Energy Consumption and Star Rating for an Appliance

The air-conditioners are big energy guzzlers. Energy star rating is expected to help improve the energy efficiency of these air-conditioners. How does a consumer evaluate the benefit of higher energy star rating?

 

 

Let us take a simplified example. Let us do calculation for a 2 Ton AC. 2 Ton is nominal output. Every model or brand may have a different exact output (all of them would be near 2 Ton). Let us consider 7 kW output. For a given output, the input power required would get defined as Input Power = Output Power / EER, where EER is Energy Efficiency Ratio. Thus higher the EER, lower is the input energy required for a same capacity of the output. Also higher the EER, higher is the energy rating.

The energy start ratings also keep on changing. The BEE published energy star rating for Jan 2014 to Dec 2015 are:

Jan 2014 to Dec 2015

Energy Star

Min EER

Max EER

1

2.7

2.89

2

2.9

3.09

3

3.1

3.29

4

3.3

3.49

5

3.5

 

 

So let us consider two AC pf 2 Ton (7kW output) with EER or 2.9 (2 star) and 3.3 (4 star). So how much electricity can be saved in a year.

For the same output of 7kW, the 4 star would consume 2.121 kW (7 divided by 3.3) and 2 star would consume 2.414 kW. Let us consider that an AC compressor operates on an average 10 hours in a day for 6 months in a year. Thus the energy saving by a 4 star AC would be 0.293 kW*10*6*30 and would be equal to 527.4 units. For a peak rate of Rs 7.25/unit for a place like Gurgaon, this means saving of Rs 3824. This gives you a basis of selecting whether to buy a 2 star AC or 4 star AC.

 

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