In the world of electronic appliances, there is a lot of jargon!
You must have heard your Air Conditioner repairman using terms which you didn’t understand! There is a majority of people who cannot make sense of what the manufacturer is trying to convey. People end up being confused.
Let us take the example of ‘Star Ratings’. People only know that the ‘Energy Star’ or ‘Star Label’ is a government-backed symbol. And a higher star rating is better than a lower star rating.
With this limited knowledge, people move to buy an electronic appliance such as an A.C.
You can read our reviews & buying guide on Best Air Conditioners.
In this article, we’ll bring to light the various factors which control the star ratings so that next time you go to the AC shop with some knowledge about the system.
Let us now understand some of the important tidbits or terms used by the AC manufacturers.
When we say that we have a 1-ton or a 1.5-ton air conditioner in our home, does it mean that we are talking about its weight? Definitely No!
Air conditioning has nothing to do with the weight.
Here ‘ton’ implies the amount of heat removed by the AC in one hour.
How Do We Measure the Amount of Heat Removed?
We measure the amount of heat removed in terms of BTU (British Thermal Units). Higher the amount of heat removed, higher will be the BTU. And a higher BTU means greater cooling capacity.
Definition of BTU
Earlier, one ‘ton’ was referred to as a space that ‘1-ton’ of ice can cool.
BTU is defined as the amount of heat required to increase the temperature of one pound of water by 1degree Fahrenheit.
Or we can say, 3,412 BTU = IKW/hr.
I ton = 12,000BTU/hr.
2 ton = 24,000BTU/hr and so on.
How to Choose the Right Tonnage AC?
Now that we know what does the term ‘ton’ means in an AC, next question is, what size or tonnage of the AC should be chosen.
It is a burning question!
It depends upon several factors like:
- Size of the room
- Number of people in the room
- Number of appliances in the room
- City where you live
Please note that it is important to choose the right size of an AC.
An undersized AC cannot cool properly, whereas an oversized AC consumes more electricity.
If a room needs 1.2 tons of cooling, it is not a wise choice to buy a 5 star 1.5 ton AC. Instead, you can buy a 3 star 1.2 ton AC.
After the size of an AC, comes efficiency.
It is a major factor which tells how useful a machine is.
According to Layman, “Efficiency is output divided by input”.
It indicates how well the input energy is converted into useful output energy or work.
While we discuss how efficient an AC is, we need to look into the following aspects:
Energy Efficiency Ratio or EER
EER is defined as the heat removed per hour divided by the total power consumed by the AC.
Simply, Efficiency = heat removed per hour / power consumed
Or, EER = BTU/hr/watt.
Higher the amount of heat removed, more efficient is the AC.
Also, higher is the EER; better is the air.
Usually, EER of an AC is measured under the specific conditions:
- 35 degrees Celcius outdoor temperature.
- 27 degrees Celcius indoor temperature.
- 50% Relative Humidity.
Co-efficient of Performance or COP
Let us first understand how BTU and KW/hr is related to each other.
We already know that 1 KW = 3412 BTU/hr or 1 watt = 3.142 BTU/hr.
COP = amount of heat removed per watt / power consumed in watts.
So, COP is a unitless quantity. It is a ratio of the amount of heat removed per watt to the amount of power consumed in watts.
EER = 3.142 COP.
A high EER means a high COP. Higher the value of COP, better is the AC.
BEE Label or Energy Star
Whenever you go to buy an electronic appliance like an AC, you will find a sticker on the same. BEE (Bureau of Energy Efficiencies) makes it mandatory for every Air Conditioner to have a star label on it.
The star ratings of an AC depends upon EER and COP. Energy star starts from 1-5.
In India, the star ratings are revised from time to time. You can find the validity of the label from the ‘label period’ section printed on the label.
SEER (Seasonal Energy Efficiency Ratio)
SEER takes into account internal as well as external temperature. We know that the temperature does not remain the same throughout the year. The temperature is low in winters, so is the usage of an AC.
So, SEER measures how well an AC performs during seasonal changes.
Higher the SEER, more efficient is the AC.
ISEER (Indian Seasonal Energy Efficiency Ratio)
When we talk about SEER, we need to consider that seasons differ from country to country.
So, there is a different SEER ratio for different countries.
Clearly, in India, we have Indian Seasonal Efficiency Ratio.
The concept of EER and ISEER is same. The only difference is that ISEER considers the seasonal factors also.
ISEER = CSEC/CSTL or heat removed/energy consumed.
It stands for Cooling Seasonal Energy Consumption.
It represents the total amount of energy consumed by an AC when it is in active mode.
