SEER (Seasonal Energy Efficiency Ratio) is the ratio between the useful cooling an air conditioner delivers over a reference season and the electricity it consumes to produce it, defined by Regulation (EU) No 206/2012 and measured under the EN 14825 standard. It is therefore a seasonal figure, not an instantaneous one: EER only holds for a single operating point. Regulation (EU) No 626/2011 requires SEER on the energy label of air conditioners up to 12 kW, where a SEER of 8.5 or more earns class A+++.
SEER: definition and calculation under EN 14825
Four part-load points over a reference season
SEER does not come from a single test. The EN 14825 standard runs the machine at four outdoor temperatures, with the room held at 27 °C (19 °C wet bulb), and at a load that falls as the outdoor heat drops: that is how an air conditioner really works, almost never flat out.
| Test point | Outdoor temperature | Load required |
|---|---|---|
| A | 35 °C | 100% |
| B | 30 °C | 74% |
| C | 25 °C | 47% |
| D | 20 °C | 21% |
The EERs measured at these four points are interpolated over each temperature bin of a reference cooling season (17 to 40 °C), then weighted by the number of hours in each bin: that gives the active-mode SEER. Regulation (EU) No 206/2012 then adds what the machine consumes without producing cooling (thermostat satisfied, standby, crankcase heater, off mode), on a conventional basis of 350 full-load equivalent hours a year. The SEER displayed is the reference annual cooling, i.e. the rated cooling output × 350 h, divided by the total annual consumption.
That explains the gap that surprises clients: an inverter split often shows a SEER of 6 to 8 for an EER at 35 °C half as high, because its slowed compressor works with heat exchangers that are proportionally larger at part load.
What SEER does not cover
The SEER on the label covers air-cooled air conditioners up to 12 kW, splits and multi-splits. A single-duct or double-duct portable unit has none: its label shows only an EER, measured at a single point, and so impossible to compare with a SEER. Above 12 kW, air conditioners fall under Regulation (EU) 2016/2281, which works in seasonal efficiency expressed in primary energy (ηs,c, in %) rather than a SEER on a label. Finally, SEER says nothing about output: read it alongside the rated cooling capacity.
Converting SEER into consumption: formula and worked example
The conversion fits on one line: electricity consumption (kWh) = cooling need (kWh) / SEER. All the work is in the numerator. The label uses a conventional basis (rated output × 350 h); on a job, the real need depends on solar gains, insulation, the setpoint and occupancy hours.
Example for a 3.5 kW split, on the label's basis: 3.5 × 350 = 1,225 kWh of cooling a year. The cost is calculated at €0.20/kWh, an order of magnitude for household electricity in France, to be adjusted to the client's contract.
| SEER (class) | Electricity consumed | Indicative annual cost |
|---|---|---|
| 4.6 (B, legal floor) | 266 kWh | €53 |
| 5.6 (A+) | 219 kWh | €44 |
| 6.1 (A++) | 201 kWh | €40 |
| 8.5 (A+++) | 144 kWh | €29 |
Two readings for the quote. First, the gap between A++ and A+++ is worth around ten euros a year on this basis: on its own, it does not pay back a large equipment premium in a house in northern France where the air conditioning runs for a few weeks. Second, the calculation changes scale as the hours lengthen: in the south (zone H3), in a home poorly shaded from the sun or with home working, the need can double and the gap with it. The lever that really shrinks the numerator remains solar protection and night-time ventilation, before the choice of class. On a reversible unit, run the same calculation in heating with the SCOP, which often weighs more on the bill: the method is set out in our article on the SCOP and COP of a heat pump.
SEER: what this indicator really says about air conditioning performance
The difference between SEER and electricity consumption: don't confuse performance and the bill
SEER measures seasonal efficiency in cooling mode. It's a ratio between the cooling produced and the electricity consumed, calculated over a typical season under standardised conditions. The higher it is, the more efficient the air conditioning is for comparable use. But your bill also depends on operating hours, the setpoint, insulation and solar gains.
SEER, output, floor area: how to avoid miscalculations on site
A good SEER doesn't replace proper sizing. Floor area alone is quickly misleading. Check the cooling output (kW) and the actual needs. Exposure, glazing, attic, occupancy and volumes all change things. Oversizing causes cycling, hampers dehumidification and can degrade real-world efficiency. Undersizing leaves the compressor running flat out. To go further, see our guide on calculating cooling output for air conditioning.
SEER and reversible air conditioning: what changes in heating mode
For a reversible unit, heating is better assessed with the SCOP and the output available at different outdoor temperatures. SEER remains useful for comparing cooling, but it says nothing about defrosting, cold-weather performance, or shoulder-season comfort. On a quote, ask for both indicators.
