Units per hour, monthly bill and season cost for your AC, from its tonnage and the ISEER on its BEE star label.
Quick answer
An AC's units per hour ≈ cooling capacity in kW ÷ ISEER. One ton of cooling is 3.517 kW. A 1.5-ton AC (5.28 kW) with an ISEER of 4.5 uses about 1.17 units an hour. Run 8 hours a day for 30 days, that is about 281 units, or roughly ₹2,250 a month at ₹8 per unit.
AC electricity cost calculator
Enter your AC's size and the ISEER from its BEE star label to see units and running cost.
Estimate = capacity in kW (1 ton = 3.517 kW) × hours ÷ ISEER. ISEER is a seasonal average, so real use varies with outside heat, room size, insulation and thermostat setting. Your bill also adds slab rates, a fixed charge and duty.
What is ISEER?
ISEER (Indian Seasonal Energy Efficiency Ratio) is the efficiency figure printed on the BEE star label of every AC sold in India. It is measured across a range of Indian outdoor temperatures, so it reflects a whole season rather than a single lab point. A higher ISEER means fewer units for the same cooling. The star rating is set from ISEER bands that BEE revises from time to time, which is why this calculator asks for the ISEER itself.
How to read it off the label
- Look at the yellow BEE label on the indoor unit or the box, or on the model's spec page on the brand's India site.
- The label shows the star rating, the ISEER and the annual energy use in units.
- The annual figure assumes BEE's standard usage pattern. Your own hours will differ, which is why this tool lets you set them.
Ways to cut AC running cost
- Keep the thermostat at 24°C. The Bureau of Energy Efficiency recommends 24°C as the default setting.
- Clean the filters every two weeks in peak summer. Clogged filters make the compressor work longer.
- Size it right. An undersized AC runs flat out for hours. Check with the AC Tonnage Calculator.
- Add up the rest of your home with the Appliance Electricity Cost Calculator.
FAQs
How many units does a 1.5-ton AC use per hour?
About 1.0 to 1.5 units, depending on its ISEER and the heat outside. At ISEER 4.5 the estimate is about 1.17 units.
Does a 5-star AC save enough to justify the price?
Compare the extra price with the yearly saving this calculator shows when you change the ISEER. Heavy users (8+ hours a day, 6+ months a year) recover the difference fastest.
Why is my actual use different?
Room size, sun exposure, insulation, the number of people and the thermostat setting all change how long the compressor runs.