Short answer: pick a comfortable temperature (around 68°F), leave it there, and raise it in small steps. Big setbacks can force the system to use electric backup heat, which costs about 2 to 5 times as much to run, according to Jackson EMC. The DOE also advises a moderate, steady setting for heat pumps in heating mode (energy.gov).
Know your heat sources
| Mode | What runs | Relative cost |
|---|---|---|
| Heat (normal) | Heat pump compressor | Lowest; can deliver up to 3 units of heat per unit of electricity |
| Aux heat | Heat pump plus electric strips (or furnace in dual-fuel) | Higher; kicks in automatically when needed |
| Emergency heat | Electric strips or furnace only | Highest; manual, for real emergencies |
Efficiency figure from DOE; cost range from Jackson EMC.
7 settings and habits that cut costs
- Hold a steady temperature. Around 68°F while you’re home, as Jackson EMC suggests.
- Small setbacks only: 2-3°F at night, if any, unless your thermostat is designed to recover without strip heat.
- Raise the setting in steps of 2°F or less in very cold weather, so the heat pump can keep up on its own.
- Use a heat pump-aware thermostat that can lock out aux heat above a chosen outdoor temperature. See smart thermostat savings.
- Leave “emergency heat” off unless the outdoor unit has failed.
- Use “auto” fan or a low continuous fan as your installer recommends; avoid high fan speeds that blow lukewarm air.
- Keep vents and returns open and unblocked. Closing vents can reduce airflow and efficiency.
Defrost cycles are normal
In cold, damp weather the outdoor coil frosts over. The system briefly reverses to melt it, and you may see steam rising from the outdoor unit. The DOE notes that demand-defrost controls keep these cycles to a minimum. If the unit is encased in ice for hours, call a technician.
Maintenance that matters in winter
- Check filters monthly in heavy use; dirty filters reduce airflow.
- Keep the outdoor unit clear of snow, ice and leaves, with at least a couple of feet of open space around it.
- Make sure it sits above snow level on a stand or bracket.
- Annual service to check refrigerant charge and airflow.
Is it working right?
Warning signs: aux heat running for hours on mild days, a big jump in your bill, rooms that never reach the setpoint, or a unit that’s iced solid. A system that relies on strips at 35°F is probably undersized, low on refrigerant or poorly configured. For how heat pumps perform in deep cold, see do heat pumps work in cold climates.
FAQ
Should I turn it off when I leave for the day? No. Use a small setback or none; reheating a cold house may trigger strip heat.
Why does the air feel cooler than a furnace? Heat pumps deliver air at a lower temperature over longer run times. Rooms stay evenly warm even though the air at the vent feels less hot.