Should You Leave Your AC Running All Day?
When the summer heat hits, many homeowners wonder: Is it cheaper to leave your AC on all day or turn it off while you’re gone?
The answer? For most systems—especially in humid climates like northern Michigan—it’s better to leave the AC on and simply adjust the temperature while you’re away.
Why Turning It Off Costs More
Shutting your AC off completely allows heat and humidity to build up in your home. According to Team Bob’s technicians, that added moisture makes your AC work much harder to remove it once it’s turned back on. That longer run time can actually use more energy than keeping your home at a moderate temperature all day.
How to Handle Different Types of AC Systems
Central Air
For central air systems, the best strategy is to turn the thermostat up 3–5 degrees while you’re out—not off. These systems are designed to maintain consistent temperatures, not to recover from extreme heat and humidity. Letting your home bake all day forces your system to work harder later, increasing wear and energy use. A smart thermostat and regular maintenance can help you save without sacrificing comfort.
Mini Split (Ductless Systems)
Mini splits are more flexible since they cool individual zones and can ramp up quickly. If you’re away for a short time, turning the temperature up is ideal. Even if you’ll be gone longer, it’s still better to leave the unit running at a higher setting. Restarting a mini split in a hot, humid room still puts extra strain on the system and burns more energy.
Window Units
Window AC units don’t handle humidity well and only cool small areas. While it might seem easiest to turn them off when leaving, it’s smarter to use a plug-in timer or smart outlet to reduce the load when restarting. Leaving them running at a higher setting avoids the need for a full humidity purge when you return.
Bottom Line: Don’t Shut It Off
No matter what type of system you have, you should not shut your AC off completely. Keeping it running at a higher setting helps control humidity, maintain comfort, and avoid energy spikes when you turn it back on. For the most efficient results, pair your system with a smart thermostat, clean the filters regularly, and schedule routine AC tune-ups.
Need Help Saving Energy This Summer?
Team Bob’s can help you tune your system, upgrade to smart controls, and make sure your home stays cool and comfortable without wasting energy.
