Set your thermostat around 78 to 80°F and control humidity, rather than turning the AC off. In Florida's summer, the goal is holding indoor relative humidity below 60 percent, which the EPA says prevents mold. A closed house with the AC off can climb past that fast, so keep it running at a moderate setting while you're gone.
That's the short version, and it goes against the instinct to shut everything down and save on the power bill. On a barrier island in July, an off thermostat is a false economy. Here's the reasoning, and how to actually hold the setting when you're not there to babysit it.
Why "just turn it off" backfires in Florida
Temperature isn't really the enemy in a closed Florida home. Moisture is. When you switch the AC off, two things happen at once: the interior heats up, and the humidity that your air conditioner used to pull out of the air stays in. Warm, damp, still air is precisely the condition mold wants.
The EPA is blunt about the mechanism. It states that the key to mold control is moisture control, and that indoor relative humidity should stay below 60 percent, ideally between 30 and 50 percent. Relative humidity above 60 percent invites condensation and mold growth. A house sealed up with no cooling and no dehumidification in a Florida summer doesn't drift toward that line. It blows past it.
The temperature: moderate, not cold
You don't need to keep an empty house at 72°F. That wastes energy and does nothing extra for humidity. You want a moderate setting that keeps the system cycling.
ENERGY STAR uses 78°F as its baseline summer daytime setpoint, and the Department of Energy recommends keeping the house warmer than normal when you're away rather than shutting the system off. For a closed home, something in the range of about 78 to 80°F is the common practical target: warm enough to save meaningful energy, low enough that the AC still runs often enough to wring moisture out of the air. The exact number isn't magic. What matters is that the system keeps cycling and the humidity stays in check.
One caution from the Department of Energy that applies even to an empty house: don't crank the thermostat to an extreme setting thinking it helps. Setting it colder than normal won't cool faster, and setting it too high lets humidity creep up. Moderate and steady beats extreme in either direction.
The number that matters more: humidity
If you take one thing from this, make it the humidity target, not the temperature. Two houses can both sit at 79°F and be in completely different shape, one at 50 percent humidity and dry, the other at 65 percent and growing mold in the closets.
If your system has a humidistat or you can add a smart thermostat that reads humidity, set it to hold below 60 percent, and aim lower if the house tends to run damp. A standalone dehumidifier plumbed to a drain is a strong backup in closets, laundry rooms, and any space the AC doesn't reach well. The EPA specifically recommends using air conditioners and dehumidifiers to keep indoor humidity down. The point isn't gadgets for their own sake. It's that in Florida, the humidity reading is the health of the house.
How to actually hold the setting while you're gone
A setpoint only helps if the system is still running when you check months later. Plenty of things break the plan: a tripped breaker, a clogged condensate drain that shuts the unit down on a safety switch, a failed capacitor, a power blip that leaves the thermostat off. Any one of those can turn your careful 79°F into a closed 90°F box at 70 percent humidity, and you won't know until you walk back in.
Before you leave, service the system, change the filter, and clear the condensate line so a summer of runtime doesn't clog it. A smart thermostat that reports temperature and humidity to your phone is worth every dollar here, because it turns "I hope it's running" into "I can see it's running." Set alerts for high temperature and high humidity so a failure pings you the day it happens.
When the power blinks and no one's home
The gap a thermostat app can't close is the physical one. When the AC quits in June and the house starts heating and dampening, an alert tells you there's a problem. It doesn't send anyone to fix it. That's the case for a local set of eyes.
Regular home watch visits catch a stalled AC or a rising humidity reading while it's still a same-week fix, not a mold remediation. The visit report notes the interior conditions each time, so a slow trend shows up before it becomes damage. And when the fix needs a technician, a local keyholder can meet the HVAC company and let them in, so the repair happens on the next available appointment instead of waiting for you to fly back. For owners around Fernandina Beach who leave for months at a stretch, that's how a moderate thermostat setting actually stays a moderate thermostat setting.
For the deeper version of the mold side of this, read how to prevent mold in a closed-up Florida home. The thermostat is one lever. Humidity is the one that decides the outcome.
Want someone checking that the AC is still holding while you're away? Learn about home watch or get in touch.