Should You Turn the Thermostat Up When You Leave the House in Arizona?
Yes, you should turn the thermostat up when you leave the house in Arizona, but only by a few degrees, not ten or fifteen. A small setback of about four to seven degrees for eight hours or more saves energy without forcing your system to run flat out when you get home. Push it further than that in a Phoenix summer and you give most of the savings right back.
Why a small setback works and a big one does not
Your house gains heat from the outside all day long. The hotter it is inside, the slower that heat moves in, which is why a warmer empty house costs less to hold. That part is true. The catch is the recovery. A home that has baked at 88 degrees all afternoon has hot drywall, hot furniture and hot attic air over every ceiling, and your air conditioner has to pull all of that heat back out. In July, that can take hours at full tilt.
With a four to seven degree setback, the house never gets that soaked, so recovery is quick and the savings are real. Plenty of Glendale and Peoria customers turn a 78 degree house up to 90 while they work and then wonder why the bill barely moved.
Heat pumps are a different animal
If you have a heat pump, be careful with big setbacks in the heating months. Most heat pumps have backup electric strip heat that kicks on when the thermostat asks for a big jump all at once. Strip heat is the most expensive heat in the house. Ask for a three degree recovery and the compressor handles it quietly. Ask for eight degrees on a cold January morning and you may run strips for an hour. Our heat pump repair crews see this all winter.
For heat pumps, two to three degrees of winter setback, with a slow ramp so the strips stay off.
A real example from a Glendale house
A couple in Glendale called us last fall about heating repair in Glendale because their heat pump "never shut off in the morning." The system was fine. They were setting it to 62 overnight and 72 at six a.m., a ten degree jump, and the strip heat ran every morning to catch up. We changed the schedule to 67 overnight with a slow ramp starting at five, and the morning run time dropped by more than half. No parts, no repair, just a smarter setback.
What the thermostat itself has to do with it
A basic manual thermostat cannot ramp. It sees a big gap and calls for everything at once. A programmable or smart thermostat starts early and climbs a degree at a time, which is the whole trick. If your thermostat drifts, reads wrong, or loses its schedule, the plan falls apart. That is where our thermostat repair and replacement service comes in. We wire it, keep it off sunny walls and away from supply vents, and set the schedule with you. If it is acting up in other ways, our earlier post on why your thermostat is not working in Arizona covers the usual causes.
When you should not set it back at all
Some homes should leave the thermostat alone. If someone is home most of the day, there is no empty-house window to save in. If you have pets, medications, or a piano that does not like 88 degrees, hold the line. Homes with thin insulation or a lot of west-facing glass soak up heat so fast that a big setback turns into a long recovery. And if you are only gone three or four hours, the savings are not worth a sweaty return. Setback is a tool, not a rule.
Rules of thumb before you turn the thermostat up when you leave the house
• Summer, gone eight hours or more: set it four to seven degrees warmer than your normal setting.
• Winter with a heat pump: two to three degrees cooler, with a slow ramp back.
• Winter with a gas furnace: a bigger setback is fine, since the furnace has no strip heat to worry about.
• Vacation: keep it under about 85 in summer so the house, the fridge and the drywall do not cook.
• Use the schedule or a smart thermostat so the house recovers before you walk in.
Need a hand with your thermostat or your heating?
Western Sky Mechanical is family-owned with more than 40 years of experience across the Phoenix metro, ROC #366148. We give you a flat quote before work starts, back parts for a year and workmanship for two, and answer the phone 24/7 with no after-hours markup. Call 602-767-5341 and we will get your thermostat, heat pump or furnace set up the right way.
Frequently asked questions
How much should I turn the thermostat up when I leave the house in summer?
Four to seven degrees above your normal setting is the sweet spot for Arizona. Going higher than about 85 usually costs you more in recovery than it saves.
Does turning the AC off completely save more?
Not in Phoenix. An off house can hit the high 90s inside by late afternoon, and cooling it back down takes a long, hard run. Humidity and heat are also tough on electronics, flooring and pets.
Why does my heat pump run so long after I raise the thermostat?
A big jump makes the thermostat call for backup strip heat, which is slow and expensive. Keep winter setbacks small and let the system ramp up gradually. If it still runs constantly, have it checked.
Bottom line: turn the thermostat up when you leave the house, keep the change modest, and let a good thermostat do the ramping. That is how you save without paying it back at five o'clock.
Contact Western Sky Mechanical
Western Sky Mechanical
12509 W Sunnyside Dr.
El Mirage, AZ 85335
Phone: 602-767-5341
Stay connected with Western Sky Mechanical for HVAC tips, service updates, and helpful information for homeowners across the Phoenix area.
Follow Western Sky Mechanical Online:
Facebook| X| Instagram| YouTube
Worked with Western Sky Mechanical?
You might also like
