For many Indian homes the air conditioner is the single biggest reason the summer electricity bill jumps. The good news is that you can work out its cost in advance with one simple formula, and a few habits make a large difference.
The Formula: Watts to Units
Your electricity bill counts energy in units, and one unit is one kilowatt-hour (kWh): 1,000 watts used for one hour.
Units = Power (watts) × Hours used ÷ 1,000
Multiply by the number of days to get a monthly figure, then by your tariff to get the cost. The same formula works for every appliance in the house.
A 1.5 Ton AC: Two Examples
Assume the AC runs 8 hours a night for 30 days, and electricity costs ₹8 per unit.
- Older non-inverter AC drawing about 1,500 watts: 1,500 × 8 ÷ 1,000 = 12 units a day, or 360 units a month. At ₹8 a unit, that is about ₹2,880 a month.
- Inverter AC averaging about 900 watts: an inverter compressor slows down once the room is cool instead of switching fully on and off. At an average of 900 watts, it uses 216 units a month, about ₹1,728, saving roughly ₹1,150 a month, or over ₹4,600 across a four-month summer.
Real consumption depends on the outside temperature, the room size, insulation, the set temperature and how often the door is opened, so treat these as typical figures rather than exact ones.
Use the Star Label for a Better Estimate
The BEE star label on an AC shows its estimated energy use in units per year. That figure is based on 1,600 hours of use a year. Divide by 1,600 to get the units per hour. For example, if the label says 1,000 units a year, the AC uses about 0.625 units an hour, so 8 hours a day for 30 days is about 150 units, or ₹1,200 at ₹8 a unit. Comparing this figure between models is the quickest way to see which one will cost less to run.
How the AC Compares With Other Appliances
| Appliance | Typical use | Units a month | Cost at ₹8/unit |
|---|
| 1.5 ton AC (non-inverter, 1,500 W) | 8 hours a day | 360 | ₹2,880 |
| 1.5 ton AC (inverter, about 900 W) | 8 hours a day | 216 | ₹1,728 |
| Ceiling fan (75 W) | 10 hours a day | 22.5 | ₹180 |
| LED bulb (9 W) | 6 hours a day | 1.6 | ₹13 |
One AC can use as much electricity as 10 to 16 ceiling fans running all day, which is why the AC deserves the most attention when you try to cut the bill.
Ways to Bring the Bill Down
- Set it to 24°C instead of 18°C. Every degree lower makes the compressor work harder. BEE recommends 24°C as the default, and running a few degrees warmer noticeably reduces consumption.
- Use a fan with the AC. Moving air feels cooler, so you can set the AC a degree or two higher and stay just as comfortable.
- Clean the filters every few weeks. Dusty filters reduce airflow and make the AC run longer.
- Close doors and curtains. Keeping sunlight and warm air out of the room means less heat for the AC to remove.
- Use the timer or sleep mode so the AC does not run at full power all night after the room has cooled.
Why Your Bill May Not Match Exactly
Most electricity boards charge in slabs: the first units in a month are cheaper and each higher slab costs more. Bills also include a fixed charge and electricity duty, and rates differ from state to state. So the extra units from an AC can cost more than your average rate per unit, because they push the bill into a higher slab. Check your board's current tariff on your bill or its website.
To see the total for your own home, list your appliances with their wattage and daily hours in our electricity bill calculator below. It adds up the units and cost for each one.