SCOP (Seasonal Coefficient of Performance) is a heat pump's average efficiency over an entire heating season, measured under EN 14825. Unlike COP, which describes one fixed condition, SCOP weights performance across mild and cold weather. A good SCOP for an air-to-water heat pump is 3.5 or higher; European subsidy schemes typically require at least 3.0.
How is SCOP measured?
EN 14825 defines a reference heating season — a set of outdoor temperatures and how many hours each occurs — for three European climate zones (average, warmer, colder). The heat pump is tested at several part-load points, and the results are weighted into a single seasonal figure. SCOP therefore captures things a single COP number hides: part-load behaviour, defrost losses, and backup heater use.
SCOP, ErP labels and ηs (seasonal space heating efficiency)
The EU energy label converts SCOP into ηs (eta-s), the seasonal space heating efficiency, using ηs ≈ SCOP / 2.5 (the EU primary energy factor for electricity). A SCOP of 3.5 corresponds to ηs of about 137–140% (the regulation deducts 3 percentage points for temperature control), which is class A+ for the 35 °C application — A++ starts at ηs 150%.
| SCOP (35 °C application) | ηs | ErP class |
|---|---|---|
| ≥ 4.45 | ≥ 175% | A+++ |
| 3.83 – 4.45 | 150 – 174% | A++ |
| 3.15 – 3.83 | 123 – 149% | A+ |
Why subsidy schemes use SCOP, not COP
Because SCOP reflects real seasonal behaviour, funding programs set their thresholds with it: Germany's BEG requires a JAZ (field equivalent of SCOP) of at least 3.0; the UK's MCS standard sets minimum seasonal performance for Boiler Upgrade Scheme eligibility. A machine with an impressive A7/W35 COP but poor cold-weather modulation can still fail a SCOP threshold.
How to improve the SCOP of an installed system
- Design for the lowest possible flow temperature — underfloor heating or oversized radiators.
- Use weather-compensated control rather than a fixed flow setpoint.
- Size the heat pump to the building's heat load; oversizing causes cycling losses.
- Add a correctly sized buffer tank to prevent short-cycling.
- Keep the outdoor unit free of airflow obstructions and recirculation.
Frequently asked questions
Is SCOP the same as JAZ (Jahresarbeitszahl)?
They are close relatives. SCOP is a laboratory seasonal value under EN 14825; JAZ is the measured seasonal performance of a real installation in the field. German BAFA/BEG funding rules are written in terms of JAZ, calculated for the specific building.
Which climate zone applies to the SCOP on a datasheet?
Unless stated otherwise, the 'average' European climate profile (reference city Strasbourg). Manufacturers may additionally publish colder-climate (Helsinki) and warmer-climate (Athens) values — relevant when comparing units for Scandinavia or the Mediterranean.