Your Home Climate
Running-cost comparison

Heat pump vs gas boiler; the honest running-cost comparison

What an air-source heat pump actually costs to run compared with a modern gas boiler in a typical UK home, why the tariff matters more than the unit, and the conditions under which the heat pump genuinely wins.

Editorial confidence
High confidence. Multiple regulator, government or academic sources agree.
Last reviewed
1 June 2026 · next review 1 September 2026

Who this advice is for

Applies to

  • Owner-occupied UK homes weighing a like-for-like replacement of an existing gas boiler
  • Homes with reasonable insulation; loft topped up, cavities filled where present
  • Households willing to look at heat-pump-specific tariffs as part of the decision

Not intended for

  • Homes still on a poorly insulated solid-wall fabric; the fabric work has to be modelled alongside the heating change
  • Off-grid properties; the comparable here is oil or LPG, not mains gas
  • Homes that cannot or will not switch electricity tariff

You may not need to read the rest of this page

You probably already have enough to act if:

  • You wanted a defensible answer to 'will the bill go up or down' before you committed to a heat-pump quote
  • You wanted to know whether tariff choice is part of the heat-pump decision (it is)
Estimate your sizing and likely running cost

This is probably the wrong page for you if:

  • You wanted a model of your specific home; only a heat-loss survey can do that
  • You are off the gas grid; the relevant comparison is oil or LPG and the maths flips in the heat pump's favour earlier

Well-designed UK heat pump SCOP range

3.2 to 4.8

Source: Microgeneration Certification Scheme · Seasonal Coefficient of Performance for an MCS-installed air-source heat pump with appropriate emitter sizing and flow temperature; the lower end represents a typical retrofit, the upper end a well-designed system in a low-temperature emitter circuit.

Ofgem default tariff cap, electricity unit rate

27 p/kWh

Source: Office of Gas and Electricity Markets · Used as the reference unit rate for the comparison; heat-pump-specific tariffs typically discount this by a third or more during off-peak windows.

Indicative annual heating cost on a heat-pump tariff, three-bed semi

£900 to £1,300

Source: Energy Saving Trust · Energy Saving Trust scenarios for a well-insulated three-bedroom semi with a SCOP at the lower end of the well-designed range, on a representative heat-pump-specific tariff.

What to do, and why first

01

Decide the tariff before you sign the install quote

Why this comes first

On a flat domestic electricity tariff, a heat pump comes out roughly level with a modern condensing gas boiler in most UK homes; sometimes a little better, sometimes a little worse. On a heat-pump-specific tariff with discounted off-peak windows, the same heat pump in the same home runs roughly twenty to thirty per cent cheaper than gas. The tariff is the lever; choose it before the install rather than after.

Evidence

Ofgem publishes the default tariff cap quarterly; suppliers such as Octopus and British Gas publish their heat-pump tariffs as named products with documented unit rates; Energy Saving Trust scenarios show the running cost difference is dominated by tariff choice.

Ofgem · Octopus · EST

Confidence

High confidence. Multiple independent sources agree on the direction and the order.

Exceptions
  • Households who cannot switch supplier (some park-home and shared-meter arrangements)
  • Properties without a smart meter; most heat-pump tariffs require one
Next step
Open the running-cost estimate
02

Compare SCOP, not the lab-quoted COP

Why this comes first

Heat pump marketing leans on the laboratory Coefficient of Performance at 7 °C outside and 35 °C flow. The number that actually drives your bill is the Seasonal Coefficient of Performance across a real British winter, which sits roughly half to one whole point below the COP. A SCOP of 3.5 in your home means one unit of electricity buys three and a half units of heat across the year; the COP on the box might say four or higher.

Evidence

MCS MIS 3005 requires installers to design to a stated SCOP at typical flow temperature for the system; Energy Saving Trust field-trial guidance treats SCOP as the meaningful running-cost input.

MCS · MIS 3005 · EST

Confidence

High confidence.

Exceptions
  • Newer underfloor-heating-only systems where the design flow temperature is close to the COP test condition
Next step
See sizing and SCOP guidance
§01

The headline answer

On a standard flat electricity tariff with an MCS-installed heat pump achieving a SCOP of about 3.5, the annual heating bill in a well-insulated three-bedroom UK semi sits very close to the cost of running a modern condensing gas boiler in the same house. The difference either way is typically smaller than the noise in any single household's annual usage.

On a heat-pump-specific tariff such as Cosy Octopus, British Gas Heat Pump or EDF Heat Pump Tracker, the same heat pump in the same house runs roughly twenty to thirty per cent cheaper than gas over the year. The mechanism is simple: those tariffs price off-peak electricity below the unit cost of gas, and the heat pump shifts most of its work into those windows.

§02

Why SCOP is the number that matters

A heat pump's lab Coefficient of Performance is measured at conditions favourable to it; mild outside, low flow temperature, steady-state operation. A real British winter is colder, and most retrofit systems run a higher flow temperature than the lab test. The Seasonal Coefficient of Performance is the same machine averaged across a full UK heating season, and it is the figure that determines how many units of electricity the home actually consumes.

A well-designed retrofit will land at SCOP 3.2 to 3.8 in real use. A new build with underfloor heating and weather compensation can reach 4.5 or above. Anything quoted below 2.8 in an installer's design document should be treated as a warning sign about emitter sizing or flow temperature; it is not a comfortable place from which to compare against a 90 per cent efficient gas boiler.

§03

Where the heat pump wins outright

Off-grid homes currently heated by oil or LPG are the clearest win. The comparable fuel cost there is well above mains gas, and a heat pump on a standard tariff already beats them comfortably; on a heat-pump tariff the gap widens.

Well-insulated newer homes with reasonable emitter sizing also win on most tariffs because the SCOP sits at the upper end of the band.

The boundary case is the older, harder-to-insulate house on a flat tariff; there the heat pump can land slightly worse than the gas boiler it replaced if the system is run inefficiently. A heat-pump-specific tariff usually rescues that case.

§04

The carbon picture, separately

Running cost and carbon are two different conversations on the same bill. Electricity has been decarbonising faster than gas for over a decade, so even at parity on running cost a heat pump emits less carbon per unit of heat delivered, and that gap widens every year as more renewables join the grid. The carbon comparison is the more durable one; the running-cost comparison moves with tariffs.

Evidence behind this page

Every recommendation on this page is traceable to its source. Click a publication to read the original.

Real homes, public sources

The honesty layer
What we know
  • The Ofgem default cap and the published unit rates of the main UK heat-pump tariffs
  • The SCOP range a well-designed MCS install should achieve in normal UK conditions
What varies
  • Individual household behaviour, hot-water usage and target temperatures
  • How quickly each supplier's heat-pump tariff repositions as cap rates change
What we don't know
  • Whether the heat pump in your specific house will land at SCOP 3.2, 3.5 or 4.5; only commissioning data tells you that

The knowledge graph

Technologies
  • Air-source heat pump
  • Insulation
  • Smart controls
Problems it answers
  • Energy bills feel too high
Property types
  • Victorian terrace

Sourced from the Your Home Climate knowledge engine; every connection updates centrally.

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