What Temperature to Set Air Conditioner in Summer

The temperature you set your AC to has a bigger impact on your electricity bill than almost any other factor. Set it too low and you're paying to cool an already-comfortable room. Set it too high and you're uncomfortable. Here's how to find the right balance.

The Recommended Temperature

The U.S. Department of Energy recommends 78°F (26°C) as the ideal summer thermostat setting when you're home and awake. This balances comfort for most people with reasonable energy consumption.

Studies show that every degree you lower the thermostat below 78°F increases your cooling costs by approximately 3–5%. Setting your AC to 72°F instead of 78°F can cost 18–30% more to run.

Recommended Settings by Situation

Why 78°F and Not Lower?

Most people feel comfortable between 72°F and 78°F. The difference in comfort between 72°F and 78°F is small — especially with a ceiling fan running — but the difference in energy cost is significant. A ceiling fan creates a wind-chill effect that makes 78°F feel like 72°F, so you can raise the thermostat without sacrificing comfort.

Factors That Affect Your Ideal Temperature

• Humidity: High humidity makes any temperature feel hotter. In humid climates, running the AC in dry mode or using a dehumidifier can make 78°F feel more comfortable.
• Sun exposure: Rooms with direct afternoon sun heat up faster. Use blackout curtains to reduce solar heat gain and keep the room cooler without lowering the thermostat.
• Activity level: If you're exercising or doing physical work, you'll want it cooler. For sedentary activities like working at a desk or watching TV, 78°F is usually fine.
• Number of people: Each person generates about 250–400 BTU/hour of body heat. More people = warmer room.
• Age and health: Elderly people, infants, and those with certain health conditions may need cooler temperatures. Prioritize their comfort over energy savings.

Should You Turn the AC Off When You Leave?

Don't turn it off completely — set it to 85°F (29°C) instead. Turning it off lets the room heat up significantly, and the AC has to work much harder to cool it back down when you return. Maintaining a higher setpoint while away is more efficient than cycling between off and full cooling.

Use a smart plug with scheduling or a programmable thermostat to automate this. The GHome Smart Plug lets you set a schedule so the AC starts cooling 30 minutes before you get home.

Tips to Stay Comfortable at 78°F

• Run a ceiling fan (raises comfort level by ~4°F)
• Close blinds and curtains during peak sun hours (10am–4pm)
• Avoid using the oven or dryer during the hottest part of the day
• Stay hydrated — dehydration makes heat feel worse
• Wear lightweight, breathable clothing indoors

What About Sleeping?

The ideal sleeping temperature is slightly cooler — around 65–68°F (18–20°C) according to sleep researchers. However, cooling your whole home to 65°F overnight is expensive. A better approach is to use your AC's sleep mode (which gradually raises the temperature as you fall into deeper sleep) or use a fan to create airflow in the bedroom. See our guide on how to use AC sleep mode.

The bottom line: 78°F with a ceiling fan is the sweet spot for most households. Adjust up or down based on your specific needs, but every degree lower costs you money.