EER, ISEER, CoP, BEE Star Rating – All You Need To Know!

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Many of us get confused when we hear some words like ISEER, EER, BEE star rating while we purchase an air conditioner. These are not mere words, rather you may consider these words as technological terms set by the Government.

These technical terms are related to the efficiency of an air conditioner to save energy. In this article, we will clear all the confusion about these technological terms.

This detailed concept about these technical terms will help you to purchase the best air conditioner with all the required knowledge.

Often you have noticed start rating markings when you purchase any electrical appliance. Many of us don’t even know about the concept of BEE star rating, Tonnage, BTU, etc.

As for now, the government has made it easy by stating that a higher star rating is better than a lower star rating. Whenever you invest your hard-earned money in any electric appliance, it’s important to know every detail about it.

This article will shed light on the aspects that govern these star ratings so that you can purchase your air conditioner with some knowledge. Now we will look at some of the jargon used by air conditioner manufacturers.

What is BTU?

BTU stands for British Thermal Unit, that is the unit used to measure thermal energy. Particularly, we can say that it is the amount of energy required to raise 1 pound of water at 1 degree Fahrenheit.

When the term BTU is related to the air conditioning system, the measurement is displayed in terms of how many BTUs per hour of the product can remove or add from the air.

In simpler terms, we can say that 3,412 BTU = 1 kW/hr.


In the market, the tonnage of AC starts from 0.75 ton and it ranges to 2 tons. You must think about what this tonnage means.

Ton is the amount of heat that is removed by the air conditioner in one hour.

In India, the amount of removed heat is measured by the BTU or by the British Thermal Unit. Higher BTU will provide higher cooling capacity.

For example, you can see 1 ton is equal to 12000 BTU/hr and a 2 ton AC unit would be rated at 24,000 BTU/hr.

A ton is the amount of space cooled by 1 ton of ice.

How to Choose the Proper Tonnage of an AC?

It is a high concern among customers how to choose the proper tonnage for the air conditioner. The tonnage of an air conditioner depends on a lot of factors such as the size of the room, the amount of appliances present in the room, the city you are living, etc.

It is also highly dependable on the season. Like you can see than in summer, the weather gets extremely hot in India, so you need a higher tonnage to deal with the heat.

All these factors are related to choosing the proper kind of tonnage for an air conditioner.

Now, you may understand that AC manufacturers try to confuse the customers instead of convincing them. Here also keep in mind that you don’t have to buy an AC just according to the season as you can’t purchase different air conditioners according to different seasons.

Regarding this matter, you can go for Inverter AC. We recommend you if you have a room that requires 1.2 tons of cooling you can go for a 3 star 1.2 ton AC instead of choosing a 5 star 1.5 ton AC.

As over sized air conditioner will cause energy inefficiency.

The following table will help you choose the right size of air conditioner according to the room size.

Size of the Room Recommended AC Size
0 to 80 square feet 0.75 Ton
80 to 120 square feet 1 Ton
120 to 180 square feet 1.5 Ton
180 to 300 square feet 2 Ton

Hopefully, the concept of tonnage is clear to you now. Now we will step further to the other technological term related to an air conditioner.

EER (Energy Efficiency Ratio)

EER defines the amount of heat that the air conditioner removes per hour and it is divided by the power consumed by the machine. It shows that an air conditioner with a higher EER rating ensures higher efficiency.

BEE Star Ratings

For instance, you can see an EER is equal to 27 degree temperature of the inside room and 35 degree temperature outside the room, and the humidity will be 50%.

EER = BTU/hr/Watt.

The EER ratio is measured by the BTU for the cooling capacity and for power inputs it is measured by Watt.

For instance, an air conditioner of 10,000 BTU consumes 1,200 Watts. As per the calculation of 10,000 BTU divided by 1,200 Watts, the rating of this air conditioner is 8.3. You may contact the manufacturer to know the exact size of your air conditioner.

The only difference between SEER and EER is the letter ‘S’ that stands for the seasonal. Therefore an air conditioner with a higher SEER or EER means the higher cooling capacity of the AC with lesser power consumption.

