AC Running Cost Calculator
Estimate what your air conditioner costs a month, and whether a 5-star model pays back.
Air conditioning is usually the single largest item on an Indian summer electricity bill, and the numbers are easy to get wrong because the compressor does not run continuously. This calculator works from tonnage and ISEER, adjusts for your set temperature, and tells you whether a more efficient model would pay for itself.
Your air conditioner and usage
Result
Fill in the fields above and your result will appear here.
What the AC Running Cost Calculator does
ISEER — the Indian Seasonal Energy Efficiency Ratio — is the number on the BEE star label. It measures cooling delivered per unit of electricity consumed, so a higher ISEER means less power for the same cooling. A 1.5 ton unit removes about 5,275 watts of heat; at ISEER 3.8 that needs roughly 1,390 watts of input, and at ISEER 5.2 only about 1,015 watts.
The set temperature matters more than most people expect. Each degree below 24°C raises consumption by roughly 6%, because the compressor spends more time running to maintain a larger temperature difference.
How to use this tool
- Select the capacity of your air conditioner and enter the ISEER from the BEE label on the unit or in the manual.
- Choose inverter or fixed speed. Inverter units modulate compressor speed and average a lower effective draw.
- Enter the hours per day and months per year you actually use it.
- Set the temperature you normally run it at — this changes the answer significantly.
- To compare an upgrade, enter the ISEER of the model you are considering and the price difference to see the payback period.
Formula and method
Cooling capacity = Tons × 3,517 watts
Power at full load = Cooling capacity ÷ ISEER
Temperature factor = 1 + (24 − Set temperature) × 0.06
Duty factor = 0.68 inverter · 0.82 fixed speed
Average power = Power at full load × Temperature factor × Duty factor
Units per day = Average power × Hours ÷ 1,000
Payback years = Extra price ÷ Annual saving
The duty factors reflect that neither type runs at full draw continuously: a fixed-speed unit cycles fully on and off, while an inverter modulates down once the room reaches temperature.
Worked example
Example: 1.5 ton inverter, ISEER 3.8, 8 hours a day at 24°C
| Cooling capacity | 5,275 W |
| Power at full load | 1,388 W |
| Average power after duty factor | 944 W |
| Units per month | ≈ 227 |
| Cost per month at ₹7.50 | ≈ ₹1,700 |
| Over a 5-month summer | ≈ ₹8,500 |
Upgrading to ISEER 5.2 for ₹12,000 more would save roughly ₹2,200 a year — a payback of about 5.5 years, which is marginal unless you run the air conditioner more than eight hours a day.
What your result means
Cost per hour is the figure that changes behaviour. At around ₹7 an hour, leaving the unit running overnight in an empty room is a visible cost rather than an abstraction.
The payback period decides an upgrade. Under four years is a clear case; beyond seven, the unit may not last long enough for the saving to be realised.
The temperature factor is the cheapest saving available. Moving from 21°C to 24°C cuts consumption by nearly a fifth and costs nothing.
Important considerations
- ISEER ratings are revised periodically, so a five-star unit bought several years ago may now correspond to a three-star standard. Compare ISEER values, not stars.
- An oversized air conditioner cycles more and dehumidifies less, which is both less efficient and less comfortable. Match tonnage to room size.
- Dirty filters and coils can raise consumption by 10–20%. Cleaning filters monthly during the season is the highest-return maintenance there is.
- Insulation, curtains and reduced direct sunlight cut running hours more effectively than any efficiency upgrade.
- Running the air conditioner alongside a ceiling fan allows a higher set temperature for the same comfort, and a fan costs a fraction as much.
- Air conditioning often pushes a household into a higher tariff slab, where each additional unit costs more than the average rate.
Limitations of this tool
- It uses a single duty factor for each type. Actual cycling depends on room size, insulation, outdoor temperature, humidity and how often doors are opened.
- ISEER is measured under standard test conditions that rarely match real Indian summer usage.
- It applies a flat tariff and does not model slab pricing — the marginal cost of air conditioning is often higher than shown.
Frequently asked questions
How many units does a 1.5 ton AC consume per hour?
Roughly 0.9 to 1.4 units per hour depending on ISEER, whether it is an inverter model, and your set temperature. A 3-star fixed-speed unit sits at the higher end; a 5-star inverter at the lower.
How much does it cost to run an AC for a month in India?
For a 1.5 ton inverter used eight hours a day at ₹7.50 per unit, roughly ₹1,700–₹2,500 a month. Fixed-speed units and lower temperature settings push it higher.
Is 24°C really better than 18°C?
For cost, decisively. Each degree lower adds roughly 6% to consumption, so 18°C costs around 36% more than 24°C. Most people find 24°C with a fan as comfortable as 21°C without one.
Is a 5-star AC worth the extra money?
It depends on running hours. At eight hours a day the payback is often five to six years; at twelve hours a day it can fall under four. Enter your own figures above rather than relying on the sticker on the showroom floor.