top of page

Is It Better to Run AC at Night or Day?

Ensuring your home stays cool and comfortable during the summer can be costly. To cut down on cooling expenses, many homeowners try to minimize air conditioner usage. A common strategy involves opening windows at night to avoid running the AC. However, this raises an important question: Does this approach save money?

Estimated Energy Savings From Turning AC Off At Night

It's not surprising that a central AC system consumes far more energy during the day than at night, especially in hot and humid climates. Typically, about two-thirds of an AC system's energy use occurs between noon and midnight. In cooler climates, such as those found in some parts of South Africa, this can rise to 75% during the daytime due to cooler evenings.

Studies indicate that turning off your air conditioner at night can reduce cooling costs by approximately 30% compared to leaving it on 24/7. However, the actual savings heavily depend on the nighttime temperature and humidity levels.


Adjusting the Thermostat

If the nighttime temperature falls below or matches your thermostat setting, opening windows is generally more effective than running the AC. Conversely, if temperatures remain in the 80s or if it's particularly humid, turning off the AC might not significantly reduce energy consumption.

Factoring In Outdoor Temperatures And Humidity Level

Should the outdoor temperature exceed your indoor thermostat setting, opening windows could make your home warmer rather than cooler. The following day, your AC might need to work harder to recool your home, but this won’t negate the energy savings gained from turning it off at night.

Ac energy

Humidity Level

Humidity is a critical factor. If outdoor humidity levels exceed 65%, it's usually better to keep your windows closed and the AC on. High humidity forces air conditioners to work harder to dehumidify and cool the air when turned on the next morning. In humid conditions, keeping the windows open at night could increase daytime energy consumption by over 20%, potentially offsetting any savings from shutting the AC off.

Expert Cooling Services and More

At Cape Air, we're dedicated to keeping your home comfortably cool during South Africa's warm seasons. With over 15 years of expertise in the local market, our team offers professional heating and cooling services. Our NATE-certified HVAC technicians specialize in a wide range of services including cooling installations, furnace repairs, and AC maintenance for all equipment types. Contact us today to discover your cooling options and learn more about our services.


bottom of page