5-star ACs fail to save energy as mercury rises, says CSE study

  • HT Correspondent, Hindustan Times, New Delhi
  • Updated: Jul 27, 2016 23:15 IST
A Centre for Science and Environment study has said an AC’s energy efficiency becomes worse as the mercury rises.

If you thought your 5-star split AC becomes energy-efficient as soon as the temperature soars over 40 degrees, it is time to think again.

A study has said an AC’s energy efficiency becomes worse as the mercury rises. When the outdoor temperature increases to 40 degrees, a 5-star rated room air conditioner (RAC) starts performing like a 2-star AC. Above 45 degrees, it is worse than a 1-star AC.

“At an extreme 50 degrees, the average energy efficiency ratio was at a level that was outlawed by the Bureau of Energy Efficiency (BEE) way back in 2010. A 5-star AC is supposed to save 20-22% of your energy cost compared to a 1-star AC,” said Anumita Roychowdhury, executive director-research and advocacy, Centre for Science and Environment (CSE), while releasing the study on air conditioners on Wednesday.

“Our study shows that in peak summers, when temperatures are in the 40-50 degrees celsius range, a 5-star AC can start consuming 10-28% more power than its declared capacity. This adds to the peak load demand on the electricity grid,” she said.

According to Roychowdhury, CSE wanted to find out how room AC units perform under different outdoor temperature conditions and how that affects the energy saving from the star labeling programme of the Bureau of Energy Efficiency (BEE).

The tests, which measured energy performance of popular 5-star split room ACs under normal and maximum temperature conditions, were carried out in a National Accreditation Board for Testing and Calibration Laboratory-accredited facility based in Delhi.

In the Capital, air conditioning accounts for about 28% of the total monthly electricity consumption during the hottest months. According to the Bureau of Energy Efficiency, ACs are responsible for almost 60% of Delhi’s peak electricity demand.

Read: Delhi roads get safer as congestion grows: Study

The study said the cooling capacity of room ACs drops by about 30% during the peak of summer, which means a 1.5-tonne AC acts like a 1-tonne AC.

“On an average, the cooling capacity drops by 1.4% for every degree increase in the external ambient temperature above 35 degrees. Overall, an 8-21% drop has been measured at 40-50 degrees from the declared cooling capacity of the models,” the study says.

Its said lowering room temperature more than it is required leads to drop in energy efficiency. According to the National Building Code, thermal comfort lies between temperature values of 25 and 30 degrees, with the optimum condition at 27.5 degrees. However, people lower room temperatures to as low as 20 degrees. This leads to enormous energy penalty.

“The energy efficiency was measured at 15.31% when the room temperature was lowered from 27 to 20 degrees. This works out to a 2.19% drop in energy efficiency ratio for every degree of lowering of internal temperature below the standard 27 degrees,” Roychowdhury said.

What can be done?

CSE recommendations

BIS should amend Rule (IS 1391 part 2) to incorporate an additional test for testing of energy efficiency ratio based on multiple higher temperature range relevant for different climatic zones for testing and rating of ACs

BEE should make it mandatory for manufacturers to declare the tests results carried out based on multiple higher temperature range and declare the results on their product labels

Manufacturers should declare the annual energy consumption based on cooling capacity tests

Ratchet the existing star rating to get the best technology in the Indian market

Actively promote passive architectural features to reduce thermal load of buildings

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