SEER (Seasonal Energy Efficiency Ratio) and SCOP (Seasonal Coefficient of Performance) are the indexes that measure an air conditioner’s seasonal energy efficiency: the first applies to cooling operation, the second to heat-pump heating.
How they work
Unlike a lab measurement under fixed conditions, SEER and SCOP simulate an entire season of use, with outdoor temperatures that vary throughout the days and workloads ranging from full capacity to partial-load operation — the most common condition in real use, since an air conditioner rarely runs flat out all the time. The calculation weighs these scenarios according to standardized European climate data, producing a number that better represents a full season’s consumption than a single instantaneous measurement.
Why they replaced EER
The old EER (Energy Efficiency Ratio) measured efficiency under a single fixed lab condition, typically at full load and 35°C outdoors. It was a useful figure for comparing models in a lab, but not very representative of real consumption, where climate varies day by day and the unit almost always runs at partial load. For several years now, European energy labels have relied solely on SEER and SCOP.
How to read the value
The higher the number, the less energy the unit needs to remove (or produce) the same amount of heat: a model with a SEER of 8.5 consumes noticeably less than one with a SEER of 6.1 for the same cooling effect. Higher values are typically found on high-end Inverter units, while cheaper or non-Inverter models generally stay at more modest values.
The link to energy class
SEER and SCOP are the two figures behind the calculation of the energy class (A+++, A++, A+…) shown on the European label: they’re not just useful to those reading spec sheets in detail, they’re already summarized into a single letter meant for quick comparison. We cover this in detail in the entry dedicated to air conditioner energy classes, and more generally in our complete guide on how to choose an air conditioner.