Should I Leave My AC On While On Vacation?

When It Makes Sense

• Good fit: You live in a region with extreme summer heat where indoor temperatures can exceed 90°F, and your home contains sensitive electronics, wooden flooring, or musical instruments that could be damaged by prolonged heat.
• Good fit: You have a smart thermostat that can maintain a modest setback temperature (e.g., 78°F) and you want to keep humidity under control to prevent mold growth during a two‑week trip.

When You Should Avoid It

• Warning sign: Your home is poorly insulated, you have an older, inefficient AC unit, and the electricity rates in your area are high, making run‑time costly and environmentally wasteful.
• Warning sign: You will be away for an extended period (a month or more) and have no reliable way to monitor the system, increasing the risk of a malfunction that could cause water damage.

Pros and Cons

Pros

• Prevents heat‑related damage to furniture, electronics, and structural components, especially in hot climates.
• Maintains a more stable indoor humidity level, reducing the chance of mold or mildew after a long absence.

Cons

• Increases electricity consumption, which can raise utility bills and carbon footprint, particularly with older units.
• Running the system unattended raises the likelihood of a mechanical failure that could cause water leaks, frozen coils, or loss of cooling.

Decision Checklist

• What is the typical outdoor temperature during your vacation period, and will it push indoor temps above a safe threshold for your belongings?
• Do you have a programmable or smart thermostat that can set a safe setback temperature and alert you if the system deviates?
• Is your AC unit regularly maintained, and do you have a trusted service provider who can respond quickly to emergencies?

Alternatives to Consider

Instead of leaving the AC running continuously, you might: set a modest setback temperature (e.g., 78‑80°F) that balances protection and savings; use ceiling fans or portable evaporative coolers in occupied rooms before you leave; install window film or shade to reduce solar gain; or invest in a smart home monitoring system that can turn the AC back on if indoor temperatures exceed a preset limit.

Final Recommendation

For most homeowners, the safest middle ground is to use a programmable or smart thermostat to maintain a modest setback temperature while you’re away, combined with good insulation and humidity control. This approach protects your home without the expense and risk of running the AC at full capacity. If you have an older, high‑energy‑use unit or will be gone for a month or more, consider turning the AC off and relying on passive cooling methods, but arrange for a trusted neighbor or professional to check the system periodically. Always consult an HVAC professional if you have concerns about equipment health or local energy‑efficiency incentives.