How to read a product sheet: identifying the SEER of an air conditioner without getting it wrong
Where to find the SEER (energy label, manual, manufacturer documentation)
On the energy label, look for the SEER line or the mention of "seasonal cooling efficiency." On a reversible air conditioner, the value appears next to the SCOP. You'll also find it in the manufacturer's technical datasheet, sometimes called an "ErP sheet" or "datasheet," and in the installation manual. A catalogue that already carries the verified characteristics of each range saves you hunting for it machine by machine. Check that the value matches cooling mode and the correct pairing (indoor unit plus outdoor unit).
SEER, SCOP, EER: what each value is used for in judging performance
SEER is used to estimate consumption over a cooling season. The higher it is, the better the efficiency. SCOP plays the same role for heating (useful if the unit is a heat pump). EER, meanwhile, corresponds to efficiency measured at one specific operating point. Handy for comparing under identical conditions, but less meaningful over a full year.
Energy classes and SEER: interpreting the gaps between models
The energy class in cooling mode is derived from the SEER. A class difference often reflects a real jump in consumption, but always compare similar outputs and the same configuration (single-split, multi-split). To decide, keep a simple benchmark in mind: class + SEER beat a marketing promise. And be wary of a class obtained on a configuration that is not yours: the label of a single-split says nothing about the same model run as a multi-split.
The boundaries are not a trade convention, they are set in Annex II of Delegated Regulation (EU) No 626/2011 for air conditioners below 12 kW other than single and double duct units.
| Class | SEER, cooling mode | SCOP, average heating season |
|---|---|---|
| A+++ | ≥ 8.50 | ≥ 5.10 |
| A++ | 6.10 to 8.50 | 4.60 to 5.10 |
| A+ | 5.60 to 6.10 | 4.00 to 4.60 |
| A | 5.10 to 5.60 | 3.40 to 4.00 |
| B | 4.60 to 5.10 | 3.10 to 3.40 |
| C | 4.10 to 4.60 | 2.80 to 3.10 |
| D | 3.60 to 4.10 | 2.50 to 2.80 |
| E | 3.10 to 3.60 | 2.20 to 2.50 |
| F | 2.60 to 3.10 | 1.90 to 2.20 |
| G | < 2.60 | < 1.90 |
A regulatory floor sits underneath those classes: since 1 January 2014, Regulation (EU) No 206/2012 has barred from the market any split unit below 6 kW with a SEER under 4.60 and a SCOP under 3.80, thresholds lowered to 4.14 and 3.42 where the refrigerant has a GWP of 150 or less. A machine sold as "class B" is therefore sitting on the legal floor rather than near the top of the range, and that is a distinction to make at the refrigeration engineer's quotation stage rather than at handover.
Difference between SEER, EER, SCOP and COP: which to look at, and where
The four figures travel on the same documents and are easily confused. They do not answer the same question, and quoting the wrong one shows.
| Figure | What it measures | Over what period | Where you read it |
|---|---|---|---|
| EER | cooling efficiency at one operating point | instantaneous, fixed test conditions | detailed technical sheet |
| SEER | cooling efficiency across a full season | seasonal, several temperatures and part loads | energy label and product sheet |
| COP | heating efficiency at one operating point | instantaneous | detailed technical sheet |
| SCOP | heating efficiency across a full season | seasonal, weighted by a reference season | energy label and product sheet |
The habit to keep: on a reversible unit the client almost always compares SEER, while actual use may be mostly heating. On a unit fitted in a cool maritime climate and run for three weeks of cooling a year, it is SCOP that will drive the bill. Quote both, or you get corrected at the first winter.
What the energy assessment does with SEER, and the default-value trap
An energy performance assessment computes a conventional annual consumption. It aggregates mainly heating and hot water, and includes cooling where a system exists: SEER then drives the estimated electricity of that item. Do not confuse it with the summer comfort indicator, which is reported separately and is about far more than the presence of air conditioning.
The expensive point lies elsewhere. The method is highly sensitive to the data entered, and where documents are missing the assessor applies default values, and those defaults are penalising. In other words, a high-performing machine that is poorly documented will be scored as a mediocre one. What you hand over at completion therefore decides the client's rating: technical sheet, manual, make and output of the indoor units, a description of the controls, proof of servicing. Controls weigh as much as SEER on the outcome, which is worth explaining at quotation stage rather than at assessment stage. On how the method itself is changing, see the new rules of the 2026 energy assessment.
