What an air conditioner actually costs to run in India

The formula, and why the sticker does not tell you

Electricity is billed in units, and one unit is one kilowatt drawn for one hour. So the cost of running anything is power in kilowatts, multiplied by hours, multiplied by the per unit tariff. The complication with an air conditioner is that it does not draw its rated power continuously. It works hard to pull the room down to your set temperature, then works much less to hold it there.

That is the whole case for an inverter compressor. A fixed speed unit can only switch fully on or fully off, so it overshoots and restarts repeatedly. An inverter throttles down and holds, which is where the saving comes from.

Take the middle of each range and the difference is around four units a day, or about ₹32 at ₹8 a unit. Across a 150 day season that is roughly ₹4,800. The price gap between a decent three star and a decent five star inverter is usually ₹8,000 to ₹12,000, so the payback lands at around two seasons, and everything after that is yours.

What actually moves the number

• The set temperature. Each degree lower costs meaningfully more, because the compressor has to run longer to reach and hold it. The Bureau of Energy Efficiency's default recommendation of 24 degrees exists for this reason, and the difference between 20 and 24 is large.
• Hours, more than anything else. Halving runtime halves the bill, and no efficiency rating will ever beat simply not running it.
• Sealing the room. An open door or an unsealed window means you are cooling the corridor. This is free to fix and it is the highest return change most people can make.
• Servicing. A clogged filter or a dirty coil makes the compressor work longer for the same result. An annual clean is cheap.
• Sunlight. Curtains on a west facing window cut the heat the unit has to remove in the first place.

Should you replace a working unit?

Usually not. The payback arithmetic above compares two new units at the point of purchase, which is a genuine choice. Scrapping a functioning three star to buy a five star is a different question, because you are now paying the whole price of the new machine rather than the gap, and the payback stretches well past five years. Buy the efficient one when you are buying anyway.