Excessive use of air conditioners might lead to more power outages in coming days

With the Electricity board blaming the surge in power demand due to increase in usage of air conditioning (AC) units for the power outage last week, more such breakdowns could be expected, considering the dog days ahead. 

In the desire to stay cool in summer, how does one ensure that power bills do not go through the roof? To understand the billing, one should understand what AC tonnage means and how much power is consumed, when an AC is used for one hour. 

According to experts in the field of air-conditioning, an AC’s cooling capacity depends on the area of the room, number of windows, sunlight, heat producing appliances in the room like computer and light and metal objects which absorb heat. Most homes, depending on ceiling heights, windows, and airflow, will need a ton of air conditioning for every 400 to 1,000 square feet. “Higher air conditioning tonnage can mean higher energy costs, because the more tonnage an air conditioner is rated for, the more work it is forced to do. It is always wise to get an energy- rated AC which will lead to cost saving,” said KM Palani, who runs an AC servicing and repair unit in Kolathur. ACs used in the city account for nearly 3,000 MW peak power during summer, according to Tamil Nadu Generation and Distribution Company (TANGEDCO) officials. Peak power demand last year crossed 15,000 MW (15,343 MW) on April 29, whereas demand averages slightly more than 13, 500 MW as of May 3. 

On cutting down power charges, a household with a bimonthly power bill of around Rs 600 will spend slightly more than Rs 2,000 when a 1 ton AC is used at night. But most people use the ploy of switching off ACs early in the morning and switching on fans. “A one ton AC would consume 2 units per hour, 1.5 ton AC 3 units per hour and a 2 ton AC 4 units per hour,” a TANGEDCO official said. 

“With almost every middleclass home owning at least one to two AC units, the power consumption multiplies even if the units are operated for a minimum of four hours every night. This is the main cause of worry during summer months,” the official added. 

Although usually three-star rated ACs are enough for houses, a higher star rating is meant for offices with a constant flow of people in and out of AC rooms, officials add. But another official said higher star rated ACs could also be used for houses, as its lower wattage would ensure lower power dues.  

Asked about AC’s with inverters which is now a new trend, an official said such ACs would save nearly 40% power in addition to continuing to function during sudden power outages. But another said that opting for ACs with five-star rating would lower consumption charges due to its low wattage. 

Besides, improperly maintained cooling towers for ACs can promote microorganisms like Legionella pneumophila, responsible for Legionnaires disease. Conversely, air conditioning (including filtration, humidification, cooling and disinfection) can ensure a clean and safe, atmosphere in hospital operation theatres and environments where proper atmosphere is critical to patient safety. “But excessive AC use can negatively affect the skin causing it to dry and lead to dehydration,” Palani said. “Another way to keep a house cool without resorting to ACs, is to keep the windows and blinds around the house closed; especially those facing the west and southwest directions should be closed. It’s also good to plant enough trees around the  house to ensure the home stays cool during the hottest part of the day, besides putting up light coloured (white or cream) curtains and blinds,” said Poonam Jhaver, founder, director of Elan, a city-based furniture boutique.

Air conditioning is the process of removing heat from a confined space thereby cooling the air, and removing humidity. ACs are also used to cool/ dehumidify rooms containing heat-producing electronic devices like computer servers and power amplifiers. 

ACs are defined in tons. Numerous brands offer domestic ACs in 1, 1.5 and 2 tons. Tonnage here does not define weight. HVAC (Heating, Ventilation and Air Conditioning) professionals reveal that one ton refers to the heat an AC can remove in one hour which for a 1 ton unit is approximately 12, 000 BTU (British Thermal units). A BTU is roughly the heat from burning a kitchen match all through. 

Before Willis Carrier  invented ACs, buildings were cooled in summer with ice harvested from rivers and lakes in winter. Strangely enough, the BTU formula refers to ice production during winter on the Hudson River in the  US and the heat needed to  melt one ton ice in 24 hours.