Electric heat pumps recently surpassed traditional central air conditioners in annual U.S. sales, reflecting growing demand (in part spurred by policymaking) for efficient, all-electric heating and cooling.

At their simplest, a heat pump is an air conditioner with one important upgrade: it can run in reverse. In the summer, it moves heat from inside the home to the outdoors, just like a conventional air conditioner.

In the winter, it reverses the process, extracting heat from the outdoor air and bringing it inside. Instead of buying equipment that sits idle for half the year, homeowners can ideally get year-round comfort from the same system.

But the equipment alone doesn't guarantee high performance. Thermostat settings, system commissioning, and homeowner education all have a significant impact on comfort, efficiency, and operating costs. A poorly configured heat pump, especially in extreme climate settings, can consume far more energy than necessary, even if the equipment itself is top-of-the-line.

Auxiliary Heat Backup

Heat pumps are remarkably efficient during mild winter temperatures, often delivering three to four units of heat for every unit of electricity they consume. But when outdoor temperatures plunge, the system may need a little help. That's where auxiliary heat comes in.

Auxiliary heat uses electric resistance elements (essentially oversized versions of the heating elements inside a toaster) to turn electricity into heat. While resistance heat is technically 100% efficient because every unit of electricity becomes heat, it's far less efficient than a heat pump, requiring three to four times more electricity to producing the same amount of heat.

For this reason, auxiliary heat should be viewed as a backup system, not the primary source of heating.

The challenge is that whether auxiliary heat operates efficiently depends almost entirely on how the thermostat is configured by the installing contractor. 

Different thermostat manufactures have different logic for deciding when to engage backup heat based on factors such as outdoor temperature, indoor temperature, and how long the heat pump has been running.

This logic is intended to turn on the auxiliary heat only if the indoor setpoint is not maintained. Unfortunately, these settings are often adjusted during installation.

One of the most common mistakes is locking out the heat pump at a specific outdoor temperature (typically between 35°F and 45°F). Many modern heat pumps can continue operating efficiently well below 15°F, so switching to resistance heat too early can dramatically increase a homeowner's utility bills and add strain to an already-stressed electric grid.

There's rarely a need to “lock out” the compressor altogether. If the home starts falling behind the thermostat setpoint, auxiliary heat can automatically provide additional support while allowing the heat pump to continue doing the heavy lifting.

Proper commissioning ensures homeowners get the efficiency they paid for while reducing unnecessary demand on the electric grid during peak winter conditions.
Educate Your Buyers

Homebuyer education regarding how heat pumps operate is also important to ensure peak performance. Some consumers may be confused why the “air conditioner” is running during the winter, or why the equipment runs significantly longer than a gas furnace to keep a home warm.

In fact, instead of cycling on and off, heat pumps typically run longer and deliver warm rather than truly hot air to maintain a more consistent indoor temperature.

Many thermostats also include an "Emergency Heat" mode, which disables the heat pump entirely and relies solely on electric resistance heat. If homeowners accidentally leave this mode enabled, they could unknowingly increase their heating costs by a factor of three or four.

Demystifying the Defrost Cycle

Another feature that often surprises homeowners is the defrost cycle. When operating in heating mode, the outdoor unit becomes cold enough for frost to form on the coil. Over time, that frost acts like insulation, reducing heat transfer and restricting airflow.

To combat this, the heat pump will temporarily reverse its cycle for a few minutes and run as an air conditioner, heating up the outdoor coils using energy from inside the home.

Occupants tend to not like to have the air conditioning on in the middle of winter, so the auxiliary heater is engaged to warm the cold air coming out of the indoor coil and prevent cold air being distributed to the house.

The defrost cycle is typically controlled by the outdoor unit and is based on a temperature sensor and a timer. The manufacturer defines a temperature threshold, typically around 32F. When the coil drops below this temperature, a defrost cycle will be engaged after the timer hits a set point. This is typically adjustable, and can vary from 1-4 hours.

Raising the Bar

If the auxiliary heater presents so many challenges, then why don’t we make the heat pump itself operate better at lower temperatures? That’s exactly what cold climate heat pumps do. They employ several strategies to maintain heating capacity when the mercury drops: 

• Use a variable speed motor and compressor to push more heat-transferring refrigerant through the system at low outdoor temps
• Feature larger outdoor coils for greater heat transfer surface area
• Employ an electronic expansion valve that does a better job of regulating refrigerant flow than the older analog type
• Use advanced refrigerant management techniques, such as enhanced vapor injection, to "turbocharge" compressor operation

Combined with ensuring that the thermostat is set-up and configured correctly, these technologies allow cold climate heat pumps to continue delivering efficient heating at temperatures that would challenge conventional systems.

Optimizing Value

Many new homes are now equipped with two-stage or variable-capacity heat pumps.

Unlike single-stage systems that always operate at full output, two-stage equipment can run at lower speeds when heating or cooling demand is lower.

The result is improved efficiency, more consistent temperatures, and potentially better humidity control during cooling season. However, builders only realize those benefits if the equipment is properly commissioned.

Recent field monitoring by IBACOS found that approximately 40% of two-stage heat pumps installed in one new community were never operating in both stages due to incorrect contractor installation and commissioning. In those cases, builders paid for premium equipment, but homeowners received little additional value.  

A thorough quality assurance process that verifies staging and thermostat operation before homeowner move-in is essential.

The Demand Response Factor

Heat pumps also create opportunities beyond energy efficiency. Many electric utilities now offer demand response programs that reward homeowners for allowing small thermostat adjustments during periods of peak electricity demand. These events typically last only a couple of hours and occur just a few times each year.

In exchange, homeowners may receive enrollment incentives and billing credits while helping utilities reduce stress on the electric grid. Participation is always voluntary, and homeowners can override any adjustment if they become uncomfortable.

The Bottom Line

Heat pumps have become one of the most important technologies in today's high-performance homes. But delivering on their promise requires proper installation, thoughtful thermostat configuration, quality commissioning, and homeowner education.

When these pieces come together, homeowners can enjoy lower energy bills, greater comfort, and confidence that their heat pump is performing exactly as it should.