WHO shares AC-and-fan cooling formula for your room that can cut electricity bill by 70% and give comfortable sleep as well

With temperatures rising unusually early in many parts of India and heatwave warnings already being issued, people are looking for ways to stay cool at night without seeing a spike in electricity bills. Cooling the room has become less about comfort and more about health, especially as nights are also getting warmer. In this situation, the guidance shared by the World Health Organization (WHO) offers a simple way to use AC and fan together more efficiently.

Why heat is becoming a serious health issue

Heat is no longer just about discomfort. WHO has flagged it as a major environmental and occupational hazard. It says heat stress is the leading cause of weather-related deaths globally and can worsen existing conditions like cardiovascular disease, diabetes, asthma and mental health issues.

The data gives a worrying picture. Between 2000 and 2019, around 4.89 lakh heat-related deaths occurred every year worldwide, with a large share in Asia. Among older adults, the impact has increased sharply, with heat-related mortality rising significantly over the years.


Heatwaves are also becoming more frequent and intense due to climate change. Cities face an added problem where buildings and roads trap heat, making both days and nights warmer.

The problem with hot nights

It is not just daytime heat that creates risk. Studies published on ScienceDirect highlight that hot nights can increase the risk of death considerably. In some cases, mortality risk on hot nights can be up to 50% higher than on normal nights.

The reason is that the human body does not get enough time to cool down. When nights remain hot, the body continues to stay under stress, which can affect vital organs like the heart and kidneys. Research also shows that hot nights following extremely hot days are even more dangerous.

WHO’s AC and fan formula

Amid these conditions, WHO has suggested a simple method many people overlook. It says that when using air conditioning, the thermostat should be set to 27°C and an electric fan should be used at the same time. This combination can make the room feel about 4°C cooler and may reduce electricity consumption for cooling by up to 70%.

The idea is practical. The AC works less aggressively at a moderate setting, while the fan helps distribute the cooled air across the room more evenly.

WHO also cautions that fans should not be used when temperatures cross 40°C, as they may end up circulating hot air and heating the body instead of cooling it.

The guidance also talks about everyday steps that can help keep indoor spaces cooler. During the day, windows should be kept closed and covered to block direct sunlight. At night, windows can be opened to let cooler air in if the outside temperature drops.

Reducing the use of electrical devices can also lower indoor heat. Wearing loose clothing, using light bedding and taking cool showers are small steps but can help the body handle heat better.

Why this matters right now

With the India Meteorological Department indicating that high temperatures are likely to continue in several regions, these measures become more relevant. Health experts have advised people to stay hydrated, avoid going out during peak heat hours and watch for signs of heat-related illness.

In simple terms, running the AC at very low temperatures for long hours is not always the best solution. A balanced approach, like the one suggested by WHO, can help people sleep more comfortably at night while also keeping electricity use under control.