Set the office AC to 27°C: a saving that costs nothing to try.

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Put in your own numbers

Every figure below then works on your bill. It starts with an example.

Monthly electricity bill₹

AC share of the bill

50%

AC set to today

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24°C

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Try this setting

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27°C

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about ₹19,000 to ₹20,000a month off the AC, 9% of the whole bill

and about 1.4 to 1.5 tonnes of CO₂ a month

An estimate at about 6% for every 1°C, ₹9 a unit and India’s grid average for CO₂, not a promise. Nothing you type leaves this page.

What Japan really does

Japan is the country everyone quotes, and the real story is more useful than the popular version.

• The campaign. Since 2005, Japan’s Ministry of the Environment has run Cool Biz. It encouraged offices to set air conditioning at around 28°C in summer and let staff drop the jacket and tie.³ It was encouragement, not a legal order. The ministry’s 2026 notice names no temperature. It asks people to set the AC flexibly.⁴
• The rule. Japan’s office hygiene standards, under its Industrial Safety and Health Act, set a target range for air-conditioned rooms: 18 to 28°C since April 2022, and 17 to 28°C before that.⁵ This is an effort target for employers.
• The result. The ministry estimated about 4.6 lakh tonnes of CO₂ saved in the first summer, based on a survey of about 1,200 people.³ It is an estimate, not a meter reading.

So 27°C is not Japan’s number. Japan’s number was 28°C, and the office range still stops there. We suggest 27°C because it sits just inside that limit and is easier for people to accept, as long as the room stays dry enough.

Where India stands

• 24°C is the factory default. Since 1 January 2020, star-labelled room ACs up to about 10.5 kW must leave the factory set at 24°C.⁶ You can still change it.
• BEE recommends 24 to 25°C. The Bureau of Energy Efficiency’s 2018 guideline is voluntary, and it is aimed mostly at large commercial premises.¹ So 27°C goes further than BEE asks.
• A 20 to 28°C range has been proposed. The Union power minister proposed it in June 2025.⁷ 27°C sits inside it. We have not found a final notification.
• The building code looks at more than temperature. Indian offices are typically designed for a fixed 22.5°C, give or take a degree.⁸ The comfort method in the National Building Code 2016, as summarised by TERI, also counts air speed and humidity.⁹ By our calculation, 28°C fits it from about 0.5 m/s of air speed at 50% humidity. This is a comfort guide, not a law and not a cap.

Try it · drag your AC along the ruler

Where 27°C sits among the numbers

Japan office range18 to 28°C

India proposed range20 to 28°C

Indian office design21.5 to 23.5°C

BEE recommends24 to 25°C

India factory default24°C

Japan Cool BizAbout 28°C

Suggested here27°C

Your AC today

24°C

1620242830°C

What it saves

BEE estimates about 6% less AC electricity for every 1°C you raise the setting.¹ In an Indian lab test, going from 24°C to 27°C cut AC electricity by 12% to 29% across three units.²

Try it · press the remote, or move the dial

Each degree comes off the AC cost

Set the AC to

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27°C

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Show the lab test

The rupee figures use the numbers at the top of this page, so they are an estimate, not a client result. BEE’s 6% is an estimate, and past 3°C it is rough. Lab results: Kumar et al., AEEE, 2019.²

BEE’s 6% a degree comes to about 17 to 18% for those 3°C, which sits between the lab results.

Your figure will differ. It depends on your tariff, your climate and how your building is used.

• This is a share of AC electricity, not of your whole bill. If AC is 50% of the bill and saves 18%, the bill falls 9%. Five Hong Kong government offices that moved to 25.5°C saved about 1.85% of whole-building electricity per 1°C on average.¹⁰
• These are lab results. We found no field test on working split ACs in India, so measure your own.
• An old AC that cannot reach the set point saves less. On the hottest afternoons such an AC runs flat out at any setting, so the saving is smallest in those hours. Do not count on this alone to cut your Maximum Demand.

How much of your bill is AC?

The saving above is a share of AC units, so what it does to your bill depends on how much of your electricity goes to AC. Published figures vary widely.

