How to choose energy-efficient commercial air conditioning
Updated 23 October 2026 · SEO Dons Editorial
What do SEER, SCOP, EER and COP measure?
EER and COP are single-point ratios. The rated energy efficiency ratio (EER) is the declared cooling capacity divided by the rated power input when the unit is providing cooling at standard rating conditions, and the coefficient of performance (COP) is the equivalent for heating.
SEER and SCOP are seasonal. The ecodesign rules define SEER as "the overall energy efficiency ratio of the unit, representative for the whole cooling season", calculated as the reference annual cooling demand divided by the annual electricity consumption for cooling. SCOP is the heating equivalent. The calculation method is specified in BS EN 14825, which BSI says covers "the temperatures, part load conditions and the calculation methods" for SEER and related seasonal figures. It does not cover single duct, double duct, control cabinet or close control units, so server-room precision units are rated differently.
Why does part-load performance matter more than the headline figure?
A building rarely runs at full load, so the test weights performance across a range of outdoor temperatures instead of rating one point. It also assumes how long the unit works. The ecodesign rules define equivalent active mode hours for cooling as the assumed annual number of hours the unit must provide the design load, and the table of operational hours sets that at 350 hours a year for cooling.
That is an assumption, not a forecast. A shop, office or comms room that cools for many more hours than 350 equivalent full-load hours will use more electricity than the label implies, and a better SEER will save more kilowatt-hours in absolute terms. The test also builds in the "degradation of the energy efficiency caused by on/off cycling", which is one reason the seasonal figure is more useful than a rated one.
What is the legal minimum efficiency?
Two retained regulations set the floor. Regulation 206/2012 covers electric air conditioners with a rated capacity of 12 kW or less. From 1 January 2014 it requires, for units other than single and double duct, the minimum seasonal figures below, which vary with size and with the refrigerant's global warming potential (GWP).
| Rated capacity and refrigerant | Minimum SEER | Minimum SCOP (average season) |
|---|---|---|
| Under 6 kW, GWP above 150 | 4.6 | 3.8 |
| Under 6 kW, GWP 150 or below | 4.14 | 3.42 |
| 6 to 12 kW, GWP above 150 | 4.3 | 3.8 |
| 6 to 12 kW, GWP 150 or below | 3.87 | 3.42 |
Regulation 2016/2281 covers cooling products up to 2 MW, which takes in larger air conditioners and comfort chillers. It uses seasonal space cooling energy efficiency (ηs,c), expressed as a percentage. From 1 January 2021 the minimums include 189% for electric air-to-air air conditioners other than rooftop units, 161% for air-to-water chillers under 400 kW and 179% at 400 kW and above, and 200%, 252% and 272% for water or brine-to-water chillers in its three size bands. The regulation excludes custom-made products assembled on site on a one-off basis.
Do not compare a percentage with a SEER directly. The regulation calculates ηs,c as SEER divided by a conversion coefficient of 2.5, corrected for temperature control. Ask the supplier to declare both. Check the current text on legislation.gov.uk before relying on any figure.
What does the energy label show for units up to 12 kW?
The retained labelling regulation (626/2011) applies to electric mains-operated air conditioners with a rated capacity of 12 kW or less. Its energy classes are set by SEER and SCOP bands:
| Class | SEER band | SCOP band |
|---|---|---|
| A+++ | 8.50 or more | 5.10 or more |
| A++ | 6.10 to under 8.50 | 4.60 to under 5.10 |
| A+ | 5.60 to under 6.10 | 4.00 to under 4.60 |
| A | 5.10 to under 5.60 | 3.40 to under 4.00 |
| B | 4.60 to under 5.10 | 3.10 to under 3.40 |
| C | 4.10 to under 4.60 | 2.80 to under 3.10 |
| D | 3.60 to under 4.10 | 2.50 to under 2.80 |
Classes E, F and G cover lower values still. Put the two tables side by side and the legal floor is easy to read: a SEER of 4.3 is class C, and 4.6 is the bottom of class B. The label ranks units against each other. It is not a quality mark.
What should you ask for on larger VRF and chiller plant?
Above 12 kW there is no equivalent label in the regulations cited here. Ask instead for the declared seasonal figure and for the evidence behind it:
- The exact combination. For multi-split units, the ecodesign rules say each outdoor unit model must have a list of recommended combinations with compatible indoor units in its technical documentation, and that the list "shall be made available prior to the purchase/lease/hire of an outdoor side unit". For multisplit units up to 12 kW, declared data are provided at a capacity ratio of 1, so ask how the quoted combination compares with that.
