5-star AC consumes 28 pc more power above 40 deg C: Study

A 5-star rated air conditioner consumes 28 per cent more power when temperature soars above 40 degrees Celsius, a new study said today as it questioned claims by Bureau of Energy Efficiency (BEE) which says a five star AC is supposed to save 22 per cent energy as compared to its one star counterpart.
Centre for Science and Environment (CSE) in its new study claimed that the "5-star" rated split AC becomes "energy- inefficient" as soon as the temperature soars over 40 degrees Celsius and becomes worse than a 2 or 1-star rated AC.
"When the outdoor temperature increases to 40 degrees Celsius, a 5-star rated room air conditioner (RAC) starts performing like a 2-star rated RAC and at above 45 degrees, it is worse than a 1-star RAC.

"A 5-star RAC is supposed to save 20-22 per cent of your energy cost compared to a 1-star RAC, claims the Bureau of Energy Efficiency (BEE). But the CSE study shows in peak summers, when temperatures are in the 40-50 degrees Celsius range, a 5-star RAC can start consuming 10-28 per cent more power than its declared capacity," CSE said.
The study found that with a rise in outdoor temperature, energy performance of RACs drops. Energy efficiency ratio, a measure of energy efficiency of an RAC, drops when the outdoor temperature increases substantially, on an average, 2.5 per cent dip for every degree rise in external ambient temperature above 35 degrees Celsius.

This means a 5-star rated RAC performs worse than a 1-star rated RAC when the external temperature reaches 45 degrees Celsius. At an extreme 50 degrees Celsius, the average energy efficiency ratio was at a level which has been outlawed by the BEE way back in 2010, the study said.

It further added that power consumption increases as outdoor temperature goes up. On an average, power consumption increases by 1.9 per cent for every degree rise in external ambient temperature above 35 degrees.
In peak summers with afternoon external temperatures in the 45-50 degrees range, an RAC unit consumes 10-28 per cent more power compared to its declared power consumption and the consumer incurs more cost to run these ACs during peak times, the study on split RACs said.

CSE said Bureau of Indian Standards (BIS) and BEE must tighten energy efficiency standards and test procedures to reduce margin of deterioration in the real world.
"This is urgent as ACs contribute the most to peak electricity demand in cities and to electricity budgets of households. With extreme weather events, local temperatures are expected to be much higher than the overall city levels - and this will trigger more use of ACs," it said.