Efficient air-conditioners may well be a misnomer, according to a recent study by the Centre for Science and Environment (CSE). An AC with energy ratings of 5-stars performs like one with 2-stars when the temperature soars to 40ºC, said the study.

The performance further dips to a 1-star level by the time the mercury touches 45ºC, CSE’s lab results showed.

“In peak summers, when temperatures are in the 40-50ºC range, a 5-star room AC can start consuming 10-28 per cent more power than its declared capacity, thus adding to the peak load demand on the electricity grid,” noted the study, which tested ACs under normal as well as extremely high temperatures.

CSE conducted the tests on three ‘popular’ split AC models from Voltas, LG and Godrej, and all the three failed the tests at higher temperatures.

While Voltas and LG ACs performed optimally at 35ºC, the Godrej AC’s energy efficiency ratio (EER) dropped to 4-star levels.

The LG AC performed better than the other two at 40ºC and 45ºC at 3-star and 1-star level, respectively, against 2-star and 0-star for the other two companies. At 50ºC all the three dropped to 0 star levels, according to the study.

It is estimated that ACs account for as much as 28 per cent of the total monthly electricity consumption in Delhi. The think-tank estimates room ACs might be consuming about 96 billion units of electricity if they function at their declared ratings.

“On an average, there is a 2.5 per cent dip (in efficiency) for every degree rise in external ambient temperature above 35ºC. This means a 5-star rated room AC performs worse than a 1-star rated room AC when the external temperature reaches 45ºC. At an extreme 50ºC, the average EER was at a level which has been outlawed by the BEE (Bureau of Energy Efficiency) way back in 2010,” said the study. Naturally, the study finds a resultant increase in power consumption at an average rate of 1.9 per cent for every degree rise in external temperature above 35ºC.

The test results were in line with earlier findings of the BEE, which had published names of the companies whose models failed its random sampling in 2014 and 2015. Some of the companies that failed the compliance tests were Samsung, Godrej, Panasonic, O General, Whirlpool, IFB and Videocon.

Countering findings CSE explained that these companies had countered the BEE’s findings with claims that the named models were discontinued before the results came out.

“It has been noted that companies periodically change the model names by modifying any minor feature, thus escaping BEE scrutiny,” CSE said.

When asked about the study, Vijay Babu, Business Head-RAC, LG Electronics India, said: “All electronic goods from reputed companies are developed and tested as per the standards set up by relevant authorities. Air conditioners too follow the IS-1391 (part 2) laid down by Bureau of Indian Standards and energy efficiency norms laid down by BEE.

“The study by CSE states that there is reduction in energy efficiency at higher temperatures, which is due to the very nature of the product and is not specific to any particular brand of AC.

“The same is also mentioned in the study which says, ‘CSE researchers point out that it is not unusual for RACs (rooms ACs) to consume more power to cool and suffer energy efficiency loss under climatic stress.’