The homes row is a peak figure for homes that have an AC. It comes from 11 Hyderabad homes over 19 hot days in May 2019, not a national sample, and it counts only the most used AC in each home, so a second or third AC adds to it. The paper states 39%, and its daily figures, 5.1 of 15.1 kWh, work out to about 34%. Across a full year the share is lower: the study’s AC homes used 15.1 kWh a day in late May and 6.1 kWh in December. Many homes have more than one AC. In that study 10 of 19 AC homes had two or more, and a separate study of 41 homes found 55 ACs in 28 homes.¹⁴ We found no measured figure for Indian offices, and no national figure for Indian factories. A meter on your AC feeder gives you your own number.

Try it · move the slider

18% off the AC is not 18% off the bill

9%off the whole bill: 50% × 18% = 9%

Other electricityAC, still usedAC saved

AC share of your bill

50%

US factories, about 8%Indian AC homes in summer, 39%Indian commercial, about half

What it does for your carbon footprint

Each unit you save also takes CO₂ off your site’s footprint. India’s Central Electricity Authority puts the grid average at 0.675 kg of CO₂ per unit for 2025-26.¹⁵

In the example above, 2,125 to 2,250 units a month comes to about 1.4 to 1.5 tonnes of CO₂ a month, from one setting on the remote.

Try it · set your AC months

Your CO₂ saving in a year

8.6 to 9.1 tonnesof CO₂ a year

2,125 to 2,250 units a month × 0.675 kg × 6 months

Months your AC runs in a year

6

• In a carbon report. Grid electricity counts as Scope 2, so this saving lowers that line.¹⁶ Use your metered units, not this estimate.
• If you have solar. Count only the grid units you save.
• This is an average. It counts generation, not losses in the wires. It also falls as the grid gets cleaner: it was 0.774 kg in 2013-14.¹⁵

Why humidity decides it

A thermometer alone does not tell you how a room feels. Moisture and moving air matter too. 27°C in dry heat feels easy. 27°C in sticky weather feels warmer, and the room can turn damp.

Two numbers get mixed up here. Humidity, in %, says how close the air is to holding all the water it can at its present temperature, so it moves when the room temperature moves. Dew point, in °C, says how much water is really in the air, so cooling the air does not change it. The same air reads 48% at 27°C and about 57% at 24°C, and its dew point stays 15°C.

For a room at 27°C, the humidity reading is all you need. Aim for about 48%, and 51% at most. At 28°C, aim for about 45%. Those readings are a dew point of about 15 to 16°C, the number engineers use.¹⁷ ASHRAE treats an indoor dew point that stays above about 15°C for days as an early warning of damp.¹⁸

Try it · move the slider

What your logger reading means at 27°C

48%humidity at 27°C, a dew point of 15°C

Too dryAimWatchStep back

30%40%48%60%70%

Logger reading

Good. The room is dry enough to hold 27°C.

The same city can change type. Delhi in May is dry heat, and Delhi in the monsoon is humid. We found no measured saving figure for the Gulf, so we give none.

How to make 27°C work

1. Run the fans. By our calculation, 28°C with air moving at about 0.4 to 0.65 m/s feels like 26°C in still air. Fans cannot make 28°C feel like 24°C in still air. That needs 1.45 to 2.15 m/s, and the ASHRAE 55 comfort standard stops at 0.8 m/s, or 1.2 m/s if people control the fan.⁹
2. Change in steps. Go up 1°C at a time and hold each step for at least two weeks. People can take up to 3 months to settle.²¹ If a team is uncomfortable, go back a degree. A setting people accept will last longer than one they keep changing back.
3. Relax the dress code. Cool Biz paired the higher setting with lighter clothes for this reason. By our calculation, lighter clothes are worth about 2 to 3°C.
4. Measure humidity. Put a temperature and humidity logger at seated height. Stay at or below 48% at 27°C, or 45% at 28°C. If the room stays near 60% for days, step back a degree. A few damp hours are no reason to act.
5. Set the indoor fan to AUTO. Do not run fan-only mode. When the compressor stops, a running fan can blow the water on the coil back into the room.²²
6. Seal the room. Keep doors and openings closed while the AC runs, so damp outside air stays out.
7. Check the room, not the remote. Judge by the temperature the room actually reaches.

