SnapEnergyLab
Heating

What a heat pump actually costs to run

Running cost is heat demand divided by seasonal efficiency, multiplied by your electricity price. Every disagreement is about one of those three numbers.

Published 23 August 2026 · Published by SnapEnergyLab. Methodology and default assumptions are documented separately.

An air-source heat pump beside a house on a frosty evening, with warm light and a person visible in the windows

Quick answer

Running cost is three numbers: how much heat your home needs, how efficiently the heat pump delivers it, and what you pay for electricity. Divide the first by the second, multiply by the third.

Every disagreement about heat pump economics — and there are many — is a disagreement about one of those three inputs, not about the arithmetic.

How to read the numbersYour inputSite defaultCalculated result
Annual heat demand
15,000 kWh
Your input
SCOP
3.2
Your input
Annual running cost
≈ 1,406
Calculated result

The calculation

  1. electricity used (kWh) = annual heat demand (kWh) ÷ SCOP
  2. annual running cost = electricity used (kWh) × price per kWh
  4. example: 15,000 ÷ 3.2 = 4,688 kWh
  5. 4,688 × 0.30 = 1,406

SCOP is the seasonal coefficient of performance — heat delivered divided by electricity consumed across a whole heating season. A single-point COP is not a substitute.

Getting the heat demand right

Heat demand is the quantity you are replacing, not the fuel you were buying. If you currently heat with gas, multiply your annual gas consumption by the boiler’s seasonal efficiency — typically 0.85 for a non-condensing boiler, 0.90 for a condensing boiler running at appropriate flow temperatures.

If you heat with electric resistance heaters, the arithmetic is easier: every kWh of electricity became a kWh of heat, so your heating electricity is your heat demand.

Both routes are far better than a room-by-room estimate, because they are grounded in metered consumption for your actual building and your actual comfort preferences.

Annual heating cost against seasonal performance, for a 15,000 kWh heat demand0200040001234SCOP (seasonal coefficient of performance)Annual electricity cost
15,000 kWh of delivered heat at an illustrative price of 0.30 per kWh (not a SnapEnergyLab site default — the site default electricity rate is 0.18/kWh; see Assumptions). The curve is steep at the left: the difference between SCOP 2.0 and 2.5 costs more than the difference between 3.5 and 4.5, which is why poorly commissioned systems are disproportionately expensive.
Show the plotted values
SCOPAnnual cost at 0.30 per kWh
14500
1.53000
22250
2.51800
31500
3.51286
41125
4.51000

Worked example: replacing a gas boiler

  1. Annual gas consumption17,600 kWhYour input
  2. Boiler seasonal efficiency85%Site default
  3. Delivered heat demand17,600 × 0.85 = 14,960 kWhCalculated result
  4. Heat pump SCOP3.2Your input
  5. Electricity required14,960 ÷ 3.2 = 4,675 kWhCalculated result
  6. Electricity cost at 0.304,675 × 0.30 = 1,403Calculated result
  7. Gas cost at 0.0917,600 × 0.09 = 1,584Calculated result
Difference in annual running cost≈ 181 saved

Laboratory SCOP versus what you will get

Published SCOP is measured under EN 14825 at a defined flow temperature and climate. Field trials consistently find installed systems performing below their laboratory figure, and the gap is almost always explained by the same handful of causes.

Flow temperature. The single biggest lever. A system designed around 35 °C flow into underfloor heating performs far better than the same unit pushed to 55 °C to feed undersized radiators. Each degree of flow temperature reduction is worth roughly 2–2.5% in efficiency.

Cycling. An oversized unit short-cycles at mild temperatures, which wastes energy on repeated start-up and degrades measured performance.

Hot water. Domestic hot water requires 50 °C or more, so it runs at a much lower COP than space heating. A system doing both has a blended performance below its space-heating figure.

Auxiliary heat. Immersion elements used for defrost, legionella cycles or cold-snap backup run at COP 1 and are frequently excluded from headline figures.

Compare running costs with your own numbers

Enter your heat demand, the SCOP you expect and your own electricity price to compare against resistance heating, with every intermediate value shown rather than hidden behind a single saving figure.

Open the heat pump savings calculator

Assumptions and limitations

  • This is a running-cost calculation only. It excludes installation cost, grants, maintenance, and any radiator or insulation work a heat pump installation may require.
  • Prices used in this article (0.30/kWh electricity, 0.09/kWh gas) are illustrative round numbers chosen to show the method, not SnapEnergyLab's site default electricity rate (0.18/kWh, see Assumptions) or any market rate. Fixed standing charges are excluded and affect the comparison when switching away from gas entirely.
  • A single annual SCOP hides the fact that efficiency and heat demand vary together across the season, with the worst efficiency occurring on the coldest days.
  • Field-measured seasonal performance is commonly below the laboratory SCOP on a datasheet. Treat the datasheet figure as an upper bound.

Sources

  1. EN 14825 — Testing and rating at part load conditions, seasonal performance — European Committee for Standardization

    Supports: Definition of SCOP and the part-load test conditions from which it is derived.

  2. Heat pump performance field trials — Energy Systems Catapult / BEIS Electrification of Heat project

    Supports: Measured in-situ seasonal performance factors for domestic heat pumps, typically below laboratory SCOP.

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