CSTL or Cooling Seasonal Total Load is the amount of heat removed by an AC while in active mode.
BEE Star Ratings for Window ACs 2017 vs 2018
We have discussed that the star ratings keep changing for different air conditioners from time to time.
So, it is necessary to know about the label period of the AC before you buy it.
In this section of the article, we have gathered EER and ISEER data for ACs.
Let us start with the EER star ratings of window AC for 2016-2017.
BEE Energy Efficiency Ratings (EER) for Window AC
From 1st Jan 2016 to 31st Dec 2017
BEE proposed that star ratings for the window AC should be improved during the label period 2018 to 2019.
Proposed Star Rating plan for Window ACs
Validity: 1st Jan 2018 - 31st Dec 2019
But, this proposal was rejected. Manufacturers found it impractical to focus on improving the star ratings of window AC because the market share of window AC is declining every year.
Keeping in view all the points made by the manufacturers, BEE revised the data and finalised the following star rating for window AC during 2018-2019:
Star Rating Table for Window AC
Validity: 1st January 2018 - 31st December 2019
It is clear from all this data that the star ratings for a window AC have not been updated for a long time. The only change is that the EER ratio has been replaced with ISEER ratio.
BEE Star Ratings for Inverter ACs
Let us now talk about the Inverter ACs and see how does the star ratings impact these ACs.
An Inverter AC was introduced a couple of years ago in the Indian Market. These ACs hold a record of good performance in the International Market. But, in India, these AC units are still in a nascent stage.
An Inverter AC didn’t have a star rating system when they were introduced in the market.
As of now, it is compulsory for the manufacturers to declare the ISEER ratio on the Inverter ACs.
Let us start with the EER star ratings for Inverter AC from 2016-2017.
Star Ratings for Inverter ACs
From 1st January 2016 to 31st December 2017
The defined ranges of the ISEER for 2018-2019 are as under:
Star Rating Level for Inverter ACs
From 1st January 2018 to 31st December 2019
If we compare these two tables with those included earlier in the article, we find a difference. The efficiency and the star ratings are higher than the previous years.
‘A 5-star AC in 2017 with EER 3.50 has become a 3-star AC in 2018.’
What Does This Change Entail?
Everything comes with a cost. No doubt, an Inverter AC is more efficient than a fixed-speed AC. At the same time, it is more expensive as well.
It again brings you to confusion as to whether you should buy this or not!
Based on the 2017 BEE data, we have taken the annual power consumed in kW/hr for an average of 1600 hours:
Power Consumption Table
It is evident from this table that a 3-star inverter AC is more efficient than a 5-star non-inverter AC.
If we consider the amount of one unit of electricity to be around Rs.6, our savings for a 5-star inverter AC over a 5-star non-inverter AC (both of 1 ton), will be Rs. 1218. It will save 203 units of electricity!
The inverter AC units are costlier than a non-inverter AC unit.
So, it is up to the person to choose the right type of AC which meets his/her requirements.
Some Useful Tips to Share
Now that we have discussed the various terms related to air conditioners, we are going to share some useful tips related to the article:
- Always choose the right tonnage of the ACs. If your room needs a 1-ton AC, buying a larger AC is not a good choice. Similarly, if you buy an undersized AC, it will end up with a poor performance.
- The star ratings are provided for a range of EER. It means that a rating of 3.49 or 3.50 does not make a huge difference in efficiency. However, a change is rating from star-3 to star-4 increases the cost of an AC. So, you should check the EER ratio as well.
- The EER on the labels is given in watts/watts. You may also find EER in BTU/hr/watt. Don’t get confused between the two as we have already explained the units in detail.
- It is true that ‘More Stars – More Cost’. But, ‘Watt is a tip!’ A 5-star AC is costlier than a 1-star AC of the same company. An inverter AC costs even more. We also know a 5-star AC is more efficient than a 1-star AC. It means that a 5-star AC will provide the same cooling using lesser electricity. It means that you can make savings in the operation cost. You can recover the capital cost used to buy a higher star rated AC in a matter of a few years. So, we can say ‘More Stars – More Savings’.
- Please note that the star rating levels change every two years. We have included tables in our article which will give you an idea about the validity of the present rating period. Ensure that the new air conditioners have the revised star ratings.
Apart from these tips, the efficiency of an AC also depends upon how you use it. The frequency of usage is also an important factor in the efficiency.
We have shared the various important factors to take into account before you invest in an Air Conditioner.
Now you have good knowledge to question the dealer or the manufacturer to avail the best deal.
We are sure that no dealer will be able to confuse you with the complex jargon. The dealer might end up being confused by your questions, instead!