Costs and running · 6 min read
SEER and SCOP Ratings Explained
Two acronyms decide most of your running cost. Once you can read them, comparing quotes becomes straightforward.
Published 2026-07-20 · Updated 2026-07-20 · WDI Group (Surrey) Ltd
What the acronyms mean
SEER is Seasonal Energy Efficiency Ratio — cooling output divided by electrical input across a representative season. SCOP is Seasonal Coefficient of Performance, the same idea for heating.
EER and COP are the non-seasonal versions, measured at a single test condition. Seasonal figures are more useful because they reflect part-load running, which is how the unit actually spends its life.
What good looks like
A SEER of 6 means six units of cooling per unit of electricity. Quality domestic units commonly sit between 6.0 and 8.5. SCOP figures around 4.0 to 5.2 are typical for the same equipment in heating.
Energy labels bundle these into A to A+++ bands. Two units in the same band can still differ, so look at the underlying number.
- SEER 6.0+ is a solid domestic system
- SEER 7.5+ is at the efficient end of the market
- SCOP 4.0+ means genuinely cheap heating
Comparing quotes fairly
Efficiency figures are quoted per model and per capacity, so a 2.5kW unit and a 5.0kW unit from the same range will not match. Compare like for like: same capacity, same series, same test standard.
A cheaper quote using a lower-efficiency range can cost more over ten years than the difference on the invoice.
Installation quality changes the real figure
Lab ratings assume correct refrigerant charge, clean coils, sensible pipe runs and unobstructed airflow. A well-specified unit installed badly will never reach its label.
That is why we care about pipe length, outdoor unit position, brazing under nitrogen, evacuation and commissioning readings — they are the difference between a rating and a result.
Frequently asked questions
- Which matters more, SEER or SCOP?
- In a British home, SCOP usually matters more, because most systems end up doing more hours of heating than cooling across the year.
- Do the ratings appear on my quotation?
- Yes. We list model numbers and their published efficiency figures so you can check them independently.