Should You Turn Your AC Off and On, or Let It Run? Here's How to Save on Cooling Costs

Opening a costly utility bill might prompt you to walk to the thermostat and shut off the air conditioner temporarily to save money. However, once the house starts to warm up, you'll likely begin to rethink your decision. You might also consider turning your AC off when you leave the house or during cooler temperatures. However, is it more cost-effective to continuously run your air conditioner at a lower temperature or turn it on and off as the weather fluctuates?

Below, we explain whether it's better to leave your AC running or turn it off and on, as well as how factors such as home size, thermostat settings, and HVAC system type can influence optimal operation for achieving maximum efficiency.

Is It Cheaper to Run Your AC All Day or Turn It Off and On?

While we'd love to provide a simple "yes" or "no" answer to this question, the answer is a bit more complicated. In many scenarios, it's more cost-effective to turn your thermostat up a few degrees while leaving your AC on, rather than try to turn it off and on as temperatures fluctuate. However, many factors determine the best method for managing your home's specific HVAC system.

The potential higher costs associated with completely turning off your AC unit during the day are largely because many HVAC systems must work significantly harder to cool a warm house than to maintain a constant temperature, resulting in increased energy consumption.

Common inefficiencies, such as old windows, poor insulation, and undersized AC units, exacerbate this effect. However, this doesn't mean you should run your AC on full blast, as that can also lead to higher utility bills.

Factors Impacting Your Utility Bill

As previously noted, the decision isn’t as straightforward as a simple 'yes' or 'no.' Whether you should keep your AC running continuously or turn it on and off depends mainly on several key factors.

Thermostat Settings

Leaving your AC running continuously can be cheaper than turning it on and off, but only if you set your thermostat correctly. Even a perfectly sized, properly functioning HVAC unit will struggle to cool a house more than 20 degrees below the outside temperature.

For example, if you set the thermostat to 65°F on a 90°F day, the AC will run nonstop, attempting to cool the house down to a temperature it will never reach. This method of operation puts unnecessary strain on your system and jacks up your utility bill.

In this case, it's better to bump up the thermostat slightly to a realistic temperature to avoid undue strain on your system rather than turning it off completely, which will cause the same strain on the back end as the unit attempts to cool down the hot house. Turning your thermostat up slightly will allow your AC to cycle on and off as necessary rather than running continuously.

Home Size

Larger homes could take longer to heat up throughout the day if you turn your AC off, but they'll also require significantly more energy to cool down once you turn your AC back on. Additionally, the greater surface area on the roof, walls, windows, etc. can lead to more heat gain throughout the day, which will require the AC to work even harder to cool down the house.

HVAC System Type

The type of HVAC system you have might also factor into whether you should run it continuously or turn it off during the day. Here are some common types of HVAC systems and how you should operate each type for optimal efficiency.

• Single-Stage vs. Two-Stage Central Air. In a central air system, the answer might vary depending on whether you have a single-stage or two-stage system. In a single-stage HVAC system, the unit is either on or off. On a two-stage or variable-speed system, the unit can run at a lower speed while maintaining the temperature, rather than actively cooling the house. This means that it's usually cheaper for a two-stage system to maintain a constant temperature than to turn the air off and back on as you come and go. On the other hand, you could save a little money by increasing the thermostat setting on a single-stage unit.
• Ductless Mini-Split. Modern ductless mini-splits are also designed to run at low power while maintaining a constant temperature, allowing you to run the unit continuously without wasting energy.
• Window unit. Window units, especially older models, work similarly to single-stage systems with no variable power. This means they're either on full power or off, meaning you could save money by turning them off or running them at a higher temperature when possible.