The balance point is the outdoor temperature at which your heat pump’s heating capacity exactly matches the rate at which your home loses heat. Below the balance point, the heat pump can’t keep up on its own and auxiliary heat is needed. Above it, the heat pump handles everything.
Every home has a different balance point, depending on insulation, window area, air sealing, and the size of the heat pump. For most homes in the US, the balance point falls somewhere between 25°F and 40°F.
Why it matters for your thermostat settings
Most smart thermostats have an aux lockout or balance point setting that tells the system: “below this outdoor temperature, allow auxiliary heat to supplement.” Getting this right has a direct effect on heating costs.
Set the balance point too high (say, 45°F) and aux heat runs on mild days when the heat pump alone could handle the load. You’re using expensive resistance heat when you don’t need to.
Set it too low (say, 15°F) and the heat pump tries to keep up below its capability. The indoor temperature falls behind the setpoint, and the home is cold even though the system is running.
The correct balance point matches how your actual system performs in your actual climate.
How to find your balance point
The simplest method is observation:
- On a cold day, check the outdoor temperature and note whether the heat pump keeps up with the setpoint without aux heat coming on
- If aux heat runs consistently above 35°F, the balance point may need to be lowered
- If the house can’t keep up at 30°F without aux running, the balance point is working correctly
For a more rigorous approach, an HVAC tech can calculate your home’s heat loss at design conditions and your heat pump’s capacity curve, giving you a precise balance point.
Thermostat settings for balance point
Each major thermostat brand exposes this differently:
ecobee: “Aux Heat Max Outdoor Temp” (under Installation Settings → Thresholds). Set to your balance point. Below this temperature, aux heat can run. Above it, heat pump only.
Nest: Heat Pump Balance mode sets a preset balance point strategy (Max Savings aggressively delays aux, other modes are more liberal). Not a direct temperature entry, but Nest learns and adjusts based on how your system performs.
Honeywell T10 Pro: ISU 3090 sets the aux heat balance point in degrees. Also has ISU 3120 (compressor low-ambient lockout) for the low end.
For step-by-step settings on each thermostat, see Best Thermostat for a Heat Pump.
Balance point vs. compressor lockout
These are two different settings, often confused:
Balance point (aux lockout temperature): the outdoor temperature above which aux heat is prevented. The heat pump operates alone above this temperature.
Compressor lockout (low-ambient cutoff): the outdoor temperature below which the compressor is prevented from running — usually because low temperatures reduce refrigerant pressure enough that the compressor can’t operate safely. Most heat pumps have a built-in compressor lockout around 0–5°F. Standard heat pumps shouldn’t run compressors below this range; cold-climate units extend this to -13°F or lower.
Below the compressor lockout, the system runs on aux heat only (emergency heat effectively, but automatically).
| Setting | What it controls | Typical range |
|---|---|---|
| Balance point (aux lockout) | Outdoor temp above which aux heat is blocked | 25–40°F |
| Compressor lockout | Outdoor temp below which the compressor stops running | 0–5°F standard, -13°F or lower on cold-climate units |
Heat pump capacity ratings used to calculate a balance point come from AHRI-certified performance data (the same certification that produces the SEER2/HSPF2 numbers on the spec sheet) — a manufacturer’s published capacity-at-temperature curve is the input a technician actually uses to calculate your specific balance point, not a generic estimate.
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FAQ
What balance point temperature should I set? Most homes in moderate climates land in the 30–40°F range. Start at 35°F, observe whether aux heat runs excessively above that temperature, and adjust. A lower setting (25–30°F) works well for well-insulated homes or larger heat pumps.
My heat pump has been running for years. Does the balance point change? Yes, over time. As homes age, air sealing degrades, insulation settles, and the heat pump’s capacity decreases. A balance point that worked well at installation may need adjustment after 5–10 years.
Is the balance point the same as the auxiliary heat lockout? For most smart thermostats, yes — the aux heat lockout setting controls when aux is allowed to run based on outdoor temperature, which is functionally the balance point setting.
Does a higher balance point waste money? Yes, if it’s set higher than your actual balance point. Running electric resistance heat (aux) is 2–3x more expensive than running the heat pump to produce the same amount of heat. Minimizing unnecessary aux heat use is one of the highest-ROI thermostat adjustments for a heat pump home.
