Heat pumps · 6 min read
Heat pump vs gas boiler: how the running costs actually compare
A straightforward way to compare the two without spreadsheets — and the three variables that decide the answer for your house.
The only comparison that means anything
Compare cost per unit of heat delivered, not cost per unit of fuel bought. A gas boiler at 90% efficiency turns 1 kWh of gas into 0.9 kWh of heat. A heat pump with a seasonal performance factor of 3.2 turns 1 kWh of electricity into 3.2 kWh of heat.
So the comparison is: (gas price ÷ 0.9) against (electricity price ÷ SPF). Whether the heat pump wins depends almost entirely on the ratio between the two tariffs and on the SPF your system actually achieves.
Three variables that decide it
Everything else is noise.
- The electricity-to-gas price ratio, including whether you are on a heat pump tariff.
- Your system's real seasonal performance factor, which is set by flow temperature — which is set by emitter sizing.
- What you are replacing. Coming off oil, LPG or old electric heating, the saving is large and obvious. Coming off a modern condensing gas boiler on a standard tariff, it is much closer.
Where oil and LPG homes sit
This is the clearest case. Off-grid Hampshire property currently burning oil generally sees a substantial reduction, and it is also where the grant makes the largest dent in the capital cost. A large part of our patch — West Wellow, Stockbridge, the villages around Romsey and out towards Kings Worthy — is off the gas grid.
The middle path: hybrid
A hybrid runs an air source heat pump alongside your existing gas or oil boiler. The heat pump covers most of the year; the boiler handles the coldest days and peak hot water. It is not the cheapest to run of the three options, but it de-risks the change for properties that are not yet ready for a full conversion. We install and maintain both halves.
Questions we get asked
Will my bills definitely go down?
Not automatically. A poorly designed heat pump running at a high flow temperature can cost more than a good gas boiler. Design quality is the deciding factor, which is why we survey before quoting.
What SPF should I expect?
It depends on the design flow temperature and the property. We state the design assumptions in the quotation so you can see what the estimate is based on.
Want this checked against your own property?
A survey costs nothing and turns general advice into specific numbers. We are Gas Safe, NICEIC and MCS accredited (NIC601962), so whichever direction the answer points, the same team can do the work.
More guides
Keep reading
Is a heat pump right for my Hampshire home?
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Read guideReady to get started?
Tell us about your property and we will come back with a written, itemised quotation — not a phone estimate.