Nov 27, 2014

Star Ratings and Air Conditioners: Power Consumption

Arvind M

Ques. Is difference in power consumption between a 2 star AC and a 5 star AC considerable?? Approximately, how much will be the difference per day??

Ans. Star rating is a system initiated by BEE (Bureau of Energy Efficiency) India to determine the energy efficiency of an electronic product for home use like window and split air-conditioners.
Depending on their energy efficiency they are rated on a scale of 1 – 5 and indicated by starts for easy understanding. Higher the number of stars, better is the energy efficiency of an air conditioner.

AC Star rating Calculation

The energy efficiency of an AC depends on two factors: Cooling capacity (in British Thermal Units - BTU) and Power consumption (in Watts)

The cooling capacity of one ton AC should be 12000 BTU, 1.5 ton AC 18000 BTU. Some companies rate their air conditioners as 1 ton but actually their cooling capacity is less than 12000 BTU. SO the BEE has brought into force star rating system so that the manufacturers cannot misguide the consumers

Star rating is based upon the EER of an AC. EER is cooling capacity divided by power consumed. To calculate EER in watts BTU needs to be converted into watts. 12000 BTU is equal to 3517 watts or 1BTU = 0.2937 Watts or one ton = 3517 watts

Inverter ACs

This is a new breed of ACs that consume even less power than a 5 star AC. In an inverter AC the compressor is never shut, its refrigerant flow is slowed down in case the required temperature is reached.

Non inverter or Fixed speed air conditioning deliver a fixed amount of power via a fixed speed. This means the compressor has to stop and start to maintain the desired room temperature. Inverter air conditioning system, varies the speed of the compressors, delivering precise cooling or heating power as required.

The amount of cooling or heating required by an air conditioning unit varies depending on the outdoor temperature and the amount of heat in the room.

When the cooling or heating capacity needs to be increased,the compressor will operate at a high speed and will increase the amount of refrigerant flow. Conversely, during moderate outside temperatures for example, when the cooling and heating capacity needs to be decreased,the compressor will operate at a low speed and will decrease the amount of refrigerant flow. When the inverter air conditioning is switched on, the compressor operates at a high speed in order to cool or heat the room quickly.

As the room temperature approaches the set temperature, the compressor slows down, maintaining a constant temperature and saving energy. Any sudden fluctuation in the room temperature, will be sensed and instantly adjusted to bring the room temperature back to the set temperature. Inverter air conditioning use between 30-50% less electricity to operate.

Let's see what are the benefits of an inverter air conditioner compared with a non inverter air conditioner:-
• At least 30% - 50% cheaper to run as it consumes less power
• Far quicker to achieve desired temperature
• The start up time is reduced by 30%
• Much quieter
• No temperature fluctuations, maximizing comfort level
• No voltage peaks from compressor

All these things aside, the matter of fact is, if you are going to use the air conditioner the whole night every day in the summer season or even the whole day, then buying a 5 star or inverter AC makes sense. If you are buying the AC for occasional use (for example your home is near the coastline) then you can do good with a 2 star AC as the savings of a 5 star would be too little to gauge with occasional use. You need to find a balance between the more amount of money you pay for a 5 star AC  and the money it will save you over the time, typically years.

Also be vary of the fact that ACs today are not so durable, and are very prone to gas leaks. (Gas refills usually cost Rs. 1.5k to 3k). What's the point if in 2 years you save 4000 bucks using a 5 star rated AC and spend 3k getting it fixed in the second year? And do note the fact that 5 star AC's are upto 5k to 10k pricier than their counterparts of lower rating.

Our suggestion to you would be to definitely go for a inverter AC (preferably if you are buying a split) or a 5 star rated AC if you are a heavy user. If the use will be occasional then save your hard earned money and go for a cheaper AC with less stars.

TechTantrik recommends Daikin ACs as they are the most reliable in the market (other brands like LG, Voltas, Samsung, Onida etc. though significantly cheaper are comparatively less reliable). Our recommendation is based on various reviews by people, mechanic/technician interviews and our own experiences with various brand of ACs

You can calculate the difference between the power consumptions and savings from this online calculator by Daikin


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  4. Hi, nice article. And most importantly useful. I'm thinking about replacing their air conditioning, and very handy that stumbled on your article. These two factors are very important, I choose myself conditioner based on your calculation. I've already called masters for installation on Monday, please correct the link with the calculator, it does not work, but very necessary. I would be very grateful to you.

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  6. Hello, nice post. These two factors are very essential. Higher the number of stars, better is the energy efficiency of an air conditioner. We also aware of that. Thanks for the nice post.

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