Heat Pump Thermostat Settings for Winter: Setback, Auxiliary Heat and Savings
For most heat pumps, the best winter thermostat setting is a steady one: pick the lowest temperature you are comfortable with, leave it there, and avoid big overnight or away-from-home setbacks unless you have a smart or programmable thermostat designed for heat pumps. Large, sudden setbacks can make the system call for its backup electric resistance heat (often labelled "aux" or "auxiliary heat") when it warms back up, and that backup heat costs more to run than the heat pump itself. This guide explains why heat pumps behave differently from furnaces, how to handle setbacks, what the auxiliary and emergency heat settings mean, and when it is worth calling a technician.
Why heat pumps need a different thermostat strategy
With a gas or oil furnace, the long-standing advice from the U.S. Department of Energy is that turning the thermostat back 7 to 10°F for 8 hours a day can save up to 10% a year on heating and cooling. A furnace can recover from a deep setback quickly, so lowering the temperature while you sleep or work simply means it burns less fuel during those hours.
A heat pump works differently. It moves heat rather than creating it, and it is most efficient when it runs steadily at moderate output. When the thermostat asks for a large jump in temperature, many systems decide the heat pump alone will not catch up fast enough and bring on backup electric resistance heat. The Department of Energy's Energy Saver guidance warns against setting back a heat pump manually if doing so causes the backup electric resistance heating to come on, and recommends using a smart or programmable thermostat designed for heat pumps if you want to set back at all.
NYSERDA, New York's energy agency, puts it plainly in its air-source heat pump operating tips: lowering the setpoint during unoccupied hours, or sudden temperature changes of 3°F or more, could trigger the heat pump to run in an inefficient catch-up mode and increase costs. The Northeast Energy Efficiency Partnerships (NEEP) consumer guide makes the same point for cold-climate heat pumps, noting that deep setbacks may cost you energy and money, and describing "set it and forget it" as an effective approach.
A sensible starting point for winter settings
There is no single correct number for every home, because comfort, insulation and the system itself all vary. The following approach reflects the guidance from DOE, NYSERDA and NEEP:
- Choose your comfort temperature and hold it. Start at the lowest setting that feels comfortable for your household. Older DOE materials have long used 68°F as a reference point for winter daytime comfort, but what matters most with a heat pump is consistency, not a specific number.
- Use "Heat" mode rather than "Auto". NYSERDA recommends choosing Heat or Cool rather than Auto, so the system is not switching between modes on mild days.
- Keep any setback small. If you like a cooler bedroom at night, a modest drop of a degree or two is far less likely to trigger backup heat than a large one. NYSERDA suggests raising the setting slowly, only a few degrees at a time, in the morning.
- Let a heat pump thermostat handle bigger setbacks. Thermostats designed for heat pumps can ramp the temperature up gradually so the backup heat is not needed. If yours is not designed for heat pumps, stick to a steady setting.
- Save long setbacks for long absences. A DOE-hosted homeowner guide for air-source heat pumps suggests reserving temperature setback for unoccupied periods longer than a day, and notes that switching the heat pump off while you are out can lead to inefficient operation when it restarts.
Auxiliary heat vs emergency heat: what the settings mean
Many heat pump thermostats show two related terms, and they are easy to confuse.
| Setting | What it is | When it runs |
|---|---|---|
| Auxiliary heat ("aux") | Electric resistance heat that supplements the heat pump | Automatically, when the heat pump needs help, for example in very cold weather or during recovery from a large setback |
| Emergency heat ("em heat") | Electric resistance heat used on its own, with the heat pump's compressor off | Only when you select it, typically if the outdoor unit has failed or is damaged |
Seeing "aux" light up occasionally on a very cold morning is normal. The DOE-hosted guide describes auxiliary electric resistance heat as costly and inefficient compared with the heat pump, which is why you want it to run as little as practical. A DOE quality installation document also notes that in extremely cold weather the thermostat brings on auxiliary or emergency heat automatically, and that the heat pump should not be switched to that mode by hand.
