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Thermostat Settings

Why heat pumps differ from furnaces

A furnace can recover from a 7°F setback quickly with hot air. A heat pump delivers warm air at a gentler rate, and many thermostats call for electric backup if the temperature lags. Backup strips at a COP of 1 cost more than the heat pump, so a deep setback can cost more than it saves.

Recommended approach

• Choose a comfortable temperature and keep it steady, or use small setbacks.
• Use a thermostat designed for heat pumps, with adaptive recovery that starts early.
• Ask the installer to set an outdoor temperature lockout for auxiliary heat.
• In dual-fuel systems, set the switchover temperature near the cost break-even.
• In summer, moderate setups and fan "Auto" help humidity control.

Mini-split controls

Mini-split remotes measure temperature at the head, which can read warmer than where you sit. Wall-mounted remote sensors or wired thermostats can improve comfort. Avoid switching heads off and on daily in cold weather; reheating a cold room takes longer.

Worked example

Figures below are illustrative examples (2026-10-29), not quotes or guarantees.

A home sets back from 70°F to 62°F overnight. In the morning the thermostat calls for 8°F of recovery and brings on 10 kW of strips for 40 minutes, using about 6.7 kWh, about $1.00 at $0.15/kWh. A 2°F setback may let the heat pump recover alone.

Setting auxiliary heat lockouts

Many heat pump thermostats include an auxiliary heat lockout, an outdoor temperature above which backup strips are not allowed to run. Installers often set it somewhere between 25 and 40°F, depending on how well the heat pump performs in cold weather and how the house is built. A lower lockout saves money but may leave the house slow to recover. A compressor lockout does the opposite in dual-fuel systems, stopping the heat pump below a chosen temperature and handing over to the furnace. These settings usually sit in an installer menu; ask your contractor to explain and record them.

Adaptive recovery and smart features

Adaptive or smart recovery learns how long the house takes to warm and starts early so the target is reached at the scheduled time without backup heat. Some smart thermostats include outdoor-temperature data and adjust strategy. Check that your thermostat is compatible with your heat pump's wiring and that it can control variable-speed equipment properly; some communicating systems work best with the manufacturer's own control.

Summer settings

For cooling, a steady setting with moderate increases when you are away works well. A 3 to 4°F setup during the day is common. Keep the fan on Auto in humid climates so moisture removed by the coil drains away instead of re-evaporating. If rooms feel clammy, ask whether your system has a dehumidification mode or reduced airflow setting.

Shoulder seasons

In spring and fall, a heat pump may switch between heating and cooling in a single day. An "Auto" mode with a dead band of a few degrees between heat and cool set points prevents rapid switching. A dead band of 3 to 4°F is typical.

Zoned and multi-head systems

With several mini-split heads, set each room based on use. Bedrooms can run slightly cooler at night. Avoid fighting between heads in open areas, such as one heating and another cooling. Some systems let you lock modes to prevent this.

Time-of-use rates

If your utility charges more at peak hours, you can pre-heat or pre-cool the house slightly before the peak and allow a small drift during it. A well-insulated house holds temperature longer, making this more effective. Check rates on your bill.

Common mistakes

• Using Emergency Heat on cold days, which disables the heat pump.
• Setting deep nighttime setbacks that trigger strips each morning.
• Switching between Heat and Off daily in cold weather.
• Installing an incompatible thermostat.
• Turning fan to On permanently in humid summers.

Checking your settings

Watch the thermostat display for "Aux" during normal mornings. If it appears often, reduce your setback or ask your installer to review lockouts. Compare monthly bills with weather to spot changes. See backup heat strips and heat pump not heating.

Setting up a new thermostat

When a heat pump is installed, the installer should configure the thermostat for heat pump mode, set the reversing valve signal correctly, enable staging for backup heat, and set the compressor and auxiliary lockout temperatures. A thermostat left in furnace mode can bring on strips too often. Ask for a printed record of the settings.

Humidity and comfort

In winter, very dry air can make a steady setpoint feel cooler than it is. A humidifier or simply keeping the house slightly warmer can help. In summer, setting the fan to Auto rather than On lets the coil remove more moisture.

Vacation settings

For trips longer than a few days, a deeper setback saves energy because there is no daily recovery. Keep the house warm enough to protect pipes, and schedule the return to normal temperature a day early so the heat pump can recover slowly without strips. Smart thermostats can do this remotely.

Emergency heat explained

Emergency heat turns off the compressor and runs only the strips. It is meant for outdoor unit failures, not cold days, because it costs much more to run. If you use it, call for service promptly and switch back once repaired.

Shared households

Agree on a steady setpoint; frequent manual changes trigger backup heat.

When to leave the fan on Auto

Auto lets the fan run with the heating or cooling call and stop afterward, which is usually the quietest and most efficient choice. Continuous On can mix air between rooms and dry a basement in humid weather, but it also moves unconditioned air through leaky ducts and can raise bills. Start with Auto unless a contractor recommends otherwise for your layout.

FAQ

Should I use Emergency Heat when cold?

No, only when the heat pump fails.

Does fan On help?

It evens temperatures but can raise humidity in summer.

What setpoint is cheapest?

The lowest comfortable steady setpoint.

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