Checked 22 Oct 2026
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How much does an AC add to my TNEB bill?
It depends on where your bill already is. A 1.5 ton 3-star inverter AC run 8 hours a night uses about 263 units over a two-month bill. In a home at 300 units, that takes the bill from ₹470 to ₹2,569. In a home that used nothing, the same units cost ₹296.
Work out yours
The two-month units, without what you are adding. Then add what is new.
1.5 ton AC, 3 star inverter
1.5 ton AC, 5 star inverter
Fridge, 242 L frost-free
Ceiling fan, regular
Ceiling fan, BLDC
Geyser, 15 litre
More appliances
Induction stove
Water pump, 1 HP
Iron
LED bulb, 9 watt
Laptop
Wi-Fi router
263 more units in two months
₹2,099
- 1.5 ton AC, 3 star inverter₹2,099263 units: label 878 units a year over 1,600 hours
This takes you past 500 units, so 100 of the free units go and units above 500 cost ₹8.40 or more. Each of these units costs you ₹7.98 on average.
Bills from TNERC's tariff (TNERC Order No. 4 of 2026, 27 Apr 2026, TNERC Order No. 5 of 2026, 26 May 2026), two-month home bill. Appliance figures from BEE labels and makers' specifications, listed below.
In short
- A current 1.5 ton 3-star inverter AC uses about 0.55 units an hour by its BEE label, and a 5-star about 0.43. Run 8 hours a night for two months, that is about 263 and 204 units.
- In Tamil Nadu what those units cost depends on your bill without them: ₹296 from zero, ₹2,099 from 300 units, ₹2,850 from 500.
- The jump comes at 500 units. Cross it and 100 of the 200 free units go, and every unit above 500 is charged at ₹8.40 or more.
- A geyser, induction stove, iron or pump draws 0.75 to 2 units an hour but runs briefly. A fridge uses about 0.73 units a day; a fan 0.03 to 0.05 units an hour.
- Each degree higher on the AC saves about 6%. The 5-star Panasonic model uses about 197 fewer units a year than the 3-star on the label.
The same AC costs different amounts
Tamil Nadu homes pay nothing for the first 200 units in two months if they stay at 500 or under, then ₹4.70 and ₹6.30 a unit. Past 500, only 100 units are free and the rates climb to ₹8.40, ₹9.45 and more. So what an AC costs you depends on what the rest of the house already uses.
The biggest step is between 200 and 300. From 300 units, the AC takes the bill past 500, so it pays for the AC's units at the higher rates and also loses 100 free units on everything else.
TNERC Order No. 4 of 2026, 27 Apr 2026; TNERC Order No. 5 of 2026, 26 May 2026. See the TNEB tariff 2026 for every rate.
Units each appliance uses
| Appliance | Units an hour | Units a bill | At |
|---|---|---|---|
| 1.5 ton AC, 3 star inverter | 0.549 | 263 | 8 hours a day |
| 1.5 ton AC, 5 star inverter | 0.426 | 204 | 8 hours a day |
| Fridge, 242 L frost-free | 0.030 | 44 | 24 hours a day |
| Ceiling fan, regular | 0.053 | 32 | 10 hours a day |
| Ceiling fan, BLDC | 0.033 | 20 | 10 hours a day |
| Geyser, 15 litre | 2.000 | 60 | 0.5 hours a day |
| Induction stove | 1.200 | 72 | 1 hour a day |
| Water pump, 1 HP | 0.750 | 45 | 1 hour a day |
| Iron | 1.000 | 60 | 1 hour a day |
| LED bulb, 9 watt | 0.009 | 3 | 6 hours a day |
| Laptop | 0.030 | 11 | 6 hours a day |
| Wi-Fi router | 0.012 | 17 | 24 hours a day |
"Units a bill" is for 60 days at the hours shown, one of each. One unit is one kilowatt-hour: a 1,000 watt appliance running for an hour. AC and fridge figures are from the BEE star label on one current model each (the fridge is a 2-star model; a 3-star one uses less). The rest are the maker's ratings: rated watts for most, the motor rating for the pump, which draws a little more, and the adapter or power supply rating for the laptop and router, which usually use less.
Panasonic CS/CU-SU18BKY3W, 1.5 ton 3 star inverter split AC (2026), Panasonic CS/CU-NU18BKY5WX, 1.5 ton 5 star inverter split AC (2026), LG GL-N292RDSY, 242 L frost-free refrigerator, Havells Reo Utsav ES ceiling fan, Havells Unnovate BLDC ceiling fan, Havells Orizzonte 15 L water heater, Prestige Xpress induction cooktop, Crompton Mini Master I pump, Philips GC181/80 dry iron, Apple MacBook Air tech specs, TP-Link Archer C6 router.
What an AC really uses
Search results commonly give 1 to 1.8 units an hour for a 1.5 ton AC. The BEE star label works it out differently: a yearly figure over 1,600 hours of use, spread across outdoor temperatures from 24 to 43 degrees by a national pattern in which more than half the hours are at 24 to 28 degrees. That includes the milder hours when an inverter AC slows down. For two current Panasonic 1.5 ton inverter models that gives 0.55 units an hour (3-star, 878 units a year) and 0.43 (5-star, 681 a year).
