Having air conditioning at home is a luxury that provides comfort during the hottest months of the year. An ongoing debate exists regarding whether to keep the AC running or turn it off when leaving for work. Many individuals believe that turning off the AC for a few hours is the most energy-efficient and cost-effective approach. Conversely, others argue that maintaining a continuous operation is better to avoid straining the system to rapidly cool the house after it has warmed up during the day.
Three experts interviewed by The Associated Press agree that setting the thermostat a few degrees higher than usual while away is usually the best way to balance energy efficiency with comfort and humidity. Although turning off the AC when away for several hours can save money and energy compared to running it continuously, this method could lead to issues such as mold in humid environments and increased wear on the AC unit, resulting in frequent repairs. Factors like comfort level, the type of AC unit, and building insulation also influence the optimal approach.
Strategies for air conditioning can vary depending on the climate. The U.S. Department of Energy states that adjusting the thermostat by 7-10 degrees Fahrenheit (4-6 degrees Celsius) for eight hours daily can save up to 10% on annual heating and cooling costs. Experts note that numerous considerations are involved in determining the most efficient and economical AC habits.
Elizabeth Hewitt, a professor and urban planning expert at Stony Brook University, emphasizes that turning off the AC for short trips, like a 15-minute grocery store run, does not yield any energy savings. However, for longer absences of around eight hours, it is generally more energy-efficient and cost-effective to turn the AC off.
In some climates, like humid regions, it may not be practical to turn off the AC entirely. Instead, residents can adjust their settings to keep the home at a slightly higher temperature. In dry areas, such as Arizona, homeowners can allow their homes to heat up more by raising the thermostat a few degrees. Conversely, in humid locations like Florida, turning off the AC for extended periods may increase indoor moisture and mold risk since air conditioning helps regulate humidity levels.
Patrick Phelan, a mechanical engineering professor at Arizona State University, notes that bumping up the thermostat by just 1 degree Fahrenheit (0.6 degrees Celsius) can save around 3% in cooling costs. He also points out that leaving the AC off for several hours and then turning it back on may result in more wear and tear, leading to frequent repairs, as these systems take 15 to 30 minutes to achieve optimal efficiency after being powered on.
The effectiveness of energy savings depends significantly on the type of home. While homes made from heavy materials, like concrete or brick, retain cool air longer, older and draftier houses warm up more quickly. For less insulated homes, adjusting the thermostat even for short outings is sensible since indoor temperatures can rise rapidly.
The type of air conditioning unit can also impact energy efficiency. Window units are typically less efficient because they are installed in open windows, making it hard to keep hot air out. Hewitt suggests using foam spray insulation to seal drafty windows, which is a low-cost solution to retain indoor temperatures effectively. Smart thermostats, which learn occupancy patterns and adjust temperatures accordingly, can deliver significant savings. Phelan indicates that switching from a manual thermostat to a smart one, like a Nest, can result in around a 10% energy cost reduction.
Experts recommend simple ways to cool homes without relying solely on air conditioning. These include blocking sunlight, which can help lower indoor temperatures. Henze highlights the benefit of opening windows at night when it is cooler; this tactic, however, may introduce dampness in humid regions that the AC would later need to address. Hewitt adds that closing blinds can also influence indoor temperatures by several degrees, while Phelan points out that some blinds are specifically designed to reflect sunlight, with tinted window films available as another option to reduce heat gain.
