The short answer
SEER and SCOP are the seasonal efficiency ratings on an air conditioner's energy label, for cooling and heating. Each shows roughly how much heat the unit moves over a standard season for every unit of electricity it uses, and higher is better.
On this page
The energy label on an air conditioner looks like the ones on fridges and washing machines, but a split system's label carries two ratings side by side, one for cooling and one for heating. The seasonal figures behind them are the most useful efficiency numbers you'll find when comparing units, as long as you know what they measure and what they leave out.
What SEER and SCOP measure
SEER stands for seasonal energy efficiency ratio and covers cooling. SCOP stands for seasonal coefficient of performance and covers heating. Both are ratios: the heat moved over a whole season divided by the electricity used to move it.
A SEER of 7, for example, means that over the standard cooling season the unit moves about 7 kWh of heat out of the room for every 1 kWh of electricity. A SCOP of 4 means about 4 kWh of heat delivered for every 1 kWh used.
"Seasonal" is the important word. The single-point ratings, EER for cooling and COP for heating, measure efficiency at one set of test conditions. The seasonal versions combine results across a range of outdoor temperatures and at part load, where an inverter unit spends much of its time, and they include the small amount of electricity used on standby. That makes them a better guide to how a unit performs across a year. COP and EER explains the single-point figures.
What else the label shows
| On the label | What it tells you |
|---|---|
| Efficiency class | A letter and colour for cooling and for heating |
| SEER and SCOP | The seasonal figures behind each class |
| Design load, in kW | The output the seasonal figures are based on |
| Annual energy use, in kWh | Electricity used in a standard season |
| Sound power, in dB | Noise from the indoor and outdoor units |
The heating figures are based on a standard climate, and some labels show figures for warmer and colder climates as well. The sound power levels are higher than the sound pressure figures quoted in most brochures because they measure something different, and decibels explained covers the difference.
Comparing two units
- Compare the same size. Within a range, larger units often have somewhat lower seasonal figures than smaller ones, so compare a 2.5 kW unit with another 2.5 kW unit.
- Compare the figure, not only the class. Two units in the same class can have noticeably different SEER or SCOP values.
- Weight the rating that matches your use. If you'll mainly cool, SEER matters most. If you'll use the unit to heat through winter, give SCOP more weight.
- Check the pairing. Figures for a split system are measured for a specific indoor and outdoor unit together, so make sure the label matches the combination you're being quoted.
Using the label to estimate running costs
The annual energy figure gives a rough sense of scale. Multiply it by what you pay for electricity: if a label showed 150 kWh a year for cooling, at an example rate of 25p per kWh (check your own tariff), that would come to £37.50.
That figure assumes a standard number of hours of use in a standard season. Your own use could be far higher or lower, depending on how hot it gets, how many hours you run the unit and the temperature you set. How much air conditioning costs to run goes through the method in more detail.
What the label can't tell you
Seasonal figures come from laboratory tests under set conditions. In your home, efficiency also depends on:
- how well the system is installed, including the pipe run and the refrigerant charge
- where the outdoor unit sits, and whether it has enough space around it for air to flow
- how cold it gets in winter, and how often the outdoor unit has to defrost
- whether the unit is the right size for the room
- clean filters and regular servicing
Portable air conditioners with a single or double hose carry a different label, showing single-point EER and COP figures rather than seasonal ones. Their ratings can't be compared directly with a split system's SEER and SCOP.
Related guides
- COP and EER: what efficiency meansCOP (heating) and EER (cooling) compare the heat a unit moves with the electricity it uses, under one set of test conditions. A COP of 3 means 3 kW of heat for every 1 kW of electricity; higher is more efficient.
- How much does air conditioning cost to run?Multiply the electricity it uses, in kWh, by your unit rate. How much a unit uses depends on the room, the weather, the temperature you set and its efficiency, so estimate it from its average power draw and the hours it runs.
- kW and BTU explainedkW and BTU per hour both measure an air conditioner's capacity, meaning how much heat it can move. One kW is about 3,412 BTU per hour, so a 3.5 kW unit is roughly a 12,000 BTU unit.
- Decibels explainedA decibel (dB) is a unit on a logarithmic scale, so adding 10 dB means ten times the sound energy and sounds roughly twice as loud. Air conditioner figures are usually in dB(A), which reflects how sensitive hearing is to different pitches.