What is SCOP?
Summary
SCOP (Seasonal Coefficient of Performance) measures how many units of heat a heat pump delivers for each unit of electricity it consumes, averaged across a full UK heating season. A SCOP of 3.0 means the pump delivers 3kWh of heat for every 1kWh of electricity.
Why SCOP matters
Higher SCOP means lower running costs. A pump with SCOP 4.0 costs 25% less to run than one rated 3.0 for the same heat output. The UK government's Boiler Upgrade Scheme requires heat pumps to meet minimum efficiency standards, reported as SCOP.
SCOP vs COP
COP (Coefficient of Performance) measures efficiency at a single outdoor temperature (typically 7°C). SCOP is more realistic because it averages performance across the full range of UK winter temperatures (from -10°C to +15°C). Always use SCOP when comparing UK heat pumps.
Typical SCOP ratings in the UK
| SCOP | Rating | Notes |
|---|---|---|
| 2.5 | Poor | Poorly sized or older system |
| 3.0 | Typical | Most UK installations achieve this |
| 3.5 | Good | Well-designed, properly sized |
| 4.0+ | Excellent | Optimal system with low flow temperatures |
What affects SCOP?
- Flow temperature: Lower flow temp (35-45°C) = higher SCOP. Requires larger radiators or underfloor heating.
- Sizing: An oversized pump cycles on/off frequently, reducing efficiency.
- Insulation: Better insulation allows lower flow temps.
- Climate: Milder UK winters help. Scotland averages slightly lower SCOP than southern England.
Sources
- UK Department for Energy Security & Net Zero, Boiler Upgrade Scheme: eligibility criteria, 2024
- Energy Saving Trust, Air source heat pumps, accessed May 2026
- MCS (Microgeneration Certification Scheme), Heat Pump Calculator methodology, v2.1
Try the calculator: Estimate your heat pump running costs using your home size and SCOP rating.