Setting the temperature too low

Many people lower their air conditioners to 17 degrees Celsius or 18 C, believing they can cool a room quickly before switching the unit off to save electricity. However, experts say this approach often uses more energy than maintaining a moderate temperature.

Mark Goldsworthy of Australia's CSIRO, which researches air-conditioning systems and conducts energy-efficiency testing, told The Conversation that cooling a room to an unusually low temperature requires a large amount of energy.

"While running it briefly and intermittently at a very cool temperature may feel thrifty, it won’t be the most energy efficient choice."

Mariam Gabaji, a utilities expert at Finder, told Yahoo Lifestyle that the most cost-effective setting is typically between 24 C and 26 C. She said each degree below that range can increase energy consumption by about 10%, making moderate settings a more economical choice.

A person sets air-conditioning temperature. Photo from Pixabay

Cooling unused rooms

Trying to cool an entire home can place unnecessary strain on an air-conditioning system.

Experts recommend focusing on frequently used spaces such as living rooms and bedrooms. Cooling a smaller area allows the system to operate more efficiently and reach the desired temperature faster.

Dereck Granados, an air-conditioning and refrigeration instructor at Universal Technical Institute in the U.S., told lifestyle magazine Homes & Gardens that homeowners often leave interior doors open, allowing cool air to flow into empty rooms.

Closing doors to rarely used spaces can reduce energy waste at no cost. Windows and exterior doors should also remain closed while the air conditioner is running.

Leaving curtains and blinds open

Sunlight entering through windows can significantly raise indoor temperatures, forcing air conditioners to work harder.

Granados said many people focus only on lowering thermostat settings while overlooking ways to reduce heat entering the home. He recommended closing blinds during the hottest parts of the day or installing heat-reflecting window films.

Thermal blackout curtains can also help block sunlight in summer while providing insulation during colder months. For a longer-term solution, planting trees or shrubs near windows can reduce solar heat gain and provide additional privacy.

Ignoring maintenance issues

Unusual noises, uneven cooling and unexpectedly high electricity bills can all indicate problems with an air-conditioning system.

Lisa Purvins, chief financial officer and vice president of U.S.-based refrigeration company Pro-Tech Heating & Cooling, told lifestyle news site Real Simple that many homeowners ignore early warning signs until a major breakdown occurs. She said minor issues are often inexpensive to repair when detected early but can become far more costly if left unresolved.

Experts recommend scheduling maintenance checks before summer and winter. Routine inspections can identify problems such as dirty coils, low refrigerant levels or electrical faults before they affect performance and efficiency.

Relying only on AC

Many homeowners overlook fans because they already have air conditioning, but combining the two can reduce energy use.

Mark Woodruff, senior product manager at HVAC manufacturer Trane, told Homes & Gardens that fans can make people feel up to four degrees cooler through the wind-chill effect. As a result, homeowners can remain comfortable while setting thermostats slightly higher.

When using ceiling fans, experts also recommend ensuring they rotate in the correct direction during summer to circulate cool air effectively and avoid wasting energy.