Are You Fighting the Heat with Air Conditioning?

The first anticipated heat wave will lead to widespread use of air conditioning in homes and workplaces, which will also impact electricity consumption and utility bills.

Professor Banjac told RTS that the ideal indoor temperature for living spaces is between 24°C and 26°C.

“The practical recommendation for citizens is to set the thermostat to 25°C and then adjust slightly if they feel uncomfortable, but to start from that baseline,” said Professor Banjac, who is also the Secretary General of the Serbian Committee of the World Energy Council.

He added that this range represents a compromise between energy efficiency, comfort, and the recommendations of the World Health Organization.

In office environments, optimal temperatures depend on the type of activity.

“In shopping centers, temperatures are slightly higher, around 26°C to 27°C, because people are lightly dressed there. These spaces also use centralized air conditioning systems that regulate both temperature and humidity,” he explained.

Proper Use of Air Conditioning

When asked about the correct way to use air conditioners, Professor Banjac said there is no universal rule, as usage depends on external conditions and how long a person stays in the space.

“When we are not staying in a room for long periods, the air conditioner should definitely be turned off,” he said.

However, modern inverter air conditioners operate differently.

“With inverter systems, it is better to leave them running even if you leave the room briefly. They operate efficiently by continuously adjusting the temperature without consuming excessive energy,” he explained.

Older on/off systems, however, should be switched off whenever the room is unoccupied.

Placement of Air Conditioners

The position of the indoor unit is important for both efficiency and comfort.

Since cold air naturally sinks, air conditioners should be installed high enough to allow proper air circulation throughout the room.

“They should not be directed toward areas where people sit - such as desks, dining tables, or sofas. Instead, they should be positioned to avoid direct airflow while still allowing proper air circulation,” the professor said.

Regarding outdoor units, he noted that they should ideally not be exposed to direct sunlight, as this reduces energy efficiency.

Installing outdoor units on rooftops can be a good solution, but there are technical limitations.

“The distance between indoor and outdoor units should not exceed six to eight meters, and there are also limits regarding height differences,” he explained.

“If the unit is placed too high or too low, it can reduce efficiency, increase energy consumption, and in some cases affect system performance. Catalogs may list larger permissible distances, but for attic or top-floor installations, rooftop placement can be acceptable,” he added.

Cleaning and Maintenance

Regular maintenance is important not only for energy efficiency but also for health.

“An air conditioner is not a device you install and forget. It must be cleaned regularly. Large volumes of air pass through it, and dirty filters reduce efficiency and increase energy consumption,” said Professor Banjac.

He recommends cleaning filters every two to three weeks, while a full professional service should be provided once a year.

“Condensation inside the unit can stagnate when the system is not in use, creating conditions for bacteria growth and reducing indoor air quality,” he warned.

Choosing an Air Conditioner

When selecting an air conditioner, one of the key factors is the size of the room.

“Neither an oversized nor an undersized unit is a good solution,” he emphasized.

Energy efficiency ratings should also be considered, particularly seasonal heating and cooling coefficients.

Devices rated A++ are among the most efficient and cost-effective in the long term, he said.

“These devices include additional parameters such as seasonal energy efficiency ratios for heating and cooling. The higher these values, the better, and they are typically associated with A++ class units,” he explained.

Energy Efficiency in the Home

Building efficiency also plays a major role in cooling needs.

Banjac advises lowering blinds during the hottest parts of the day, especially when no one is home, and using nighttime ventilation.

“When outdoor temperatures drop below 20°C, windows should be opened to ventilate the space. These measures can significantly reduce energy consumption,” he said.

He noted that in countries such as Switzerland, air conditioning use is more regulated because buildings are more energy efficient and climatic conditions differ.

The situation in Serbia, however, is different.

“Statistics show that between the 1960s and 1990s, there were only seven to eight tropical nights per year. Today, in the past decade, we have more than 40 such nights annually, so air conditioning has become essential,” he said.

Relocation of Air Conditioning Units

According to the 2023 Planning and Construction Law, outdoor air conditioning units will be gradually removed from building facades.

For public buildings in protected areas, the deadline has already passed (August 4, 2025). For residents in protected zones or buildings, the deadline is 2028, while for all other buildings it is 2033.