radiators already are relative to each room's heat loss. A proper heat loss survey (not a guess) will confirm exactly which radiators, if any, need upgrading.
How noisy is an air source heat pump?
Modern units typically run at around 40–60 decibels at one metre, similar to a quiet dishwasher, and are usually sited away from bedroom windows during installation planning.
Can I keep my gas boiler as a backup?
Technically possible with a hybrid system, though most homes claiming the Boiler Upgrade Scheme grant fully replace the gas boiler, since the grant is specifically for heat pumps as the primary heat source.
Marcus Webb
Head of Engineering at BrightGrid Energy
