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Understand What is ISEER and Star Labeling of Inverter Air Conditioners in India

By on April 22, 2016

A few years back when Inverter ACs were introduced in Indian markets, there was a lot of skepticism about their success in Indian conditions. Although they are quite successful and popular internationally, these ACs did have to go through the tests of Indian consumers. Despite some negative rumors by a section of the market, Inverter ACs have come out with flying colors and have become popular in India. One thing that everyone knows (and many have observed) is that Inverter ACs save “HUGE” amount of electricity. But one question has been there in everyone’s mind: Why is there no BEE star rating for Inverter ACs as available for fixed speed ACs? In the year 2015, BEE did provide answer to the question by starting a Star Rating labeling system for Inverter Air Conditioners. With this post, we will try to answer few questions that people have regarding the new Star Rating for Inverter Air Conditioners.

Why Did Inverter ACs Not Have Star Rating Earlier?

Although purpose of any air conditioner is to cool the space, the way cooling happens in fixed speed ACs is different from the way it happens in Inverter ACs. The technology is a bit different. Fixed Speed ACs have fixed cooling capacity (or tonnage) and fixed input wattage, Inverter ACs have varying cooling capacity and input wattage. The definition of efficiency for a fixed speed AC was quite simple:

EER (or COP) = Output Wattage (or cooling capacity) ÷ Input Wattage.

(EER Stands for Energy Efficiency Ratio & COP stands for Coefficient of Performance)

By calculating EER/COP of fixed speed ACs and defining fixed ranges, BEE was able to divide all the fixed speed models in the market in 5 groups of different star ratings. But this works well when there is fixed output wattage and fixed input wattage. But defining the same for Inverter AC was very difficult as both the input and output wattages vary.

What Will Be The Method To Define Star Rating Now?

World over the method of defining energy efficiency of air conditioners is not EER (Energy Efficiency Ratio), but it is SEER (or Seasonal Energy Efficiency Ratio). The basic theory behind SEER is that the temperature does not remain the same round the year. As there is seasonal variation of temperatures, there is variation in the amount of cooling required. Amount of energy (or electricity) required by an air conditioner to cool a room to 25 degrees (or any other standard temperature) is different when outside temperature is 30 degrees in comparison to when the temperature is 40 degrees. Also the usage (in hours per day) would vary as per the seasons.

SEER calculation thus involves defining annual temperature profile and usage patterns. SEER standards have to be different for different countries as every country has a different climate profile. And thus BEE has defined Indian SEER or ISEER in short. Let’s look at the various terminologies used as part of the definition:

  1. Cooling Seasonal Energy Consumption (CSEC) – Total annual amount of energy (electricity) consumed by the equipment when it is operated for cooling in active mode.
  2. Cooling Seasonal Total Load (CSTL) – Total annual amount of heat that is removed from the indoor air when the equipment is operated for cooling in active mode.
  3. Indian Seasonal Energy Efficiency Ratio (ISEER) – 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.

To calculate the total annual electricity consumption the assumption used is that the Air Conditioner will be used for 1600 hrs through the year. Annual temperature profile used is based on weather profile for 54 cities across India. Below is the temperature distribution used:


The ISEER thus calculated will be used to provide star ratings to various models of air conditioners. Below are the defined ranges of ISEER for various star ratings:


What Information Will You Get From Manufacturers?

A lot of what is mentioned above is technical jargon. For an average consumer the most important thing to know is to understand the information provided by the manufacturers. Here are the things that will be available from the manufacturers:

  1. Rated Cooling Capacity (100% Load): This is the marketing tonnage or marketing cooling capacity. Inverter Air Conditioners have variable cooling capacity and a 1 ton inverter AC may vary its tonnage from 0.2 ton to 1.2 ton. But they are marketed as 1 ton inverter AC. Rated Cooling capacity for a 1 ton inverter AC would be 1 ton. As per BEE standards there is a tolerance of ± 5% for this value.
  2. Rated Cooling Capacity (50% Load): BEE has asked manufacturers to provide power consumption at 50% capacity. This is not the minimum cooling capacity, but the 50% of the total capacity. In case of 1 ton AC it would be 0.5 ton. But this does not mean that it cannot go below 0.5 ton.
  3. Maximum Cooling Capacity: This is the maximum cooling capacity. As in the example above of 1 ton, it would be 1.2 ton.
  4. Rated Power Input (100 % load): This is power consumption in watts when the AC runs at 100% load or at the marketing tonnage.
  5. Half Power Input (50 % load): This is power consumption in watts when the AC runs at 50% load or at the marketing tonnage.
  6. Maximum Power Input: This is power consumption in watts when the AC runs at the maximum tonnage that the Air Conditioner can achieve.
  7. Cooling Seasonal Energy Consumption (in kWh): This is the annual power consumption as measured per BEE standards mentioned above. Please note, that this number is for 1600 hrs and actual number for you will depend on your usage and temperature of your city when you use the AC.
  8. ISEER: This is the ratio of total heat removed and total energy consumed. This is the ideal number to compare two ACs as your usage of AC may vary and thus the electricity consumption may not be the same as the number mentioned in Cooling Seasonal Energy Consumption.

How Does Star Rating Of Inverter ACs Compare With That Of Fixed Speed ACs?

Comparing the Star Ratings of ACs across segments (window, split and Inverter) has been the biggest source of confusion for most consumers. Unfortunately the standards that have been defined do not help remove the same. The concept of ISEER can be used for fixed speed ACs as well, but from what we know as of now, it will not be used. The rating standards of fixed speed ACs will remain the same based on EER.

However from what we have seen, even a BEE 2 or 3 star rated inverter AC would be equivalent or better than BEE 5 star rated split AC of fixed speed type. And any inverter AC would be much better than any window AC.

Has BEE Started Rating New Inverter AC Models?

The new standards are voluntary till the end of 2017. Which means, manufacturers can sell AC models with or without star rating till end of 2017. As star ratings for ACs are quite popular amongst the masses, many manufacturers will try to get their models certified by BEE, but it is also possible that you may get models that are not rated. It will be beneficial for consumers if they start insisting on star rating and demanding manufacturers to sell only star rated ACs.

When Will BEE Make It Mandatory For All Inverter AC Models To Be Star Rated?

From the year 2018 onwards, all models of inverter ACs will have to be star rated. Manufacturers will not be able to sell non-star rated inverter ACs.


Star Rating labels for Inverter ACs is a welcome move by BEE. Inverter ACs have raised the bar for energy efficiency of air conditioners in India and labelling will further improve the efficiency. The future looks bright and soon air Conditioners will not be a big strain on electricity bills.

About the Author:
Abhishek Jain is an Alumnus of IIT Bombay with almost 10 years of experience in corporate before starting Bijli Bachao in 2012. His passion for solving problems moved him towards Energy Sector and he is keen to learn about customer behavior towards Energy and find ways to influence the same towards Sustainability. .