Why real SEER falls short of the label
Two machines identical on paper do not perform the same in a dwelling, and the gap never comes from the product. It comes from four causes, all of them on your side.
| Cause | Effect on performance | What to check before pricing |
|---|---|---|
| Oversizing | short cycling, efficiency lost in the shoulder seasons | size on heat loss and gains, not on floor area |
| Insufficient airflow | degraded exchange at the evaporator | duct sizing and routing, accessible filters |
| Poorly ventilated outdoor unit | degraded condensing, consumption up | clear air intake, clearances, condensate drainage |
| Imperfect refrigerant charge | performance down across the whole range | pipe run length, added charge, leak check |
The first one does the most damage, and it is also the hardest to sell, because the client hears "bigger is safer". The sizing method is set out in our article on calculating cooling capacity.
SEER and client comfort: translating air conditioning performance into concrete benefits
Noise, control, variable speed: criteria to weigh alongside SEER
A high SEER indicates good seasonal efficiency. But, for the client, comfort also depends on noise comfort, control quality and a variable-speed compressor. Ask for the dB(A) level at minimum output, temperature stability and the ability to modulate without on/off cycling.
Poor setup, maintenance, fouling: when real-world performance drops despite a good SEER
An air conditioner can show a good SEER on the label and still underperform on site. Poorly set airflow, an approximate refrigerant charge, fouled filters and heat exchangers. With regular maintenance and careful commissioning, you limit excess consumption, reduced airflow and client complaints.
Air conditioning during a heatwave: practical limits and points to watch
During a heatwave, the machine isn't the only limiting factor. Solar gains, insulation, shutters and night-time ventilation matter just as much. Aim for a realistic setpoint (a moderate gap with the outdoor temperature), avoid blowing air too cold, and make sure sizing, defrosting and condensate drainage are all secure. To reduce overheating even before talking about equipment, also see passive solutions before air conditioning.
Choosing air conditioning well in 2026: using SEER to compare and quote
Single-split, multi-split, ducted: the impact on SEER and overall performance
SEER measures seasonal efficiency in cooling. The higher it is, the less the air conditioning consumes for equal comfort. Compare at comparable output and on the same energy label. In practice, a single-split often shows a more favourable SEER. A multi-split can see its efficiency drop if several units run at the same time. A ducted system brings comfort, but network losses and poor settings can eat into real-world performance. On a multi-split, require the SEER declared for the combination of indoor units actually installed, not that of the outdoor unit alone; choosing the number of units is covered in our article on multi-split and how many splits per home.
Sizing and installation quality: what wins (or loses) performance
An oversized unit cycles on and off. It cools quickly, then shuts off, starts again. The result: more kWh and less dehumidification. Good sizing, an accurate refrigerant charge, well-insulated connections and clean condensate drainage keep your efficiency at the level of the advertised SEER.
Quote talking points: explaining SEER to the client without jargon
Simply put, SEER is a "frugality score" for the year. Example: for similar use, a SEER 8 model consumes 25% less than a SEER 6 model (6 / 8 = 0.75). You can put a number on it. Estimated consumption = cooling kWh / SEER. Like good glazing, it lets comfort through, not the bill.
Frequently asked field questions about SEER in air conditioning
Is a high SEER enough to guarantee good performance?
No. A good SEER gives a trend on seasonal efficiency in the lab, but on site the air conditioning's performance mainly depends on proper sizing, installation, the tightness of the connections, and settings. A very highly rated unit can still overconsume if it's oversized or if maintenance is neglected. The installation makes the difference.
What SEER should you aim for in air conditioning, depending on use?
In residential settings, aim for at least class A++ in cooling (SEER ≥ 6.1), and move up the range as running hours lengthen: that is where a SEER gap turns into euros. In light commercial use, look for a high SEER, but also check the controls and part-load operation. Actual use before the catalogue.
| Situation | SEER to aim for | Why |
|---|---|---|
| Back-up a few weeks a year (zones H1, H2) | ≥ 5.6 (A+) | few hours, the bill gap stays at a few euros |
| Typical residential | ≥ 6.1 (A++) | good balance between purchase price and consumption |
| Intensive use, zone H3, home working | ≥ 7, ideally ≥ 8.5 (A+++) | the cooling need doubles and the SEER gap with it |
| Reversible unit heating in winter | SCOP first, then SEER | heating often weighs more than cooling |
SEER and grants: what you can safely tell clients in 2026
State it plainly. A good SEER can reduce consumption, but it isn't enough on its own to open the door to a grant. Cooling-only air conditioning gets no grant. A reversible air-to-air heat pump is not eligible for MaPrimeRénov': the per-measure route, narrowed since 1 September 2026 by decree No 2026-822, does not cover it. It does, however, fall under CEE operation sheet BAR-TH-129, whose performance criterion is the SCOP (at least 3.9 up to 12 kW), not the SEER. How a reversible unit works and what grants it can get are covered in our article on reversible air conditioning. To frame what you can tell your clients, rely on a practical guide to CEE and MaPrimeRénov' grants.