Advantages of the EER Rating

  • The benefit of EER rating is that though EER rated air conditioners cost more while purchasing, it will save a lot of money for the consumer.
  • In such places like big offices, industries where the air conditioners run constantly higher EER rated air conditioners provide huge savings in a short period.
  • The portable air conditioners come with higher EER ratings. These air conditioners also offer the same savings for home usage and huge business sector usage.

What is SEER?

Seasonal Ratio Efficiency or the SEER for air conditioners is a new technique of star rating that was introduced in India on 24th August in 2016. Presently that method is known as ISEER.

In India or another country, the temperature does not remain the same throughout the year. There you will notice seasonal variations in the temperatures. This seasonal variation keeps an impact on the cooling system of an air conditioner.

As a result, the variation in the amount of cooling increases. Here, the SEER calculation defines the yearly temperature profile and the usage patterns to calculate the energy efficiency of an air conditioner.

Difference Between EER and SEER

As we have discussed earlier, both EER and SEER are the measurements of the efficiency of an air conditioner. The higher EER or SEER ensures more efficiency of the AC unit.

  • SEER measures how much energy an air conditioner uses annually, EER, on the other hand, is the most accurate for comparing the two HVAC ( Heating, Ventilation and Air Conditioning) units.

  • The SEER rating of an air conditioner envisaged when we look at the large units for the central air conditioning. On the other hand, EER ratings are envisaged with portable mounted window air conditioners.

  • SEER rated ACs are based on a standard test through a particular seasonal change. On the other hand, EER based air conditioners are used to compare the ACs engineering calculations.

  • As per the units of HVAC, SEER and EER both give importance to the size of the air conditioner as per your room.

The Concept of ISEER

ISEER stands for the Indian Seasonal Energy Efficiency Ratio. ISEER is the measurement of the complete amount of heat that can be removed by an air conditioner from the indoor air. It is measured with the total amount of energy that the AC consumes yearly when it is in the active mode of cooling.

The concept of both SEER and ISEER is same. But here two more factors you have to consider.

CESC: CSEC stands for Cooling Seasonal Energy Consumption. It defines the entire amount of energy or electricity by an air conditioner when it is in the active mode regarding the cooling procedure.

CSTL: CSTL stands for Cooling Seasonal Total Load. It defines the complete yearly amount of heat the air conditioner removes from the indoor room when it gets in the active mode.

Therefore, you can see that ISEER = CSEC/CSTL.

The way to calculate the total annual electricity consumption by the air conditioner is 1600 hours throughout the year. The annual temperature profile depends on the weathering profile of 54 Indian cities.

Benefits of ISEER Ratings

We have discussed earlier, that the higher ISEER ratings in an air conditioner show the higher efficiency of that equipment. You can get several benefits from a higher ISEER rated air conditioner such as,

  • You will get lower utility bills.
  • Your electric appliance will have a good influence on the environment.
  • Such air conditioners with high ISEER rating removes moisture from the air and provides better control over the humidity.

What is CoP?

COP stands for Coefficient of Performance of a heat pump of an air conditioner. The higher CoP ensures lower operating cost and this ratio measures the energy efficiency of the heating performance.

On the other hand, EER measures the energy efficiency of the cooling performance of the air conditioner. Both these jargon are similarly essential to select the best ac in India. CoP is a unit less quantity.

The link between EER and CoP is, EER = 3.412 CoP .

What is BEE?

BEE stands for the Bureau Of Energy Efficiency. It is an agency operated by the Government of India and it was established in March 2002 under the Ministry of Power. BEE is an autonomous Government agency that introduced conservation and efficient usage of energy in some electrical appliances in India.

Star rating with BEE means the capacity of the particular appliance according to the storage volume, volume, and electric consumption per unit.

The most essential thing for an average customer is to understand the information given by the manufacturers. All of the above mentioned jargons related to air conditioners are based on the technical words, one is BTU and the other is Tonnage.

Be conscious that all the BTU ratings can’t be trusted as they are considered to be high in particular models. Other than BTU you have to give your attention to all other factors.

