Thermostat Settings That Actually Save Money in an Arizona Winter
Deep setbacks that work with a gas furnace can cost you money with a heat pump. Here is how to set each one for a Valley winter.
In an Arizona winter, set a gas furnace to about 68°F when home and 62°F when away or asleep. With a heat pump, use much smaller setbacks — no more than two or three degrees — because recovering from a deep setback triggers expensive auxiliary strip heat. Never use emergency heat as a comfort setting.
The rule that changes depending on your equipment
Almost every energy-saving article repeats the same advice: set it back at night and while you are away. That advice is correct for a gas furnace and actively wrong for a heat pump, and nobody ever mentions the distinction.
A furnace produces heat at the same rate regardless of how far the house has drifted. Recovering ten degrees simply takes longer. A heat pump is different: when the thermostat sees a large gap between the current temperature and the setpoint, it engages auxiliary electric strip heat to catch up faster — and strip heat costs roughly three times as much to run.
So the deep setback saves you money for eight hours and then hands it all back, with interest, during a forty-minute recovery on strip heat.
Settings for a gas furnace
Straightforward. Larger setbacks genuinely save money.
- Home and awake: 68°F is the standard recommendation and most people find it comfortable with a sweater.
- Asleep: 62 to 65°F. Most people sleep better cooler anyway.
- Away: 60 to 62°F. Do not go below 55°F if there is any plumbing in an exterior wall or an unconditioned space.
- Recovery: schedule the setpoint to rise 30 to 45 minutes before you need the house warm.
Settings for a heat pump
Different logic entirely. Think "hold steady" rather than "set back."
- Home: 68 to 70°F.
- Away or asleep: no more than 2 to 3 degrees lower. A heat pump is most efficient holding a steady temperature.
- Use a heat-pump-aware thermostat. Better models include adaptive recovery that ramps the setpoint gradually to avoid triggering strip heat.
- Set the auxiliary heat lockout. This is the setting that matters most, and it is frequently never configured.
Emergency heat is not a comfort setting
EM HEAT or EMERGENCY HEAT bypasses the heat pump completely and runs on electric resistance only. It exists for the case where the heat pump has failed and you need heat tonight.
People switch to it because the house is not warming fast enough, forget about it, and get a startling bill. If you ever need it, treat it as a signal to call for service rather than a setting to leave engaged.
What actually moves the winter bill
Thermostat strategy is worth real money, but it is not the largest lever in most Valley homes. Duct leakage in an unconditioned attic, an unset auxiliary lockout, and a filter that has not been changed since summer typically cost more than a few degrees of setback ever saves.
If your heating bill jumped this year without a rate change, look at those three before you start rationing degrees.
Frequently asked
What temperature should I set my thermostat in winter in Phoenix?
About 68°F when home is the standard recommendation. With a gas furnace you can set back to the low 60s when away or asleep. With a heat pump, keep setbacks to two or three degrees, because deep setbacks trigger expensive auxiliary strip heat during recovery.
Is it cheaper to leave the heat at one temperature?
With a heat pump, essentially yes — holding a steady temperature avoids strip heat. With a gas furnace, no: setting back while away genuinely saves, because the furnace produces heat at the same cost per unit regardless of the gap.
Why did my electric bill spike after switching to a heat pump?
The most common reason is auxiliary strip heat running when it should not. Check the auxiliary heat lockout setting, confirm the thermostat is configured for heat pump operation rather than conventional, and verify the system is not stuck in emergency heat.