Does Turning Your AC Off When You Leave Save Money?

Anyone who has opened a summer electric bill in Gainesville has wondered if there is a cheaper way to run the AC while they are at work all day. The internet is split on whether to shut it off, leave it running, or set it back - and the honest answer is "it depends on your climate, your home, and your routine." Here is the real picture for Florida.

The Old Advice vs the Florida Reality

The traditional energy-saving advice was simple: cooling an empty home wastes energy, so shut the AC off when you leave. That advice was written by federal agencies for the average US climate, where indoor humidity is not the main problem. In Florida, indoor humidity IS the main problem - and how you handle the AC while you are out determines whether you save money or just shift the cost from cooling to dehumidification when you get home.

What Happens When You Shut the AC Fully Off

With the AC off in a Florida summer, the indoor temperature climbs into the upper 80s within a couple of hours, and indoor humidity rises with it - because warm air holds more moisture, and your home is leaking some of that moisture in through windows, doors, and bath fans. By the time you get home, the AC has to do TWO things at the same time: drop the temperature 10 to 15 degrees AND wring 30 to 50 percent of the moisture out of the air. The compressor runs for a long stretch and the bill saving from the off-hours is largely cancelled by the long catch-up run.

Worse, sustained high indoor humidity over a workday is exactly the condition mold needs to grow. In poorly-sealed homes that habitually shut the AC off for 8+ hours, you can find mold in closets, behind couches, and on baseboards within a couple of summers.

What Happens When You Leave the AC at Your Comfort Setting

Leaving it at 74 degrees all day means the AC short-cycles to maintain temperature even when nobody is home. You are paying for cooling you do not benefit from - the worst of both worlds. This is the version that the old "shut it off" advice was rightly arguing against.

The Florida Sweet Spot: Set It Back 4 to 7 Degrees

The right answer for almost every Gainesville home is a programmable schedule that:

• Holds your comfort setpoint (typically 73 to 76 degrees) when you are home and awake
• Sets back 4 to 7 degrees (so 78 to 82 degrees) when you are out at work or asleep
• Pre-cools 30 to 60 minutes before you arrive home, so you walk in to a comfortable house without the long catch-up run

This pattern keeps indoor humidity from climbing into mold-friendly territory, lets the AC cycle gently rather than running flat-out, and reduces the compressor runtime per day, which is what actually drops the bill. The U.S. Department of Energy estimates a properly-scheduled setback can cut cooling costs by roughly 10 percent annually, though the actual figure depends on your home's tightness and your routine.

Why a Programmable Thermostat Pays for Itself

You can do the setback manually if you remember it every morning and every evening. A programmable thermostat removes the remembering. Smart thermostats add learning (they figure out your typical schedule), geofencing (they set back when your phone leaves a radius around the house), and humidity-aware control on the higher-end models. Most programmable thermostats pay for themselves within a season or two of normal use.

One caveat: not every thermostat works with every AC system. Older single-stage systems, two-stage systems, variable-speed systems, and heat pumps each have different wiring and control requirements. A thermostat that is incompatible can cause short-cycling or refuse to control the system at all. We can confirm what works with your equipment before you buy.

Frequently Asked Questions

Install a Programmable Thermostat With A+ Air Conditioning & Refrigeration

We carry programmable and smart thermostats compatible with most American Standard, single-stage, two-stage, variable-speed, and heat pump systems. Installation is typically under an hour and includes setting up a setback schedule tuned for Florida humidity. Serving Gainesville, Alachua, Ocala, Lake City, High Springs, Bronson, and the surrounding North Central Florida area.

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