The Best AC Temperature to Stay Cool and Save Money

When a heatwave hits, it’s tempting to set the air conditioning as low as it will go. But the lowest setting isn’t the most comfortable — it’s just the most expensive. The real goal is the highest setting that still feels cool enough, because every degree you raise the thermostat cuts cooling costs.

A good starting point: 24–26°C (75–78°F)

For most people in light summer clothing, neutral comfort sits around 25°C (77°F). Many energy agencies recommend setting AC to about 78°F when you’re home. It may sound warm, but with light clothes and a little air movement it feels comfortable — and it dramatically reduces the work your system does versus, say, 21°C.

Why hot weather changes the math

Just as cold walls make you feel colder in winter, hot walls and a sun-baked roof make you feel warmer in summer. After a string of hot days, your home’s surfaces store heat and radiate it back into the room. That means on the hottest days you may need a slightly lower setpoint to feel the same comfort — and on milder days you can set it higher.

Cool smarter, not just colder

Use a fan. Moving air lets you feel comfortable 2–3°C warmer, for a fraction of the energy.
Close blinds and curtains on the sunny side during the day to stop heat getting in.
Ventilate at night. When it’s cooler outside than in, open the windows instead of running the AC — free cooling.
Mind the humidity. Humid air feels hotter; a well-set system that removes moisture can feel cooler even at a higher temperature.

Let the weather decide

The ideal setpoint shifts with the conditions outside. SetMyTemp reads your local temperature, humidity and wind in real time and recommends the setting that keeps you comfortable without overcooling — and it even tells you when simply opening the windows will do the job.

Frequently asked questions

Is 78°F too warm for air conditioning? For most people in summer clothing it’s comfortable, especially with a fan. It’s also far cheaper to run than lower settings.

Does setting the AC very low cool the room faster? No. The room cools at the same rate; a very low setting just makes the system run longer and cost more.

Check today’s recommendation for your city — e.g. Sydney or Los Angeles — with the SetMyTemp tool.