Leaving Town for the Holidays: What to Set the Thermostat To
A week away is different from a season away. Here are the settings for a short winter trip from a Phoenix house.
For a short winter trip from a Phoenix home, set heating to 55 to 60°F — warm enough to protect plumbing during a freeze, low enough to save meaningfully. Do not turn the system off entirely. Change the filter before you go, and if you have a connected thermostat, set a low-temperature alert and restore the schedule remotely on your way home.
Winter is the easy season to leave
Leaving a Phoenix house in December is far lower risk than leaving it in July. The extreme heat that damages contents is not a factor, and the house will not develop a humidity problem in a dry Valley winter.
The real winter risk is a freeze, and it is a narrow one. Valley overnight lows reach the 30s regularly and drop below freezing occasionally, and plumbing in exterior walls or in an unheated garage is what is actually at stake.
The settings
- Heating to 55 to 60°F. Below 55 starts to risk plumbing in exterior walls on a genuinely cold night. Above 65 is simply paying to heat an empty house.
- Fan on AUTO. No reason to circulate air in an empty house.
- Water heater to vacation mode if it has one, or turn the temperature down.
- Leave interior doors open, particularly to rooms with plumbing on exterior walls, so heat circulates.
- Open cabinet doors under sinks on exterior walls if a hard freeze is forecast.
- Disconnect garden hoses and cover exterior hose bibs. This is the most common freeze damage in Phoenix by a wide margin.
Before you leave
Change the filter. It takes two minutes and means the system is not running on a restricted filter unattended for a week.
Look at the drain pan under an attic air handler. Standing water before you leave means a developing clog, and a week is plenty of time for it to become a ceiling.
If you have a connected thermostat, set a low-temperature alert at around 45 degrees. If the heat fails while you are gone, you want to know — a house dropping toward freezing with nobody in it is the scenario worth preventing.
If you are leaving in summer instead
Different situation entirely, and worth stating because holiday travel is not always December. A Phoenix house left in summer should never be shut off. Set cooling to 85 degrees.
An unconditioned Valley house in July exceeds 120 degrees inside, which damages electronics, adhesives, finishes, wood furniture, and anything with a low melting point. During monsoon, no cooling also means no dehumidification, and a closed-up humid house can develop a microbial problem within a week.
Coming home
If you have remote access, restore the normal schedule a couple of hours before you arrive. Walking into a comfortable house after a long travel day is exactly what that feature is for.
If you do not, resist the temptation to drop the setpoint dramatically the moment you walk in. The system recovers at the rate it recovers, and in winter with a heat pump, a large setpoint jump triggers expensive auxiliary strip heat. Move it in stages.
Frequently asked
What should I set my thermostat to when traveling in winter?
Fifty-five to 60°F for a Phoenix home. That protects plumbing during a freeze while saving meaningfully over your normal setting. Do not turn the system off entirely — Valley lows reach the 30s regularly and occasionally drop below freezing.
Should I turn my HVAC off when I go on vacation?
No. In winter set heating to 55 to 60°F; in summer set cooling to 85°F. A Phoenix house left completely unconditioned in summer exceeds 120°F inside, which damages contents, and in winter risks plumbing during a freeze.
How do I protect my pipes from freezing in Phoenix?
Keep the house at 55°F or above, disconnect garden hoses and cover hose bibs, open cabinet doors under sinks on exterior walls during a hard freeze, and leave interior doors open so heat circulates. Disconnected hoses alone prevent most Valley freeze damage.