Try it · turn up the fan

Fans buy you about 2°C, and no more

Air speed

0.05 m/s

Still airFan onToo far

Feels-like figures are our calculation, for 28°C air. ASHRAE 55 limits as summarised by TERI.⁹

Keep the filter and coil clean

Try it · choke the filter, then wash it

What a choked filter really costs

Dust on the filter

0%

Wash the filterHottest afternoon

100 is an index, not a reading from a real AC. About 10% is our judgement from four sources that used different methods.^{23, 24, 25, 26} The line from clean to choked is drawn straight, for illustration.

• Filter. Clean a split AC’s filter about every two weeks. A truly choked filter uses about 10% more electricity for the same cooling, in a range of 5 to 15%. That is not a promise on your bill: when the AC is already flat out at peak, the loss shows up as a warmer room, not more units.
• How to wash it. Switch off the power and vacuum first. Wash in water below 40°C²⁷, with neutral detergent if the dust stays. Dry it in the shade and refit it tightly. Never run the AC without its filter.
• Coil. Have it checked once a year. If it is dirty, get a trained technician to wash it before summer. A dirty coil can cost far more than a dirty filter.²⁵
• No sprays. Do not use cleaning sprays, alcohol or bleach inside the unit.²⁸ NITE, Japan’s product safety agency, counted 20 fires in five years from wrong internal cleaning.²⁹
• Jet wash. Allow it only with the breaker off, and with the circuit board, display and fan motor covered. Keep the pressure low so the fins do not bend. Foam goes only on the coil and must be fully rinsed out. Afterwards, check the drain and test the cooling.
• Drain. Keep the pan and the drain line clear.
• Stop and unplug if you notice a burnt smell, no control, abnormal noise or a water leak.

Bring in fresh air

Most wall-mounted ACs bring in no fresh air. They cool the same room air again and again, so a closed room slowly fills with the CO₂ people breathe out. The WHO says to open windows for a few minutes every hour.³⁰ Singapore’s National Environment Agency says to reduce or turn off the AC while they are open.³¹

A CO₂ meter is a simple check. Aim for no more than about 1,000³² to 1,100³¹ ppm. In a fully sealed room, the worst case, our calculation gives these times to reach 1,000 ppm:

Try it · build your own room

How fast a sealed room reaches 1,000 ppm

Meeting roomCabinOfficeYour room

People

12

Room size

150 m³

Meeting roomCabinOffice

The worst case: a fully sealed room with no leaks, seated adults, 430 ppm outdoors. Our calculation, not a measurement.

• In dry heat, open up at dawn. The outside air then cools the room for free.
• In humid weather, outside air brings in mostly moisture, so keep the opening short. If you add a fan, choose one that supplies filtered air. An exhaust fan alone pulls damp air in through the cracks.
• When outdoor air quality is poor, avoid opening up.

To flush a room with a fan, plan on three room volumes: hours = 3 × room volume ÷ fan m³/h. A 300 m³ room with a 1,000 m³/h fan takes 54 minutes.

Prove it on your own meter

A saving you cannot see does not last. Someone picks up the remote, sets 22°C, and the money quietly goes back out.

Put a meter on the AC feeder. Record two weeks at your usual setting. Step up as above, record two weeks at the new setting, and compare days with similar outdoor weather. KONDUKTOR® EMS shows that feeder’s units for every day, so the saving is on your screen, in your building. If someone turns it back down, you see it in that day’s units, not on next month’s bill.

Try it · you hold the remote

The saving, and the day it comes back

Remote

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24°C

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Pause

Illustration, not a client result. It starts at about 500 units a day at 24°C and moves about 6% for every 1°C.

Your plan

This comes from what you set on this page. Change a figure and it updates.

Sources

Some of these we could read only as an abstract or a summary. Anything marked “by our calculation” is ours, and so are the rupee example and the choice of 27°C.

