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Explained: Why you should keep the AC at 24°C

From an electricity bill savings point of view, changing the temperature setting to 24 degrees from the current 18 degrees will reduce the power bills by around Rs 4,000.

December 10, 2019 / 11:02 AM IST

A move by the power ministry to increase the default temperature in air conditioners to 24 degree celsius will help you save almost Rs 4,000 on annual electricity bills, apart from reducing energy consumption.

The Ministry of Power (Bureau of Energy Efficiency) has said that all room air conditioners (AC) will have to ensure a default temperature setting of temperature in the appliances at 24 degree celsius from January 1, 2020.

This will mean that a new AC will have 24 degrees as the pre-set temperature when the appliance is switched on. Individuals desiring a lower temperature can reduce it manually.

While the power ministry has taken a decision to have a set temperature, there is a deeper reason behind this move.

Why is the temperature set at 24°C?

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The Bureau of Energy Efficiency (a body of the Ministry of Power) has said that the reduction in AC temperatures to 24 degrees from the conventional 18-21 degrees can result in 24 percent of energy savings.

Countries like Japan and the US have already put in regulations for the functioning of air conditioners. Japan introduced a default setting for air conditioners at 28 degrees celsius. In the United States, some places have enforced limits on lowering the air condition beyond 26 degrees celsius.

How much energy can be conserved?

The overall potential for energy conservation through such measures is estimated to the tune of 20 billion units (worth Rs 10,000 crore) annually. If about half (50 percent) the consumers adopt to such recommendations, this would result in about 10 billion units of electricity, which is equivalent to the reduction of 8.2 Million tonne of carbon dioxide per year.

From an electricity bill savings point of view, changing the temperature setting to 24 degrees from the current 18 degrees will reduce the power bills by around Rs 4,000 annually. Increasing the temperature further to 27 degrees will reduce the yearly bill by almost Rs 6,500 compared to 18 degrees.

Would it be feasible to have the AC temperature at 24 degrees in a humid weather?

The Normal human body temperature is 36-37 degree celsius. Hence, to take a temperature closer to 24 degrees is considered to be healthier for individuals in tropical regions like India. The ministry says that, as per the comfort chart, temperatures up to 25 degrees are quite comfortable for human body, along with the desired humidity and air movement values.

According to ASHRAE Standard 55-2013 Thermal Environmental Conditions for Human Occupancy, The thermal comfort zone is the condition of mind which expresses satisfaction with the thermal environment. This condition is defined using temperature, humidity level and air flow experienced by the human body, apart from individual parameters such as clothing and metabolism. Technical analysis indicates that, in order to achieve the desired comfort level at a steady state, the temperature setting can be 24-25 degree celsius.

Wouldn’t it take more time to cool a room?

This is a common misconception. The thermostat in the AC just checks the temperature of the air inside the room and stops the compressor when the temperature reaches the desired level.

This means that the compressor will work longer if the temperature is set to a lower level. So, it will work more and use more electricity if the temperature is set to 18 degree celsius than if it is set to 24-degree celsius. This is because it will take less time for air to reach 24-degree celsius than 18 degree celsius as the compressor is working with the same power or wattage.

Why is India taking this step?

The Bureau of Energy Efficiency estimates that, considering the current market trend, the total connected load in India due to air conditioning will be about 200 GW by 2030. This may further increase as only 6 percent of households are using one or more air conditioners at present.

If the measures are followed by all consumers, India can save about 23 billion units of electricity. The total installed capacity of air conditioner is about 80 million TR (tons of refrigeration or amount of cooling required to convert 1000 Kg of water into one tonne of ice in 24 hours), which will increase to about 250 million TR in 2030.

The demand for room ACs in India is expected to touch one billion units by 2050, compared to 6.5 million units right now. On the other hand, ACs account for 10 percent of the global energy consumption.
M Saraswathy
first published: Dec 10, 2019 07:54 am
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