- The capacity control type: fixed, staged or variable.
- Part-load figures at more than one outdoor temperature, not only the rated point.
- An independent benchmark. The Government's Energy Technology List says every listed product is "placed in the top 25% of the market for energy efficiency in their class". Its air-to-air category covers single split, multi-split and VRF products. The enhanced capital allowance linked to the list ended in April 2020, and the list now serves as a procurement tool for purchasers.
What does a better SEER save in a year?
This is illustrative arithmetic, not a forecast. Suppose a hypothetical building needs 20,000 kWh of cooling delivered over a year. Electricity used is roughly cooling delivered divided by the seasonal efficiency ratio. The formal definition also adds standby, off-mode and crankcase-heater consumption, so real figures are a little higher.
| Unit | SEER | Electricity used (kWh a year) | Saving against the 4.3 floor (kWh) |
|---|---|---|---|
| Legal floor, 6 to 12 kW | 4.3 | about 4,650 | none |
| Bottom of class A | 5.1 | about 3,920 | about 730 |
| Bottom of class A++ | 6.1 | about 3,280 | about 1,370 |
That is about 16% less electricity at SEER 5.1 and about 30% less at 6.1. To put a price on it, multiply the kilowatt-hours saved by the unit rate on your own electricity bill. The air conditioning running costs guide covers pricing, and the saving only pays back if it outweighs any extra purchase cost over the life of the plant.
What matters more than the label?
- Sizing. Government inspection guidance says an assessor will highlight opportunities to replace "older, less energy efficient systems, or oversized systems". See how to size commercial air conditioning.
- Controls. The ecodesign calculation corrects ηs,c for temperature control, so controls are part of the efficiency picture, not an add-on. Air conditioning controls for offices covers the options.
- Installation conditions. Declared figures describe the unit as tested. Ask the designer which pipe lengths, heights and indoor-unit combinations the design assumes.
- Commissioning. In England, where Part L applies to the work, the installer must give building control a notice that the fixed building services have been commissioned using an approved procedure. See what a proper handover includes.
Pulling these together is the job of a specification. The commercial air conditioning guide shows where each item fits, and readers can send an enquiry through the site's form to get help drawing one up.
Sources
- Legislation.gov.uk (Crown), Commission Regulation (EU) No 206/2012: annex I and annex II, as retained in Great Britain, checked 22 October 2026.
- Legislation.gov.uk (Crown), Commission Regulation (EU) 2016/2281: article 1, annex I, annex II and annex III, as retained in Great Britain, checked 22 October 2026.
- Legislation.gov.uk (Crown), Commission Delegated Regulation (EU) No 626/2011: article 1 and annex II, as retained in Great Britain, checked 22 October 2026.
- BSI, BS EN 14825:2022 and BS EN 14825:2018 catalogue entries, checked 22 October 2026.
- DESNZ, Energy Technology List (GOV.UK) and air to air heat pumps, split, multi-split and VRF, checked 22 October 2026.
- GOV.UK (MHCLG), A guide to air conditioning inspections, checked 22 October 2026.
- Legislation.gov.uk (Crown), The Building Regulations 2010, regulation 44, checked 22 October 2026.
Common questions
Is a higher SEER always worth paying for?
Not automatically. The kilowatt-hours saved scale with the hours the system runs and the unit rate you pay, so a system used for few hours may take much longer to justify a higher specification. The arithmetic above shows how to test it for a particular building.
Does the energy label apply to VRF systems?
The labelling regulation covers electric air conditioners of 12 kW or less. Larger plant falls under the ecodesign rules for cooling products up to 2 MW, where the seasonal cooling efficiency has to be declared in the technical documentation. Ask for that declared figure.
Where can I find a unit's declared efficiency?
In the product's technical documentation, which the ecodesign regulation says must carry the declared figures. Compare like with like: SEER with SEER, and percentage efficiency with percentage efficiency.
Which edition of BS EN 14825 should a data sheet quote?
BSI lists the 2022 edition, published 31 August 2022, as current. The 2018 edition is shown as withdrawn on 23 August 2022, so a data sheet that still cites only 2018 may predate the change. Ask the supplier which edition the declared figures used.
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