In late October 2026, a post on X about how to set an air conditioner went viral, passing one million views. The routine was simple: run a split AC at 24°C for about half an hour, raise it to 26°C in cool mode with the fan on auto, and switch to sleep mode at night. The result was prepaid electricity credit lasting noticeably longer.
This article explains why that works, for homeowners, facility managers and building owners. The short answer: an AC is most wasteful when it's forced to cool a room far below the outdoor temperature. A 24-26°C setpoint keeps the compressor's load moderate without the room feeling stuffy.
The same principle applies to buildings with VRV or central air-conditioning, where the savings are much larger.
Why does a higher AC temperature save electricity?
Because the cooling load is roughly proportional to the difference between outdoor and indoor temperature. The smaller the gap, the less heat the compressor has to remove.
Heat enters through walls, glass, the roof, gaps around doors and the people inside. In Medan, daytime outdoor temperatures are often above 30°C. A room set to 18°C fights a gap of more than ten degrees, while a room at 26°C fights only a few.
There is a second effect. With a higher setpoint the evaporator runs warmer, which makes the refrigerant cycle more efficient. The compressor removes less heat and uses less electricity for each unit of heat it removes.
How do inverter and non-inverter units differ?
On an inverter AC, the setpoint decides how fast the compressor runs. On a non-inverter AC, it decides how long the compressor stays on.
An inverter compressor adjusts its speed to the load. While the room is still warm it runs fast. Once the target is reached it slows down and holds a low, steady speed, and that is where consumption drops most.
A non-inverter AC has two states, full power or off. The thermostat stops the compressor when the target is reached and restarts it when the room warms up. A higher setpoint gives the compressor longer rests.
This is why the "24°C first, then 26°C" routine feels effective on an inverter unit. The 24°C phase cools the room quickly, and the long hours at 26°C keep the compressor turning slowly. The savings come from the second phase.
Which AC settings matter most?
The setpoint has the biggest effect, followed by the operating mode, fan speed and maintenance.
| Setting | Recommendation | Why |
|---|---|---|
| Temperature (setpoint) | 24-26°C | Smaller gap to the outdoor temperature, lighter compressor load |
| Mode | Cool | Follows the setpoint and still removes moisture; dry mode suits humid weather that isn't very hot |
| Fan | Auto | Fan speed follows the load instead of running at maximum all the time |
| Night | Sleep mode | The setpoint rises gradually while the body needs less cooling |
| Room | Doors and windows closed, curtains on the sunny side | Less heat from outside gets in |
| Maintenance | Clean filters regularly, keep the outdoor unit unobstructed | Good airflow keeps heat transfer efficient |
Setting 16°C doesn't cool a room faster. The unit's cooling capacity stays the same, so only the end point changes, and the compressor keeps working hard to reach a temperature it rarely gets to.
Does 26°C still feel comfortable in a humid climate?
Yes, as long as humidity is under control and the air is moving. Most of the stuffy feeling comes from high humidity rather than temperature.
Cool mode lowers humidity while it cools, because water vapour condenses on the evaporator coil. A fan or ceiling fan running alongside the AC makes the same setpoint feel cooler.
The ASHRAE 55 thermal comfort standard judges comfort from a combination of temperature, humidity, air speed, clothing and activity, not from temperature alone. That is why offices with good air movement feel comfortable at 25-26°C.
What are the rules on AC temperature in government buildings?
Indonesia once regulated AC temperature in government buildings through Minister of Energy and Mineral Resources (ESDM) Regulation No. 13 of 2012 on Saving Electricity Use. That regulation was revoked in 2018 by ESDM Regulation No. 9 of 2018.
While in force, Regulation 13/2012 required government buildings and state- and region-owned enterprises to set temperature and humidity according to the Indonesian National Standard (SNI), and set a 24-27°C range for official residences. At the time, the ESDM ministry also recommended keeping air-conditioned rooms at around 25°C.
For design, the reference is SNI 6390:2011 on energy conservation in building air-conditioning systems. It looks for energy savings without reducing thermal comfort or indoor air quality.
How do you apply this in a building with a VRV system?
In a building, setpoints, schedules and zones are managed from a central controller, so savings don't depend on each occupant's habits.
One VRV system can serve dozens of indoor units. If every room is set to 18-20°C, the outdoor units work far harder than if they were all at 25°C. Common measures:
- Set a standard setpoint, for example 25°C for work areas, and limit the range occupants can select from the room remote.
- Schedule the AC to start shortly before working hours and switch off automatically afterwards, including at weekends.
- Separate zones that are used rarely, such as meeting rooms and halls, so they run only when in use.
- Review the operating history and error codes regularly, because faulty units often run less efficiently.
- Keep filters, coils and the area around the outdoor units clean on a regular maintenance schedule.
Central controller features differ between brands and series, so check the manual for the installed system. If the system shows an error, see our guide to Daikin VRV error codes.
Conclusion
Setting the AC to save electricity comes down to giving the compressor a reasonable load. A 24-26°C setpoint, cool mode, auto fan and sleep mode let an inverter unit run slowly and steadily while the room stays comfortable.
SOKANTARA is an HVAC and MEP contractor headquartered in Medan and working across Indonesia. We design, install and maintain VRV/VRF systems, including setpoint and schedule configuration for government, education and commercial buildings. Contact our team if your building's AC electricity bill looks higher than it should.
References
Sources referred to in this article:
- ESDM Regulation No. 13 of 2012 on Saving Electricity Use (JDIH ESDM)
- Status of ESDM Regulation 13/2012, revoked by ESDM Regulation 9/2018 (pasal.id)
- Mongabay: Government buildings required to save electricity from 1 June (2012, Indonesian)
- SNI 6390:2011, Energy conservation in building air-conditioning systems (National Standardization Agency of Indonesia)
- ANSI/ASHRAE Standard 55, Thermal Environmental Conditions for Human Occupancy
Frequently asked questions
What AC temperature saves the most electricity?
For rooms in a tropical climate, 24-26°C usually gives the best balance of comfort and running cost. Each degree higher narrows the gap between outdoor and indoor temperature, so the compressor works less.
Does starting at 24°C and then moving to 26°C really save power?
The savings come from the long hours at 26°C, not from the 24°C start. Once the room is cool, a higher setpoint lets an inverter compressor run slowly and steadily, which cuts consumption.
Is it fine to use sleep mode every night?
Using sleep mode every night is fine. Sleep mode raises the setpoint step by step while you sleep, when your body needs less cooling than during the day. How far and how often it raises the temperature differs by brand, so check your unit's manual.
Does this apply to central AC and VRV systems in buildings?
The same setpoint advice applies to central AC and VRV systems, and the effect is larger because dozens of indoor units share one system. A central controller holds the setpoints, limits the range occupants can choose and schedules operating hours.