Presently, Window AC, Inverter AC, Split AC all come with BEE star rating.

Star Ratings

Whenever you are going to purchase an air conditioner, you have to look for the star ratings. These stars are prescribed by the BEE.

Into this formulation procedure, a lot of factors go into it. Here, we will provide charts of star ratings for Window AC and Split AC for 1/12/2016 to 31/12/2017.

Star Ratings of Window AC vs Split AC

Read: Split AC vs Window AC

Below is the defined range of ISEER for Inverter Air Conditioners:

Inverter AC Star Ratings

In these tables, you can see the star ratings with the EER. While you purchase an AC unit, you will see this table as it is a mandatory part of AC manufacturers to include the EER on the star rating sticker.

Also, remember that the 5-star AC is always more expensive than a 4-star AC. Moreover, you will save a lot of energy consumption for an extended period.

Here, we will provide the BEE data of 2018 about the power consumption of several AC units with various ratings and tonnage. This table shows that the higher star rating AC units with lower consumption.

Here, you also can see that the inverter AC units are extremely energy efficient.

No. of Stars 0.75 Ton 1 Ton 1.5 Ton 2 Ton
1 Star Non Inverter 627 843 1246 1648
2 Star Non Inverter 596 800 1184 1626
3 Star Inverter & Non-Inverter 542 747 1104 1448
4 Star Inverter 464 645 945 1293
5 Star Inverter 450 554 840 1113

Read: Inverter AC vs Non Inverter AC

Some Other Important Points to Consider

Apart from the above mentioned technical terms, there are some other points that you have to understand.

Rated Cooling Capacity for a Load of 50%

BEE has made it compulsory for the manufacturers to provide the power consumption at 50% capacity. For example, rated cooling capacity of 50% load of a 1 ton ac will be 0.5 ton.

Rated Cooling Capacity for a Load of 100%

Normal air conditioners have fixed cooling capacity. But, inverter air conditioners works on variable cooling capacity.

According to marketing term, 1 ton AC is equal to 1 ton cooling capacity. But, the tonnage varies from 0.2 ton to 1.2 ton in the inverter air conditioners for its variable cooling capacity.

As per the BEE standards, there you may notice a tolerance of 5% of the tonnage value.

Maximum Cooling Capacity

It means the maximum cooling capacity of an air conditioner. You can see a 1.5 ton inverter AC ranging between 0.3 and 1.8 ton. Here, maximum cooling capacity will be 1.8 ton.

Maximum Power Input

When AC runs at the maximum tonnage, this is the power consumption in watts achieved by the AC.

Rated Power Input for a Load of 50%

This is the power consumption of an air conditioner in watts when it runs at a 50% load.

Rated Power Input for a Load of 100%

This is how much power the ac consumes in watts when it runs at 100% load.

Quick Tips – Before Buying an Air Conditioner

  • Make sure that you have chosen the exact tonnage of an air conditioner as an over sized AC may burn your pockets and may not provide the desired comfort.
  • Also, notice that the EER rating of the AC is given in W/W.
  • Make sure that your air conditioner has the exact star rating labels.
  • While purchasing an air conditioner don’t forget to see the label period section on the label.
  • Keep in mind that more stars ensure more cost and but more savings in future as well.
  • The efficiency of an air conditioner matters a lot as the operating cost also matters more than the capital cost of an air conditioner.

Final Words

If you will use inverter AC, you will notice no big strains on the electricity bills due to the star rating labels that are a welcome attempt by BEE. From the year of 2018, no manufacturer won’t be able to sell non-star rated inverter air conditioners in India.

The biggest misconceptions about the inverter air conditioners regarding the high electricity consumption have been cleared in this article.

So, from now before purchasing an air conditioner ask about all the above discussed jargon then choose the best air conditioner for you.

Overall, it is recommended that you should choose an air conditioner that has a higher rate of all the above mentioned points.


Inverter AC vs Non Inverter AC – Which One is Better?

Split AC vs Window AC – Which One Should You Buy?


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