Every Arizona summer produces the same question in the same forums: what should I set the thermostat to while I am gone? The answers arrive fast, confident, and contradictory. One neighbour swears by 85. Another says anything above 80 will ruin your furniture.
The uncomfortable truth is that the confident number is the least reliable part of the advice. What actually protects the house is a decision made about your specific property, and a plan for what happens if that decision does not hold.
There is no single magic temperature
The right setting depends on the home, the equipment, indoor materials, plumbing, the belongings left behind and any requirements from an insurer or HOA. A newer, well-sealed house behaves differently from an older home with large west-facing windows and original ductwork.
Humidity matters too, and it does not behave the same across the state or across the season. A setting that keeps a house comfortable in dry June heat is working against different conditions once monsoon moisture arrives.
What is left inside also changes the calculation. Musical instruments, artwork, wine, electronics, leather furniture and stored documents each have their own tolerances, and a house storing any of them is not the same problem as an empty one.
Start with your HVAC professional
Before a long absence, schedule maintenance if it is due, replace filters as appropriate, and ask directly what setting makes sense for that equipment in that property. The person who has seen your system is better positioned than any general rule.
It is worth asking a second question at the same time: what would you expect to fail first on this unit, and what would that look like? An answer to that turns a vague worry into something a home watch visit can actually check for.
The goal is to balance energy use against protection of the home and its systems, and reasonable people land in different places depending on what is inside and how long the house will sit.
Smart alerts help, but they are not a response plan
A connected thermostat can tell you the house is warmer than expected. That is genuinely useful, and worth setting up before you leave — including confirming that remote access works and that alerts reach a phone you will actually look at.
But an alert only tells you something is wrong. It cannot tell you whether the unit has failed, a breaker has tripped, a door was left open by a vendor, or the sensor itself is misreporting. And it cannot do anything about any of them.
You still need someone who can get to the property, confirm the condition in person and coordinate the right vendor. An alert without a local response is an early warning that you are about to spend a stressful week on the phone from another state.
Plan the whole house, not just the thermostat
AC decisions belong beside the rest of the departure plan rather than standing alone. Water shutoff and leak detection, pool care, window coverings, irrigation and storm preparation all interact with how the house holds up while empty.
- Confirm HVAC maintenance and ask about an appropriate setting for your equipment
- Test remote thermostat access and alerts before departure, not after
- Decide your water plan with a qualified plumber, especially for a long absence
- Close or adjust window coverings on the elevations that take afternoon sun
- Confirm pool, landscaping and pest service schedules and who they contact
- Agree in advance who responds, and who can authorise a vendor visit
Decide in advance what counts as urgent
Before you leave, agree on what should reach you immediately rather than appearing in the next routine report. Loss of cooling during extreme heat, active water, signs of forced entry and major storm damage usually belong on that list.
Agreeing on it in advance is what prevents the two failure modes: being called about everything, or being told about the important thing a fortnight late.
Mountain Vista Home Watch provides scheduled interior and exterior checks with photo reporting, key holding, vendor coordination and weather or emergency response for seasonal residents across greater Tucson and the Phoenix metro area.