Heat Pump COP and SCOP: Why Efficiency Figures Matter

Heat pumps advertise efficiencies of 300%, 400%, even 500%. But what do these numbers actually mean, and how do they translate into your electricity bills? COP and SCOP are the two figures that matter most when comparing models or assessing whether your existing system is performing well. Understanding the difference could save you hundreds of pounds a year.

What is COP?

COP stands for Coefficient of Performance. It is a snapshot measurement: at a specific set of conditions — a defined outside air temperature and a defined flow temperature to the heating system — how many units of heat does the pump deliver per unit of electricity consumed? A COP of 3.0 means 3 kWh of heat for every 1 kWh of electricity. A COP of 4.0 means 4 kWh — the "400% efficiency" figure you see in marketing materials.

The catch is that COP is measured at a single test point, defined by European standard EN 14825. Common test points use outside temperatures of -7°C, +2°C, and +7°C. A unit rated COP 4.2 at +7°C may drop to COP 2.5 at -7°C. Neither figure tells you what the pump will average across a UK heating season — that is what SCOP is for.

What is SCOP?

SCOP — Seasonal Coefficient of Performance — is calculated across an entire heating season using a weighted average of different operating conditions. The weighting reflects the typical distribution of outside temperatures in your climate zone. The EU uses three standard reference cities: Strasbourg (average climate), Helsinki (cold), and Athens (warm). UK homes are closest to Strasbourg, so a manufacturer's stated SCOP figure is directly applicable.

SCOP is what determines your annual heating electricity consumption. If your home needs 12,000 kWh of heat per year and your heat pump achieves SCOP 3.8, you will consume approximately 3,158 kWh of electricity for heating (12,000 divided by 3.8). At 24.5p/kWh, that is around £774 per year in heating electricity — a figure that varies dramatically depending on the SCOP your installation achieves.

Typical SCOP values by system type

What affects your real-world SCOP?

Flow temperature

The single biggest factor. Heat pumps become significantly less efficient as the temperature gap between the outside air and the flow temperature to your heating system increases. Running at 35°C flow (suitable for underfloor heating or well-sized radiators) might give SCOP 4.0. The same unit running at 55°C (for undersized radiators) might achieve only SCOP 2.5. This is why correctly sized radiators are not a luxury — they are central to the economics of switching.

Outside air temperature distribution

The UK's mild maritime climate is well-suited to air source heat pumps. Most heating hours occur at outside temperatures between 0°C and 10°C — not at -10°C as many homeowners assume. Very cold snaps do reduce efficiency and may trigger backup electric heater elements, but they represent a small proportion of total annual heating hours in most UK locations, particularly in England and Wales.

Installation quality and controls

A heat pump installed without weather compensation — a control that automatically adjusts flow temperature based on outside air conditions — will typically run less efficiently than one correctly set up. Weather compensation allows the pump to lower flow temperature during mild weather, boosting SCOP across the season. An experienced installer commissions this at handover; a rushed one may leave it at a fixed setpoint that wastes energy throughout winter.

What SCOP do you need to beat gas costs?

At Q1 2026 Ofgem tariffs (electricity 24.5p/kWh, gas 6.4p/kWh), the electricity-to-gas price ratio is 3.83. A heat pump needs a SCOP of at least 3.83 to produce heat at the same cost per kWh as a gas boiler. At SCOP 4.0 it is cheaper than gas; at SCOP 3.5 it costs slightly more. For oil heating (approximately 6.9p/kWh effective at current prices), the break-even SCOP is around 3.55 — comfortably within reach for a modern, well-installed air source unit.

For LPG users, the comparison is even more compelling: LPG at around 7.2p/kWh effective means almost any functioning heat pump saves money on fuel costs alone, before the £7,500 BUS grant is factored in.

How to check your heat pump's actual efficiency

Most modern heat pumps report efficiency data through manufacturer apps: Mitsubishi Ecodan via MELCloud, Vaillant via myVAILLANT, Daikin via Daikin Online Controller, Samsung via SmartThings. If your installer configured remote monitoring at commissioning, you can view real seasonal COP data directly in the app.

Third-party monitoring or a heat meter combined with a smart electricity meter can calculate real SCOP if manufacturer monitoring was not set up. The Energy Saving Trust's Heat Pump Field Trials found well-installed UK heat pumps averaging SCOP 2.5–3.5 across all installation types, with better-specified systems reaching 3.8–4.5. If your system falls below 2.5, ask your installer to review flow temperature settings, weather compensation calibration, and whether backup heater elements are running unnecessarily.