SEER, SCOP and the energy label for air conditioners

Air conditioners up to 12 kW carry an energy label under Regulation (EU) No 626/2011, the text of which is also published on legislation.gov.uk ^1,2. For split systems, two numbers matter most: SEER for cooling and SCOP for heating. Understanding them lets you compare models far better than the letter alone.

What do SEER and SCOP measure?

• SEER (Seasonal Energy Efficiency Ratio): how much heat the unit removes over a whole cooling season per unit of electricity. A SEER of 7 means 7 kWh of cooling for 1 kWh of electricity.
• SCOP (Seasonal Coefficient of Performance): the same idea for heating over a heating season. A SCOP of 4 delivers 4 kWh of heat per kWh of electricity.

“Seasonal” is the key word. Air conditioners spend most of their time at part load and at changing outdoor temperatures. SEER and SCOP weight those conditions, unlike the older EER and COP figures, which describe a single full-load test point ¹.

The label classes

Since 1 January 2019 the scale for split systems has run from A+++ to D ¹:

Source: Annex II of Regulation 626/2011 ¹.

Note how wide the A++ cooling band is: SEER 6.10 to 8.50. Two A++ units can differ substantially, so compare the number, not just the class.

Three climate zones for heating

For heating, the label uses three reference climates: average (design temperature −10 °C), warmer (+2 °C) and colder (−22 °C) ¹. The label shows the heating class for the average and the warmer climate ². For most of the UK, the average climate is the realistic one; the warmer figure looks better but reflects southern Europe.

The label also gives the design load for heating (Pdesignh) in kW – the output the unit is sized to deliver at the design temperature ¹. If you want to heat with the unit, that figure is more useful than the higher nominal output in the brochure.

Portables and monoblocks: a different scale

Single-hose portables (single duct) and units with two air ducts (double duct, including most wall-mounted units without an outdoor part) are labelled on EER and COP under standard conditions, not seasonally ¹. A portable rated A+ is therefore not comparable with a split system rated A+.

What does a better class save?

A worked example using the Ofgem price cap unit rate for electricity from 1 October to 31 December 2026: 26.32p per kWh (GB average, Direct Debit) ³.

Cooling. Suppose the unit has to remove 1,000 kWh of heat over a summer:

Heating. Suppose the unit delivers 4,000 kWh of heat over a winter:

The heat quantities are assumptions to illustrate the difference; your own use depends on the building, how you use it and the weather. The lesson is general, though: the UK has relatively few cooling hours, so differences in SEER matter less financially than differences in SCOP. If you will heat with the unit, prioritise a high SCOP.

What else is on the label?

The label also shows annual energy consumption (calculated from a fixed number of operating hours, so it is a comparison figure, not a forecast) and the sound power levels of the indoor and outdoor units in dB(A) ¹. The outdoor sound power level is what your installer uses for the MCS 020(a) noise assessment that permitted development in England relies on.

Is a new label coming?

The European Commission is revising the EU labelling rules for air conditioners and air-to-air heat pumps. Its June 2026 report still lists the revision as “in preparation”, with no entry-into-force or application date ⁴. Whether and when Great Britain follows any new EU label is a separate decision. For now the A+++ to D scale stays.

Checklist for comparing models

1. Compare SEER and SCOP as numbers, not just the class.
2. For heating, use the SCOP for the average climate.
3. Check Pdesignh if you want to heat with the unit.
4. Compare indoor sound power (bedrooms!) and outdoor sound power (neighbours).
5. Only compare portables with other portables.

If heating is your main goal, compare air-to-water heat pumps in our heat pump overview.