Your ‘5-star’ rated split AC becomes energy-inefficient as soon as the temperature outside rises above 40 degrees C. In fact, it becomes worse than a 2- or even 1-star rated AC. These are the findings of a new study done by Centre for Science and Environment (CSE), the report of which was released on July 28.
The CSE released the results of its lab tests of energy performance of popular 5-star rated split room air conditioners (RACs) under normal and maximum temperature conditions. The tests were carried out in a National Accreditation Board for Testing and Calibration Laboratory (NABL), a Delhi-based accredited laboratory.
As per the Bureau of Energy Efficiency, a 5-star room AC is supposed to save 20-22 % of your energy cost compared to a 1-room AC. The CSE study shows in peak summers, when temperatures are in the 40-50 degree C range, a 5-star RAC can start consuming 10-28 % more power than its declared capacity. Further, its cooling capacity also drops by about 30 % in peak summers, which means a 1.5-tonne AC acts like a 1-tonne AC. And if you lower the room temperature artificially to below 27 degrees the energy efficiency dips further.
“The Bureau of Indian Standards (BIS) and BEE must tighten energy efficiency standards and test procedures to reduce margin of deterioration in the real world,” says Anumita Roychowdhury, executive director-research and advocacy, CSE.
“This is urgent as ACs contribute the most to peak electricity demand in cities and to electricity budgets of households. With extreme weather events, heat waves and heat island effects becoming common, local temperatures are expected to be much higher than the overall city levels – and this will trigger more use of ACs,” she adds.
In Delhi, air conditioning accounts for about 28 % of the total monthly electricity consumption during the hottest months. And according to the BEE, ACs are responsible for almost 60 % of the Delhi’s peak electricity demand.
As per the CSE researchers, only split RACs were selected for the study because as per the Indian Society of Heating, Refrigerating and Air Conditioning Engineers (ISHRAE), the split RAC segment has seen the maximum market growth in India. Currently, split ACs corner 61 per cent of the RAC market. The researchers emphasise that the study is not a ranking of companies or their products, but to get indicative results, it has selected some popular models that represent a sizeable market share.
Implications of the findings
“While some deterioration in energy performance and cooling capacity is expected under climatic stress during hot summer months, such short duration spikes can undermine long term energy savings and monetary gains,” says Roychowdhury.
In monetary terms, running a 5-star RAC for a couple of hours in afternoon during summers under normal conditions should cost about Rs 490 a month. But with worsening of its energy performance, it can cost anywhere between Rs 660-780 (based on Delhi’s non-subsidised tariff rate of Rs 5.8 per unit). It will also cool about 30% less.
With climate change, more extreme weather conditions and heat waves, this has serious implications. The observed temperature data for 60 cities in different climatic zones available from the BIS shows that 41 cities have at least 175 hours in a year when external ambient temperature is above 35 degree C. Out of these 41cities, 22 including, Delhi-NCR, Jaipur, Ahmedabad, Lucknow and Raipur experience temperatures around 40 degree C or above.
This is worsened by the heat island effects that increase local temperature conditions by almost another 8-10 degree C than the ambient air temperature. A study by the Indian Institute of Technology, Delhi shows that average ambient temperature in Delhi during April, May and June is about 38 degree C, but in the micro-climate of Connaught Place in the centre of the city, it can be 46-48 degree C. Also RACs themselves contribute to the heat island by warming up the immediate environment outside.
“While this study is limited to split RACs, a similar assessment will have to be done for inverter ACs and window ACs. At the next level of review of the star labelling programme, it is important to make the labelling programme technology-neutral and develop more stringent test procedures and systems for monitoring of real world performance,” she adds.
The way ahead
CSE recommends the following steps to meet targeted real world energy efficiency performance:
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. The star labelling system should be adapted to this system.
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.