What is ISEER Rating? EER vs SEER vs ISEER

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If you look at your air conditioner’s “power saving guide” label you will find the ISEER rating written on it

But have you wondered what this rating depicts.

ISEER full form is Indian Seasonal Energy Efficiency Ratio

Also, there are other terms that can be found related to ACs that are EER and SEER ratings.

In simple terms, all these ratings tell how energy efficient an AC is.

Efficiency = Output / input

For AC the output is Cooling and the input is power consumed or electricity consumed.

These various ratings differ from each other by test conditions

It all started from EER rating.

What is EER Rating ?

EER stands for Energy Efficiency Ratio

It is the efficiency of an air conditioner tested with constant outdoor and indoor temperature in the season of summer when the temperature is at peak

For EER rating, indoor and outdoor both temperatures are fixed.

How is it calculated?

EER is calculated at a 35 °C outside temperature while the indoor temperature is at 26.6 °C with 50% relative humidity.

The cooling output is measured in British Thermal Units (BTU) while the electricity input is in Watt Hours

EER rating = Capacity (in BTU) / Power (in Watts)

Let’s take an example of 1 Ton AC,

A 1 Ton AC can cool a room with 12,000 BTUs of power and suppose it consumes 1,200 Watt-hours of electricity. 

In this case, dividing the BTUs by the Watt-hours, the EER rating will be 10

What is SEER Rating ?

SEER stands for Seasonal Energy Efficiency Ratio

Similar to the EER rating, it is the ratio of the cooling output of an AC to the power consumption. But unlike EER which is calculated on the peak hot days of summer. This is calculated over the entire summer season

Problem with EER rating

The outdoor temperature changes throughout the entire summer season and does not remain the same

For example in Delhi, 

The summer season spans from May to August. 

And temperature may go from 32-38 °C in May to 40-45 °C in June, July and again 32-38 °C in august. 

So SEER rating came in which the air conditioner is tested in the entire summer season with varying outdoor temperature. The various values calculated are averaged out to give the value of SEER

How is SEER calculated ?

This rating is calculated by measuring the average EER over a range of outdoor temperatures from 18.3 °C to 40 °C with constant indoor temperature

It is like an averaged value while EER is calculated only on the hottest days of summer.

What is ISEER Rating

ISEER stands for Indian Seasonal Energy Efficiency Ratio

ISEER is the ratio of the total annual amount of heat that the equipment can remove from the indoor air when operated for cooling in active mode to the total annual amount of energy consumed by the equipment during the same period.

It is specific to the Indian region.

Problem with SEER Rating

SEER rating is calculated to provide efficiency rating specific to weather in the middle of the United States. 

India has a wide variety of seasons and the temperature varies from place to place. 

So the Bureau of Energy Efficiency (BEE) made its own rating called ISEER rating which is specific to the Indian region.

ISEER measures the energy efficiency of air conditioners based on a weighted average of the performance at outside temperatures between 24 and 43 degree C based on Indian weather data

The ISEER rating was made mandatory in 2018 and now every AC has this rating on it.

The Bureau of Energy Efficiency (BEE) divides each AC into a category by star rating based on its ISEER value.

This rating changes with time.

The below ratings are the proposed star rating for split ACs from 2020 to 2021

proposed star rating for split ac  from 2020 to 2021

Higher the ISEER rating, the better the cooling efficiency.

You can check our list of highest iseer rating ac in India. The number 1 pick consumes half electricity from average aircon in the market.

What to look for when purchasing AC

When purchasing AC first decide the tonnage according to your room size.

AC ton based on the room size

Room Size (square feet)Ton
Size < 1201 ton
Size > 120 & Size < 1801.5 ton
Size > 180 & Size < 2602 ton

Then decide which type of AC you need – window or split

Always buy the latest model.

Then check the BEE star rating along with the ISEER rating, higher the ISEER rating the better.

Benefits of Higher ISEER rating

  • Better Cooling Efficiency
  • Reduced Electricity Bills

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