What Temperature Should You Set Your AC in Phoenix?
What temperature should I set my AC in Phoenix?
Phoenix summers can put your air conditioner under significant workload. The right thermostat setting can help balance indoor comfort and energy use.
For many Phoenix households, 78°F is a useful starting point when you're home, while SRP currently recommends 78–80°F while at home and up to 85°F when away for energy savings.
However, there isn't one temperature that works perfectly for every household. Your home's insulation, AC condition, sunlight exposure, occupancy, and personal comfort all affect the ideal setting.
Phoenix homeowners rely heavily on their air conditioners during Arizona's hot season. Because cooling can account for a substantial portion of summer electricity use, thermostat settings can have a noticeable effect on both comfort and energy consumption.
So, what temperature should you set your AC in Phoenix?
A practical starting point is:
78°F–80°F when you're home
Around 80°F–85°F when you're away
Adjust the temperature based on comfort, household needs, and your home's ability to maintain the setting.
SRP specifically recommends 78–80°F while at home and up to 85°F when away.
The U.S. Department of Energy has also used 78°F as a summer energy-saving reference point and notes that raising the thermostat can reduce cooling costs.
What Temperature Should Your AC Be in Phoenix?
For many households, 78°F is a reasonable starting point during occupied hours.
If 78°F doesn't feel comfortable, you can adjust the thermostat gradually rather than immediately setting it extremely low.
For example:
Situation | Starting Temperature |
Home during the day | 78–80°F |
Home and especially sensitive to heat | 76–78°F |
Away for several hours | 80–85°F |
Away for an extended period | Up to 85°F |
Sleeping | Adjust to your comfort |
These are starting points, not mandatory settings. SRP recommends 78–80°F while home and up to 85°F while away.
Why 78°F Is a Common Summer Setting
Setting your thermostat at 78°F doesn't mean your AC won't keep your home cool.
The thermostat tells the system the indoor temperature you want maintained.
If your thermostat is set to 78°F, the AC will operate as needed to maintain that temperature.
The important consideration is the difference between your indoor and outdoor temperatures.
During a Phoenix heat wave, the outdoor temperature can be dramatically higher than your indoor thermostat setting. Lowering the thermostat several additional degrees can require the system to operate longer.
The Department of Energy notes that setting a thermostat to 78°F instead of 72°F can reduce cooling energy use by roughly 6–18%, depending on conditions.
What Temperature Should You Set Your AC When You're Home?
A good starting range is:
78°F–80°F
This range is consistent with SRP's current Arizona summer energy-saving guidance.
If you're comfortable at 80°F, you may be able to reduce cooling demand further.
If 80°F is uncomfortable, try 78°F and adjust from there.
You can also use ceiling fans to improve how cool the room feels. APS notes that fans can make occupants feel cooler without requiring the thermostat to be lowered.
Important:
A ceiling fan cools people, not the room itself. Turn it off when nobody is using the room.
What Temperature Should You Set Your AC When You're Away?
If you're leaving home for several hours, you generally don't need to maintain the same temperature you use while you're there.
A setting around:
80°F–85°F
can reduce unnecessary cooling while the house is unoccupied.
SRP recommends up to 85°F when away for maximizing energy savings.
APS also advises that homeowners leaving for longer periods during summer can set the thermostat as high as 85°F, then begin cooling the home before returning.
Should You Set Your AC Lower at Night?
This depends largely on your household's comfort preferences.
Some people prefer a cooler bedroom while sleeping, while others are comfortable with a higher thermostat setting.
Rather than automatically setting the thermostat extremely low, try adjusting it gradually.
For example:
78°F → 77°F → 76°F
and see what provides adequate comfort.
There's no requirement that every Phoenix household use the same nighttime temperature.
Does Setting Your AC to 70°F Cool Your House Faster?
Not necessarily.
If your home is 85°F and you set the thermostat to 70°F, the AC doesn't necessarily cool the house faster than if you set it to 78°F.
The system still has to remove heat from the home.
Setting the thermostat significantly lower can instead result in the system running longer as it attempts to reach the lower target.
A better approach is to choose a reasonable temperature and allow the system to maintain it.
Why Setting Your AC Too Low Can Increase Cooling Costs
The lower the indoor temperature you demand, the greater the cooling load can become.
For example:
Outdoor temperature: 110°F
Thermostat | Temperature Difference |
80°F | 30°F |
78°F | 32°F |
75°F | 35°F |
72°F | 38°F |
The AC has to continuously remove heat entering the home.
That's one reason Phoenix homeowners can benefit from avoiding unnecessarily low thermostat settings.
APS says that raising the thermostat by 1°F can save approximately 2–3% on cooling costs.
What If Your AC Can't Maintain 78°F?
This is an important section for your lead-generation strategy.
If your thermostat is set to 78°F, but your home consistently remains at:
82°F → 84°F → 87°F
during normal operation, there may be an underlying problem.
Possible causes include:
1. Dirty Air Filter
A clogged filter restricts airflow and can make the system work harder.
