What temperature do I set my A/C to when I’m on vacation?

If you’re going on vacation for any extended period of time, don’t turn your air conditioner off. Instead, set the thermostat to 85° Fahrenheit and make sure the thermostat fan is set to AUTO, not ON.


Well, setting your thermostat to 85 degrees and your thermostat fan to AUTO means your AC will run long enough to remove extra humidity in your home but not enough to make your energy bills skyrocket.

Let’s look at how your AC removes humidity and why extra moisture is so dangerous for your home in the first place.

How your AC removes humidity from your home

As your air conditioner cools the air in your home, it also strips the air of extra moisture.

You see, your AC unit has what’s called an evaporator coil. The evaporator coil sits inside the indoor air handler unit and is basically an A-shaped web of super cold refrigerant-filled coils.

central air conditioner evaporator coil
What your evaporator coil looks like.

Those cold coils absorb both heat and moisture from the air. And, over time, moisture builds on those coils and drips away outside via a “condensate drain”. The more moisture that exits the home via the condensate drain, the less indoor humidity your home will have.

But keep in mind, if you set your thermostat fan to ON, the dehumidification process can’t happen.

Keep your thermostat fan set to AUTO, not ON.

When your thermostat fan is set to ON, the fan runs constantly (even when the AC isn’t cooling). Which means the fan is blowing all the moisture on your evaporator coils right back into your home. Leaving the fan set to ON can also cause your energy bills to skyrocket, unfortunately.

But if you keep your fan set to AUTO, the fan only runs during cooling cycles. Which means, when the fan stops running, the moisture on your evaporator coils has time to drip off and drain away outdoors.

So now that you know how your AC removes humidity, let’s look at why your home needs to be dehumidified while you’re on vacation.

Why high indoor humidity is bad for your home

If you turn your AC off completely or set your thermostat fan to ON while you’re away for vacation, you can expect the humidity levels in your home to soar in a matter of hours.

And high indoor humidity can lead to:

  • Mold and mildew growth
  • Structural damage to your home

Mold and mildew growth

According to the EPA, indoor humidity over 60% creates enough humidity for mold and mildew growth.

And, unfortunately, your home contains all kinds of surfaces that are perfect for mold growth, including:

  • Counter-tops
  • Ceilings
  • Carpets
  • Wallpaper
  • Insulation
  • Drywall
  • Fabric
  • Upholstery
  • Etc.

Structural damage to your home

Wood that’s exposed to high amounts of moisture can warp and bend over time. Elements of your home that can be damaged due to high humidity include:

  • Floorboards
  • Window panes
  • Doors
  • Walls
  • Wooden furniture

So if your AC isn’t dehumidifying your home while you’re away on vacation, you could come back to a home with dangerous and expensive structural damage.

Need more indoor air quality tips? Ask a Kansas City tech

At Santa Fe, we’re always happy to share our AC expertise with you.

If you have a specific question, just check out our help guides or contact us directly.