1. BEE gives the 6% as an estimate and shows no test behind it. Bureau of Energy Efficiency, recommended guidelines, 25 June 2018 (archive copy)
2. The test covered three split ACs of about 1.4 to 1.5 TR in an accredited Indian lab. Kumar et al., AEEE, eceee Summer Study 2019 (the lab test)
3. This is the ministry’s own report on the first Cool Biz summer. Japan Ministry of the Environment, Cool Biz press release, 28 October 2005
4. The 2026 notice names no temperature. Japan Ministry of the Environment, Cool Biz notice, 2026
5. This report covers the lower limit moving from 17 to 18°C. Rodo Shimbun, Japan office standards change to 18 to 28°C, February 2022
6. This report came as the rule took effect. Mercom India, 24°C factory default for ACs, January 2020
7. We read this report through an archive copy. The Print, 20 to 28°C proposal, September 2025
8. This study records the 22.5°C design norm. Manu et al., India Model for Adaptive Comfort, 2016
9. TERI summarises the code’s method. We did not read the code itself. TERI, Thermal Comfort Prescription (National Building Code 2016 method, ASHRAE 55 air speed)
10. The paper compares monthly units for 2004 and 2005, adjusted for working hours, weather and activity. EMSD Hong Kong, 25.5°C and human comfort
11. This is the Planning Commission’s figure, as quoted by Brookings. Brookings, The future of Indian electricity demand, 2018 (citing the Planning Commission)
12. We read this paper in full. Ramapragada et al., AC load patterns in Indian homes, Energy Informatics, 2022
13. The share covers building heating, cooling and ventilation in US manufacturing. US EIA, electricity use in manufacturing
14. This study used bills and interviews from homes in Hyderabad and Jaipur, not meters. Gupta et al., electricity use in Indian dwellings with and without AC, 2025
15. This is the grid’s weighted average, at generation, including renewables and captive power. Central Electricity Authority, CO₂ Baseline Database for the Indian Power Sector, Version 22.0, August 2026
16. Scope 2 covers purchased electricity. GHG Protocol, Scope 2 Guidance
17. This addendum limits indoor dew point to 15°C when the outdoor dew point is higher. ASHRAE, Standard 62.1 addendum ae (indoor dew point)
18. ASHRAE calls this an early warning, not proof of damp. ASHRAE, Damp Buildings guide, 2020
19. These slides summarise ISHRAE’s guidance. We did not read the original. ISHRAE guidance, Prof. Mathur’s slides (humidity floor, climate)
20. Dubai’s utility advises 24°C or higher. We read only an excerpt. DEWA, set your AC to 24°C
21. This guide asks for at least two weeks at each step. CBE, Fans Guidebook (steps and settling time)
22. A running fan puts water from the coil back into the air after the compressor stops. Henderson, Shirey and Raustad, moisture back into the room, 2003
23. On a 1 TR split AC, 46.7% less air over the indoor coil cost 9.6% of its efficiency. Mohammed and Nasser, Journal of Engineering and Sustainable Development, 2017
24. A fully plugged filter on a wall split AC cost 11.19% of its efficiency. We read the abstract only. Journal of the Faculty of Engineering and Architecture of Gazi University, 2012
25. This is a calculation from one large unit, not a test. It gives about 9% more energy with a very dirty filter and about 20% with a dirty coil. Oak Ridge National Laboratory, ORNL/TM-9894 (fouling)
26. Mitsubishi’s own test found power about 12% worse after about half a year without cleaning. Its method is not published. Mitsubishi Electric, filter and electricity, 2023
27. Daikin’s owner care page also says to switch off at the breaker first. Daikin Japan, filter care
28. Hitachi warns that residue can break resin parts and cause smoke or fire. Hitachi, cleaning spray advice
29. This is NITE’s own count. NITE Japan, AC cleaning fires, 25 June 2020
30. The WHO also says most wall and window units do not provide ventilation. WHO, ventilation and air conditioning Q&A
31. Singapore’s limit is 700 ppm above outdoor air, about 1,100 ppm. Singapore NEA, CO₂ monitoring advisory
32. Japan’s limit is 1,000 ppm. We read it through city pages that quote it. Japan MHLW, building hygiene standard (CO₂ 1,000 ppm)