Most of the air conditioner consumers have no clue about what are the different AC standards and ratings. Even if they have heard those jargons, actual meaning is still not clear to them.
That is not all, even AC manufacturers market their product with different technical jargon. Just to adding more confusion. Or is that intended marketing gimmick? There is a famous saying:
If you cannot convince anyone, ensure that you confuse them
Majority of the people have no understanding of marketing details and technical definition of the manufacturer. This is unfortunately a true fact. Just check this by yourself. Do you know what are these ratings?
Tonnage / BTU
BEE (Bureau of Energy Efficiency)
ISEER Star Ratings
So with that background, we are trying to define those jargons for the general consumers. Hopefully this will help at least few air conditioner buyers. At the minimum, you will be able to ask some questions to the seller after reading this post.
Capacity – What is AC Tonnage?
First question the sales person asks you is what capacity of AC you looking for? Do you want 1.5-ton AC or a 1-ton AC?
What do they mean by “ton”? Definitely not the tons of weight 🙂
So in the air conditioner jargon, ‘ton’ refers to the amount of heat removed by the air conditioner in one hour. Higher the value of ton, higher the cooling capacity.
What is BTU of an air conditioner?
In India, you use the British system for measuring a lot of things. Wiki page has the full definition of BTU.
BTU is the “amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit.” In simpler terms, we can say that 3,412 BTU = 1 Kw/hr
In simple terms, a ton is the amount of space cooled by 1 ton (weight) of ice. Therefore we can say that:
1 ton = 12,000 BTU/hr
Meaning of 1.5 ton, 2 ton, 3 ton air conditioner
Air conditioners specification includes different tonnage such as 1-ton, 1.5-ton, 2-ton, and so on. What does it indicate?
The tonnage is the amount of heat the air conditioner removes from the room in one hour. The mathematical unit for tonnage is BTU (British Thermal Units). 1 ton equals 12000 BTU. Higher the BTU, the greater is the cooling effect.
Tonnage or size of AC depends 4 different factors as indicated above. Additionally, depending on number of family members, you can decide on the size of AC needed for your needs.
Rule of thumb – tons of AC per square foot
Though the capacity needed varies per individual needs, there is a common rule of thumb.
It’s often in the neighborhood of 1 ton of air conditioning capacity for each 600 square feet of conditioned floor area, usually abbreviated 600 sf/ton
Rated cooling capacity of an AC
Rated cooling capacity of an AC is defined in terms of ‘a ton’. One ton is equal to 12000 BTU per hour.
For example, a 2-ton AC will remove 24000 BTU of heat per hour from the room. The requirement for the room can vary depending on various factors discussed earlier. It is advisable not to oversize the AC because it can affect the performance of the AC.
All AC manufacturers are mandatorily have to include rated power input figure. This is visible on the star rating label.
Rated power input is equivalent to the power consumption in Watts when the AC runs at 100% load.
For example, 1.5-ton AC will consume about 1500 w/hr. Hence, you can see that the AC will consume around 1.5 to 2 units per hour.
But there is a catch. If you use the AC continuously for say 5 hours, then consumption is not 2 times 5. As the compressor switches off and on at regular intervals, the consumption of 5 hours will definitely be less.
Efficiency – What are the Different AC Standards?
Lets check the definition of these different efficiency ratings and also star rating of the air conditioner.
EER – Energy Efficiency Ratio
The EER is a very important ratio that differentiates between AC units. Scientifically, EER = Amount of heat removed per hour divided by the amount of power consumed.
Therefore the formula is: EER = BTU/hr/Watt
The higher the EER, the better is the performance because the air conditioner removes more heat per hour per unit of power consumed. Thus, you can deduce that an air conditioner with a higher EER is more efficient.
CoP – Co-efficient of Performance
You need to do some simple mathematical calculations to arrive at the CoP. In order to understand the concept of CoP, you should know the relation between BTU and KW hr.
1 KW hr = 3412 BTU. Alternatively, you can say that 1 KW = 3412 BTU/hr.
Therefore the formula is: 1 W = 3.412 BTU/hr
Now, CoP is the amount of heat removed by the air conditioner in Watts divided by the power consumption in Watts. Hence, CoP does not have any units. Higher the CoP, higher is the efficiency of the air conditioner unit. Let us now look at the relation between EER and CoP.
Relation between EER and CoP is defined as: EER = 3.412 X CoP
Star rating is most visible and is in bright colors on every air conditioner appliance. So, what are they? The Bureau of Energy Efficiency, Department of Energy Savings Government of India prescribes these star ratings for various electronic products. A lot of factors go into the formulation process.
These star ratings are fixed for specific periods. So, they keep evolving.
You should look at the star ratings along with the EER. It is mandatory on the part of AC manufacturers to include the EER on the star rating sticker.
ISEER – Indian Seasonal Energy Efficiency Ratio
Before knowing ISEER, you need to understand what is Seasonal Energy Efficiency Ratio (SEER).
If the temperature outside the house is more, the AC consumes more electricity to cool the interiors. The temperatures in the rainy season and winters are much less than what you get in the summer season. Therefore, the EER of the AC varies depending on the season in which you use the appliance. This is the concept of SEER.
Lets now come to ISEER. Concept of ISSER is similar to that of SEER. Difference is that ISEER considers couple of additional factors.
- Cooling Seasonal Energy Consumption (CSEC): Total energy consumed by the AC when it is in active mode
- Cooling Seasonal Total Load (CSTL): Total heal removed by the AC in active mode.
Thus, ISEER = CSTL/CSEC (ratio of total heat removed to total energy consumed)
The BEE makes it mandatory for Indian AC manufacturers to declare the ISEER on the star rating label.
As you have seen above, there are many ratings that an AC appliance will be rated with. So you should be aware of certain terms and concepts while buying your best AC unit. Therefore take good care that you understand these various terms and ask right question to your dealer or shopkeeper.
If you read and understand these jargons, no dealer or manufacturer will be able to confuse you with jargon. We wish this post can equip you with the knowledge to question the manufacturer or the dealer to ensure you get the best deal.