2. Dirty Outdoor Condenser
Dust and debris around the outdoor unit can restrict heat transfer.
3. Refrigerant Problems
Low refrigerant or a refrigerant leak can affect cooling performance.
4. Poor Airflow
Blocked vents, duct problems, or other airflow restrictions can prevent conditioned air from reaching rooms properly.
5. Poor Insulation
Heat entering through the attic, walls, windows, or doors can increase the cooling load.
6. Undersized AC System
If the system isn't properly sized for the home, it may struggle during extreme outdoor temperatures.
7. Aging Equipment
Older systems can become less efficient and may have difficulty maintaining comfortable temperatures during extreme heat.
What If Your AC Runs Constantly?
Phoenix AC systems may run for extended periods during extremely hot weather.
However, if your AC seems to run continuously and cannot reach the thermostat setting, it's worth having the system evaluated.
Don't automatically assume that the thermostat needs to be lowered.
For example:
If your AC is set to 78°F but the home remains at 84°F for hours, lowering the thermostat to 72°F won't necessarily solve the underlying problem.
The issue may be equipment performance, airflow, ductwork, insulation, refrigerant, or another component.
Use a Smart Thermostat to Manage Phoenix Cooling
A programmable or smart thermostat can help automate temperature changes throughout the day.
For example:
When home:
78–80°F
Before leaving:
80–85°F
Before returning:
Automatically begin cooling the home.
APS recommends using smart thermostats to manage schedules and also discusses pre-cooling for customers on certain time-of-use plans.
Should Phoenix Homeowners Pre-Cool Their Homes?
Pre-cooling can be useful for some homeowners, particularly those on time-of-use electricity plans.
The basic idea is:
Cool the house before higher-cost periods → raise the thermostat during those periods.
For example, APS describes pre-cooling before its specified on-peak period for applicable time-of-use customers, then raising the thermostat during the peak window.
Your exact schedule should depend on your utility plan.
Other Ways to Keep Your Phoenix Home Cool
Your thermostat isn't the only factor affecting indoor comfort.
Change your air filter regularly
APS recommends monthly filter changes as one way to improve AC performance and efficiency.
Keep doors and windows closed
Don't allow hot outdoor air to enter while the AC is operating.
Use ceiling fans
Fans can improve perceived comfort and may allow you to use a somewhat higher thermostat setting.
Block direct sunlight
Close blinds or curtains where strong afternoon sunlight enters the home.
A properly maintained system can operate more efficiently.
APS recommends servicing an AC system yearly to help maintain efficient operation.
Check your ductwork
Leaky or poorly insulated ducts can waste conditioned air before it reaches living spaces. The Department of Energy has noted that duct systems can account for significant conditioned-air losses when poorly sealed.
When Should You Call an AC Professional?
Contact an HVAC professional if:
Your AC can't reach the thermostat setting.
Your system runs constantly without adequately cooling the home.
Some rooms are significantly hotter than others.
Your AC is blowing warm air.
Your system is repeatedly freezing.
Your outdoor unit isn't operating properly.
You notice water leaking around the system.
Your energy costs suddenly increase without a clear explanation.
Your AC is making unusual noises.
These symptoms can indicate a problem that isn't going to be solved simply by changing the thermostat.
Frequently Asked Questions
What is the best AC temperature for a Phoenix home?
A practical starting point is 78–80°F when you're home. SRP recommends this range for Arizona summer energy savings.
What temperature should I set my AC when I'm away?
SRP recommends up to 85°F when you're away.
Is 72°F too cold for an AC in Phoenix?
72°F is a much lower thermostat setting than the 78–80°F range recommended by SRP for energy savings. A lower setting can increase cooling demand and operating costs.
Why can't my AC maintain 78°F?
Possible causes include restricted airflow, dirty filters, refrigerant problems, duct issues, inadequate insulation, equipment problems, or an improperly sized system.
Does lowering the thermostat cool my house faster?
Not necessarily. Setting a much lower target doesn't automatically make the AC remove heat faster.
Should I turn my AC completely off when I leave?
For extended absences, raising the thermostat can reduce unnecessary cooling. APS says homeowners leaving for longer than a day can set the thermostat as high as 85°F and cool the home before returning.
Final Takeaway
There isn't one thermostat setting that is perfect for every Phoenix household.
However, 78–80°F while you're home is a practical starting point, and raising the thermostat when you're away can reduce unnecessary cooling. SRP currently recommends 78–80°F at home and up to 85°F away.
If your AC struggles to maintain a reasonable temperature even when properly set, the thermostat may not be the problem.
Your system may need AC repair, maintenance, airflow correction, or replacement.
Is Your AC Struggling to Keep Your Phoenix Home Cool?
If your thermostat is set to a reasonable temperature but your home still isn't staying comfortable, it may be time to have your AC system inspected.
Elite AC & Heating provides professional HVAC services for homeowners in Phoenix and surrounding areas.
Need AC service?
Contact Elite AC & Heating today to schedule an appointment.
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