Estimate basis: rated draw × star efficiency × usage hours. Add the result to your state-wise bill estimate.
What does the AC electricity calculator tell you?
An air conditioner is usually the single biggest electricity consumer in an Indian home during summer — often 40–60% of the whole month's bill. This calculator turns your AC's basic details — capacity in tonnage, BEE star rating, inverter or fixed-speed type, running hours and days — into three numbers that matter: units consumed per month, average power draw, and the estimated cost at your electricity rate.
You do not need to be an engineer to use it. If you know how many tons your AC is (written on the indoor unit and the outdoor unit's nameplate) and how many hours it runs per day, you can get a realistic monthly figure in under a minute. The result is a planning number: it tells you what share of your state electricity bill comes from cooling, and how much you would save by upgrading, changing usage patterns, or switching to a better star rating.
How your AC bill estimate is calculated
The calculator works in three steps that mirror how an AC actually consumes power. Every air conditioner has a rated draw based on its capacity, an efficiency factor based on its star rating, and a run cycle based on whether it is an inverter or fixed-speed machine.
Tonnage sets the rated power draw
Cooling capacity is measured in tons — 1 ton for small bedrooms, 1.5 tons for average Indian rooms, and 2 tons for large or open living areas. The calculator uses an average rated draw of about 1,200 watts per ton plus a base of 200 watts (the fan, compressor losses and electronics). A 1.5-ton unit therefore starts at roughly 2,000 watts of rated consumption before efficiency is applied.
Star rating adjusts efficiency
The BEE (Bureau of Energy Efficiency) star label gives the AC's seasonal energy efficiency ratio. The calculator applies an efficiency factor per star — 1 star works harder (factor 1.20), while 5 star uses just 0.78 of the rated draw for the same cooling. That is a difference of about 35% between the worst and best rating at identical usage.
Inverter or fixed speed sets the running cycle
Fixed-speed ACs cycle on and off, running near full power most of the time — modelled here at 90% of rated draw. Inverter ACs ramp the compressor down once the room cools, so they average roughly 70% of rated draw over long runs. The longer you run an inverter AC, the bigger that saving becomes.
- Units per month = rated draw × star factor × cycle factor × hours × days
- Estimated bill = units × your electricity rate (₹ per unit)
- Average draw = rated draw × star factor × cycle factor, shown in watts
AC electricity consumption by tonnage and star rating
The table below shows approximate monthly units for 8 hours of daily use at 30 days — the typical summer pattern in most Indian homes. Star rating changes the number far more than people expect:
| Capacity | 2 star | 3 star | 4 star | 5 star |
|---|---|---|---|---|
| 1 Ton | ~285 units | ~256 | ~232 | ~210 |
| 1.5 Ton | ~395 units | ~354 | ~320 | ~290 |
| 2 Ton | ~505 units | ~452 | ~409 | ~371 |
At ₹7 per unit, a 1.5-ton 2-star AC running 8 hours daily costs about ₹2,765 per month, while the same AC as a 5-star costs roughly ₹2,030 — a saving of over ₹700 every month, or about ₹8,000 in one summer season.
Inverter vs non-inverter AC: which actually saves money?
Inverter technology does not reduce the rated draw — it reduces wasted energy. A fixed-speed AC uses a single-speed compressor that starts, runs at full blast, stops, and restarts. Every restart pulls a heavy inrush current. An inverter AC runs the compressor continuously but slows it down to just enough to hold the temperature.
- Inverter ACs shine on long, continuous runs (8+ hours, especially at night)
- Fixed-speed ACs behave similarly for short 1–2 hour sessions
- Inverter ACs also hold temperature more steadily and run quieter
If your usage is short bursts — an hour before sleeping — the premium for an inverter may not pay back. If your AC runs most of the summer night, an inverter is usually the better buy despite the higher sticker price.
How star rating changes your yearly spend
Every extra star improves efficiency by roughly 8–10%, but the real story is cumulative. Take a 1.5-ton AC at 8 hours/day for 6 months of the year: a 2-star burns about 395 units/month (2,370 units in season), while a 5-star burns about 290 (1,740 units). At ₹7/unit that is ₹16,590 versus ₹12,180 — a gap of ₹4,410 per year. The higher upfront cost of a 5-star AC is usually recovered within two summers, after which it keeps paying you.
Why the same AC costs differently in different states
Units are units — but rupees are not. The same 354-unit AC month costs ₹2,478 at ₹7/unit, ₹2,832 at ₹8/unit, and ₹3,540 at ₹10/unit. States with higher slab tariffs (and states where higher consumption pushes you into costlier slabs) will show a much bigger AC footprint on the bill. For the truest picture, run this tool with your state's marginal slab rate from the state-wise bill calculator.
7 ways to cut your AC electricity bill
- Set 24°C, not 18°C — every degree lower adds roughly 6% consumption
- Use the timer — cut the AC off 30 minutes before you leave the room
- Clean the filters monthly — a choked filter can raise consumption 5–10%
- Keep the room sealed — close doors and windows to stop cooled air escaping
- Servicing before summer — a gas-charged, cleaned coil cools faster and cycles less
- Pair with a fan — air movement lets you run the AC a couple of degrees higher
- Use eco/sleep mode at night — ideal for long steady runs
AC electricity calculator FAQs
How many units does a 1.5 ton 5-star inverter AC use per month?
About 230–290 units/month at 8 hours daily — roughly ₹1,610–2,030 at ₹7/unit. Short runs and cooler ambient weather push it lower.
Does an AC consume more in the first minutes?
Yes — startup pulls full power briefly while the room cools. This is why short bursts are inefficient and inverter ACs win on long runs.
Is 1.5 ton AC expensive to run all night?
Eight hours a night for 30 days is roughly 320–410 units for a 3-star 1.5-ton AC — often ₹2,300–2,900/month depending on your rate.
Does a bigger AC use more electricity?
Generally yes, but an oversized AC that short-cycles wastes energy too. Match the tonnage to the room size; 1 ton suits small bedrooms, 1.5 tons most rooms.
Is the AC bill higher at higher slabs?
Yes. The same AC units get billed at your highest slab rate, so an AC month can push the whole bill into a costlier slab.
Can a 5-star AC be cheaper than a 2-star AC over 5 years?
Usually yes — the electricity saving alone exceeds the price difference within about two summers of 8-hour usage.