Emergency heat is a fallback, not an everyday setting. Leaving a thermostat on emergency heat turns your heat pump into an electric resistance heater, and your electric bill will show it. If you find yourself needing emergency heat, that is a sign the system needs attention.
Signs your settings, or your system, need a closer look
- Aux heat is on constantly. NYSERDA's guidance says that if auxiliary heat stays on all the time, or you see frequent use, you should have an HVAC professional check that the system is working properly.
- The home struggles to reach the setpoint on mild days. A heat pump should handle typical New Jersey and New York winter days without much help. Persistent shortfalls can point to a refrigerant, airflow or sizing issue.
- Your bill jumped after you started using setbacks. If a schedule you set up is triggering backup heat every morning, a steadier setting may cost less.
- You still have a furnace or boiler as backup. NYSERDA advises that if you keep an older heating system as backup, its thermostat should be set lower than the heat pump's so the heat pump does most of the work. If both systems are fighting over the same rooms, the older one may be running more than it should.
It also helps to know that the temperature at which backup heat comes on, and whether the compressor locks out in deep cold, are usually configured by the installer rather than the homeowner. If those settings are wrong for your home, a technician can review them.
What about ductless mini-splits?
Ductless mini-splits usually come with a handheld remote or wall controller for each indoor unit. The same general principle still applies: they run most efficiently at a steady setting. Rather than turning heads off when you leave a room, many homeowners find it works better to leave each zone at a moderate temperature and make small adjustments. Turning a head off in a cold room and then asking it to heat the room quickly from scratch is the mini-split version of a deep setback.
Honest trade-offs
Steady settings are not perfect for everyone. If your household is out for long hours every weekday, a steady temperature does mean heating an empty home. A smart thermostat designed for heat pumps can be a reasonable middle ground, because it can lower the temperature and then recover gradually. On the other hand, if your home is drafty or under-insulated, a steady setting may still not feel comfortable, and the real fix is often air sealing and insulation rather than thermostat changes. A thermostat cannot make up for a system that is undersized, poorly installed or overdue for maintenance.
Frequently asked questions
Should I turn my heat pump down at night?
Only a little. Small setbacks of a degree or two are usually fine. Larger drops can trigger expensive backup heat when the system warms the home back up, unless you use a thermostat designed for heat pumps that recovers gradually.
Is it cheaper to leave a heat pump on all the time?
In winter, generally yes. NYSERDA and NEEP both recommend a steady setting, because switching a heat pump off or making large setbacks can force it into an inefficient catch-up mode later.
What does "aux heat" mean on my thermostat?
It means the system is using electric resistance heat to supplement the heat pump. Occasional use in very cold weather is normal. If it runs constantly, have the system checked.
When should I use emergency heat?
Only if the outdoor heat pump unit has failed or is damaged and you are waiting for a repair. Emergency heat runs the resistance heat on its own and is much more expensive to operate.
Should my heat pump be on "Auto" mode in winter?
NYSERDA recommends using "Heat" mode in winter rather than "Auto", so the system does not switch between heating and cooling on mild days.
Do I need a special thermostat for a heat pump?
If you want to use setback schedules, yes. The Department of Energy recommends a smart or programmable thermostat designed for heat pumps, which can ramp temperatures up slowly to avoid bringing on backup heat.
Related services
- Heat pump installation
- Annual maintenance programs
- Ductless mini-split installation
Get your heat pump set up right for winter
Summit Air Heating & Cooling provides heat pump installation for homes across New Jersey and New York. If your heat pump leans on auxiliary heat more than you expect, your bills have climbed, or you are considering a new system and want straight answers on how it should be set up and controlled, book a free consultation. Contact us to schedule your consultation.
Guidance in this article is as of October 2026. Sources: U.S. Department of Energy Energy Saver Guide and home heating and cooling guidance; DOE-hosted homeowner guide for air-source heat pumps; NYSERDA Air Source Heat Pump Operating Tips and Best Practices for Your New Heat Pump fact sheets; NEEP "Getting the Most Out of Your Heat Pump" consumer guide. Always follow the instructions for your specific equipment and thermostat.