Your own AC's label shows its yearly figure. Divide it by 1,600 for the hourly average. Chennai is hotter than that national pattern for much of the year, so expect more, especially in April and May.
The temperature you set matters. Each degree higher saves about 6% of the AC's power, the Ministry of Power told Parliament. Since 1 January 2020 star-labelled ACs must come set to 24 degrees, and in March 2025 the electricity board asked homes to run ACs at 24.
Ministry of Power, S.O. 2528(E), 8 Aug 2017 (room AC star labelling); Ministry of Power, S.O. 3897(E), 29 Oct 2019; Lok Sabha unstarred question 2613, Ministry of Power, 27 Dec 2018; Panasonic CS/CU-SU18BKY3W, 1.5 ton 3 star inverter split AC (2026); Panasonic CS/CU-NU18BKY5WX, 1.5 ton 5 star inverter split AC (2026); Asianet Newsable, 3 Mar 2025.
Where the units go, and what cuts them
- Stay at 500 or under. If your bill is close, an hour less of AC a night saves about 33 units a bill, which can keep a home just over the line under 500.
- Set the AC to 24 degrees or higher. About 6% less for each degree.
- Buy 5-star when you replace an AC. The two Panasonic models above differ by about 197 units a year on the label for the same cooling.
- BLDC fans. The two Havells fans above differ by 20 watts, about 12 units a bill each at 10 hours a day.
- Run the geyser only before you bathe. It draws 2 units an hour while heating.
What people report
"Our July bill was double the May bill."
In July 2026 TNPDCL ordered officers to recheck about 3.7 lakh home connections whose use had jumped since May. Nearly 15,000 had crossed 1,000 units and about a lakh were between 500 and 1,000. Officials put it down to a long hot, humid spell and longer AC and cooler use.
"We only added one AC."
One AC can be enough to cross 500 units. Above that line, units over 500 cost more and 100 free units go on the whole bill, so the rise is bigger than the AC's own units suggest. A late meter reading is a separate cause; see how to read your TNEB meter.
Composites of news reports from 2025 and 2026, summarised in our words. We have not named anyone. Sources: DT Next, 29 Jul 2026, NewsBytes, 30 Jul 2026.
Questions people ask
How many units does a 1.5 ton AC use in an hour?
By the BEE star label, about 0.55 units an hour for a current 3-star inverter model and 0.43 for a 5-star one, averaged over a season. The label assumes 1,600 hours a year across outdoor temperatures from 24 to 43 degrees, so on the hottest afternoons it draws more, and on a mild night less. Your own label shows the yearly figure; divide it by 1,600.
How many units does an AC use in 8 hours a night?
About 4.4 units for a 3-star inverter AC and 3.4 for a 5-star, by their labels. Over a two-month TNEB bill that is about 263 and 204 units.
How much does running an AC cost on a TNEB bill?
It depends on your bill without it. The same AC, 8 hours a night for two months, adds ₹296 to a home that was using nothing, ₹2,099 to a home at 300 units and ₹2,850 to a home at 500, because it pushes the bill past 500 units and 100 of the free units go.
How many units does a fridge use a day?
About 0.73 units a day for a 242 litre frost-free double door, by its label of 267 units a year. That is about 44 units on a two-month bill.
How many units does a geyser use?
A 15 litre geyser draws 2,000 watts, 2 units an hour, while it heats, and switches off when the water is hot. Half an hour of heating a day is 1 unit, or 60 on a two-month bill.
How much does a ceiling fan use?
A regular 1,200 mm fan is rated about 53 watts and a BLDC fan about 33. At 10 hours a day that is 32 and 20 units on a two-month bill, so each BLDC fan saves about 12 units a bill.
Does setting the AC to 24 degrees save power?
Yes. The Ministry of Power told Parliament that each degree higher saves about 6% of an AC's electricity. Since 1 January 2020 star-labelled ACs must be set to 24 degrees by default.
Read next
Sources
- Ministry of Power, S.O. 2528(E), 8 Aug 2017 (room AC star labelling). Label energy figure worked over 1,600 cooling hours a year at 24 to 43 degrees outdoors (para 4(3)(i), Table 4.1).
- Ministry of Power, S.O. 3897(E), 29 Oct 2019. Star-labelled room ACs to be set to 24 degrees by default from 1 Jan 2020.
- Lok Sabha unstarred question 2613, Ministry of Power, 27 Dec 2018. Each degree higher on the AC saves about 6% of its electricity.
- Appliance specifications: Panasonic CS/CU-SU18BKY3W, 1.5 ton 3 star inverter split AC (2026), Panasonic CS/CU-NU18BKY5WX, 1.5 ton 5 star inverter split AC (2026), LG GL-N292RDSY, 242 L frost-free refrigerator, Havells Reo Utsav ES ceiling fan, Havells Unnovate BLDC ceiling fan, Havells Orizzonte 15 L water heater, Prestige Xpress induction cooktop, Crompton Mini Master I pump, Philips GC181/80 dry iron, Apple MacBook Air tech specs, TP-Link Archer C6 router.
- TNERC Order No. 4 of 2026, 27 Apr 2026 and TNERC Order No. 5 of 2026, 26 May 2026, for the bills.
- News: DT Next, 29 Jul 2026, NewsBytes, 30 Jul 2026, Asianet Newsable, 3 Mar 2025.
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