Q&A
Heat pumps can rack up expensive energy bills during winter if not configured properly. Industry experts recommend adjusting two key settings to maximize efficiency and reduce costs when temperatures drop. These simple changes can deliver significant savings without sacrificing comfort during the coldest months.
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Tim WallaceCold Climate Heat Pump Specialist | HVAC Solutions Manager · Arctic Heat PumpsHi,
Am Tim Wallace, Cold Climate Heat Pump Specialist in Arctic Heat Pumps
For cold-climate heat pumps (especially modern EVI/DC inverter models that perform well down to -20degF or lower), the best thermostat strategy during deep freezes prioritizes minimizing auxiliary/backup heat while balancing comfort and energy costs.
Core Principle
Cold-climate heat pumps are highly efficient at maintaining steady temperatures but recover slowly from large drops. Aggressive setbacks often trigger expensive electric resistance auxiliary heat (AUX) during morning recovery, wiping out (or reversing) savings.
My Most Effective Strategy (Real-World Savings)
In my installations across Zone 5-7 climates, clients see the biggest bill reductions with:
No setback or very minimal (1-3degF max) during extreme cold (<20degF outdoors).
Keep a constant setpoint (e.g., 68-70degF daytime, same or 1degF lower at night). This lets the inverter modulate low and steady—where COP is highest—without ever hitting AUX.
Gradual recovery if you must setback for sleep comfort.
Use a smart thermostat (ecobee, Nest, or Honeywell) with "adaptive/smart recovery." Example schedule:
Drop to 67degF at 10 PM (from 69degF).
Start pre-recovery at ~4 AM to hit 69degF by 7 AM without spiking demand.
This avoids AUX in most cases and saves ~5-10% vs. constant if recovery aligns with milder morning temps.
Key Tweak That Made the Biggest Difference
Raising the auxiliary heat lockout temperature as high as comfort allows (e.g., 30-35degF outdoors).
Many defaults are conservative (20-25degF), forcing AUX too early. On true cold-climate units (Mitsubishi Hyper-Heat, Daikin Aurora, etc.), I've set lockouts to 35degF+ with an outdoor sensor—relying solely on the heat pump down to 0degF or below. One client in Minnesota cut AUX runtime by 80% and saved ~$250 over a polar vortex week.
Why This Beats Deep Setbacks
Deep drops (5degF+) force full-capacity recovery in the coldest hours - lower COP + AUX engagement - higher bills. NREL and DOE studies show no-setback or minimal strategies often use 10-20% less energy in sub-zero stretches.
Regards,
Tim Wallace
https://www.arcticheatpumps.com/
Climate Heat Pump Specialist
Heat pump setbacks work best when tied to real absences, not guesses. Use a schedule that matches work hours, school runs, or regular errands. Geofencing and occupancy sensors can switch to away mode only when the home is truly empty.
This avoids wasteful recoveries caused by short trips or quick returns. For travel or holidays, a vacation mode can hold a deeper setback until the return time. Map your routine and set an away setback that only engages during confirmed absences today.
On mild winter days, small setbacks can save energy without stressing the system. Dropping the setpoint by one to three degrees reduces run time while keeping comfort close. Recovery is gentle because the outdoor air is not frigid.
This helps the heat pump avoid using backup electric heat during warm-up. A weather-aware thermostat or simple check of the forecast can guide how small the setback should be. Watch the next mild spell and try a shallow setback to see the savings.
Longer setback periods often save more than deeper drops. A moderate lower setpoint kept for several hours lets the compressor run in steady, efficient cycles. Short, deep dips can trigger frequent starts and may invite backup heat at recovery.
Holding a mild setback across the full workday or overnight builds consistent savings. Tracking energy use over several weeks can reveal which timing pattern saves more in a given home. Set a modest setback and extend its hours to test this approach.
Zoning keeps heat where people are and lowers it where rooms sit empty. Smart thermostats, room sensors, or ductless heads can target occupied spaces. Doors closed to guest rooms or storage areas reduce the volume that must be heated.
Keep a safe minimum in cold-prone spots to protect pipes and finishes. Sealing drafts in unused rooms makes the lower setpoint even more effective. Choose key zones to heat now and lower the rest for steady savings.
Time-of-use rates reward heating before prices spike and easing back during peaks. Warming the home a bit early stores heat in walls and furniture. During the peak window, a slightly lower setpoint lets the space coast with small losses.
This limits run time when electricity is most costly and often most carbon heavy. Many smart thermostats can automate this with a price schedule or utility signals. Check your rate plan and set a preheat-and-coast routine before the next peak period.
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