Choosing between a heat pump and a gas boiler is not only a heating decision. It is a decision about upfront cost, grant support, and how well each system suits the building you already have. This guide sets out what is confirmed by government sources today, so you can put the right questions to an assessor before you commit.
The basic difference
A gas boiler burns gas to heat water directly. A heat pump extracts heat from the outside air, or from the ground in a ground source system, and concentrates it to heat your home and hot water, using electricity to run the process rather than to generate the heat itself.
Both can heat a home to a comfortable standard. Which one suits yours depends on your current system, your insulation, the size and layout of the building, your emitters and your budget. None of those is something a general article can assess for you, and any page that tells you the answer without seeing the property is guessing.
Where the grant sits
There is a government grant towards a heat pump and there is no equivalent for a new gas boiler. That asymmetry is real and it is the single largest financial difference between the two options at the point of purchase.
The current amounts, the eligibility rules and the 120 day condition are set out in full in the Boiler Upgrade Scheme guide. The short version is that it is claimed by your MCS certified installer rather than by you, and it comes off the invoice.
The running cost question, answered honestly
You will find confident claims that a heat pump is cheaper to run than a gas boiler, and equally confident claims that it is more expensive, usually with a specific annual figure attached.
We checked GOV.UK, Ofgem and MCS directly. None of them publishes a comparative running cost figure for heat pumps against gas boilers. Every pound figure in circulation comes from a comparison site, a calculator or a lead generation business, and they contradict each other in both directions.
We are not adding to them, and we are not constructing our own estimate either. Combining a live unit rate with an assumed boiler efficiency and an assumed seasonal performance factor produces a number that looks authoritative and is an assumption stack. The honest answer is that running cost depends on your electricity and gas tariffs, how well the building holds heat, how the system is sized and designed, and how it is then operated. Those are properties of your house, not of the technology.
If running cost is central to your decision, the reliable way to answer it is a heat loss assessment and system design from an MCS certified installer, priced against your own tariffs. We would rather say that than give you a number we cannot stand behind.
If the comparison is not hypothetical because the boiler has already failed, the timescales change the answer. Your boiler has failed, what are your realistic options deals with that situation directly.
What actually decides it for most properties
Before the comparison is even meaningful, three things about the building shape the answer.
How much heat does it lose? A heat pump delivers heat at a lower temperature than a boiler. In a building that loses heat quickly, that is a harder job.
Will the existing radiators and pipework carry it? A lower flow temperature usually means larger emitters. This is a common and often unbudgeted line in a heat pump quotation.
Is there room, and is there power? There is an outdoor unit, usually a hot water cylinder, and an electrical supply that has to be adequate. GOV.UK’s position is that most heat pumps can be installed without changes to the electricity supply, and “most” is not “yours”.
If those three are unresolved, comparing the two systems on price is premature. Whether your property is ready works through each of them.
If the comparison you are actually making is against oil or LPG rather than mains gas, note that a higher grant rate is currently available for off-gas-grid properties, with an end date. See the £9,000 off-gas-grid grant.
Where Eco Connect fits
We give independent advice on renewable and low carbon options for homes, farms and businesses. We do not install heat pumps or gas boilers, and we are not MCS certified. Where a heat pump looks like the right direction, the installation work goes to a vetted delivery partner who carries out the assessment and the work to MCS standards.
Sometimes the advice is that nothing should be bought yet. That is a less appealing sentence than a grant figure, which is why it tends not to get said.
This article is general information, not financial, legal or technical advice, and it is not a substitute for a property-specific assessment. Grant rules, amounts and eligibility change. Information correct as of 26 August 2026.
