SEER calculator
SEER averages a whole season, not a single moment.
Your inputs
Your inputs are processed on your device and are not sent to a server.
Example loaded. You can change any value.
There is no figure yet: nothing is calculated until you ask for it.
- Enter your measurements.
- Check the units and the assumptions.
- Press Calculate, or load the example.
Rather see a worked case? Press “Load example” and change any value afterwards.
Next step
SEER only shows up in the bill: it is worth seeing it as money per month.
Where each number comes from Conversion constants are exact; densities and coverage rates come from cited sources; everything else is an assumption you can change. Methodology · Sources and updates
How to use it
- Choose whether you are working out the SEER or estimating seasonal use.
- To work out SEER, enter the cooling produced and the electricity used.
- To estimate use, enter the capacity, the SEER and the equivalent hours.
- The result includes the European-scale equivalent.
How it is calculated
SEER measures the efficiency of a whole season, not a single moment:
This difference from EER is the point: an inverter unit starts, modulates and stops through the summer, and those part-load cycles are usually more efficient than running flat out. SEER captures that; EER does not.
In the United States, labels have used SEER2 since 2023, measured at a higher external static pressure. The same unit shows a slightly lower SEER2 than its old SEER: it has not got worse, it is measured differently.
Worked example
A unit producing 10 million BTU over a season while using 500 kWh:
- Electricity in Wh: 500,000 Wh
- SEER: 10,000,000 / 500,000 = 20 BTU/Wh
- On the European scale: 20 / 3.412 = 5.86
The other way round: a 12,000 BTU/h unit with SEER 20 running 500 equivalent full-load hours uses 12,000 x 500 / 20 / 1,000 = 300 kWh over the season.
Good to know
- SEER and EER are not comparable. A SEER of 20 and an EER of 20 describe different things, even sharing units.
- SEER2 since 2023. New US labels use tougher test conditions; the values come out somewhat lower.
- Equivalent hours are an assumption. No unit runs exactly 500 hours at 100 % capacity: it is a way of estimating.
- Capacity is not consumption. The BTU/h, frigories or kW on a label measure the heat the unit removes from the room, not the electricity it uses. For that you need the efficiency rating or the rated input power.
Frequently asked questions
What is SEER?
Seasonal efficiency: all the cooling produced over a season divided by all the electricity used in that season. The higher it is, the less it costs to run.
What is the difference between SEER and EER?
EER measures one operating point at full load; SEER averages a whole season including starts and part load. SEER is usually higher and describes real running costs better.
What is a good SEER?
It depends on the market and current regulations. As a reference, high-performing domestic units today sit at or above 20 BTU/Wh on the US scale.
What is SEER2?
The test procedure in force in the United States since 2023, using a higher external static pressure. The same unit shows a slightly lower SEER2 than its previous SEER.
Can I estimate a summer's cost from the SEER?
Yes, and that is its best use. You need the unit's capacity and an estimate of equivalent full-load hours for your climate and usage.