How Does Emergency Heat Work?: 2025 Explanation

Understanding the Basics of a Heat Pump and Emergency Heating

To understand how emergency heating works, you’ll need to know how a heat pump works and why emergency or auxiliary heating are necessary.

A heat pump works by extracting heat from the outside air (even in winter) and transferring it indoors. In cooling mode, the process is reversed, removing heat from inside your home to the outside. This dual functionality makes heat pumps highly efficient and environmentally friendly.

In the heating mode, hot refrigerant gas flows from the compressor to the evaporator heat exchanger inside the home to heat air circulated through the system and home by the blower fan. The refrigerant then moves through the outside condenser unit to draw heat from outside air. Next, the refrigerant flows back to the compressor to get heated up and pumped back through the evaporator to heat inside air.

However, as outdoor temperatures plummet, the heat pump’s ability to heat your home using the sealed refrigerant system diminishes. To compensate, heat pumps are equipped with an auxiliary (or supplemental) heat sources, such as electric heating element or gas furnace burner.

Auxiliary Heating

When outside temperature drop below 30 degrees, you’ll first see auxiliary heating kick in on your heat pump. The electric heating element or auxiliary furnace burner will activate at the same time that the heat pump sealed system continues to heat the home.

Emergency Heating

When outside temperature drops to a point where the sealed system of the heat pump isn’t able to heat the home at all, the compressor and sealed system shuts down and all heating is provided by the backup electric heating element or auxiliary furnace component of the heating system. “Emergency Heat” will displayed on the thermostat when this happens.

In some systems, you can manually choose emergency heating. When you start up the heat pump and the inside air temperature is significantly lower than the set temperature, the heat pump system may automatically enable emergency heating or auxiliary heating to initially heat up your home.

When a malfunction of the sealed system in a heat pump occurs, the thermostat and control system will activate emergency heating to heat your home while you schedule heat pump repair and get the sealed system back online. If the thermostat or control doesn’t automatically activate emergency heating, you can activate emergency heating manually on many heat pump systems.

When Should You Use Emergency Heat?

Emergency heat is not meant for everyday use—it’s designed for specific scenarios. You should only activate emergency heating in these situations:

• Heat Pump Malfunction: If your heat pump stops working due to mechanical failure, emergency heat can maintain indoor comfort until repairs are made.
• Extremely Cold Weather: While most heat pumps are engineered to perform efficiently in moderately cold climates, some may struggle during extended periods of sub-freezing temperatures.
• Faster Recovery: In cases where the heat pump cannot heat your home quickly enough, emergency heat may help achieve desired temperatures more rapidly. After a lengthy power outage during cold weather, you may need to heat your home quickly. If you’ve been away and arrive home in cold weather, you may also need to use emergency heat to initially raise indoor temperatures quickly.

Drawbacks of Using Emergency Heat

While effective in emergencies, relying on emergency heat comes with certain downsides:

• Higher Energy Costs: Electric resistance heaters consume significantly more electricity than a heat pump, leading to higher utility bills.
• Increased Wear and Tear: Prolonged use of emergency heat can strain the auxiliary system, potentially leading to maintenance issues.
• Less Efficiency: Heat pumps are inherently more energy-efficient than emergency heat systems, so using this mode unnecessarily undermines the cost and energy savings of your setup.

How to Tell If Emergency Heat Is Needed

Most modern thermostats and heat pumps are equipped with sensors and controls to determine when auxiliary heat should engage. In most cases, the system will activate the backup heat source automatically when necessary. However, you should manually switch to emergency heat if:

• The outdoor unit is visibly damaged or frozen over.
• Your heat pump is not providing adequate heat, and temperatures inside your home are dropping rapidly. Schedule heat pump repair service immediately to fix the sealed system failure.
• You need to initially heat up your home after a power outage or when returning home to a cold house after a trip.

Tips for Proper Emergency Heat Usage

• Monitor Energy Costs: Only use emergency heat temporarily, as it is more expensive to operate than your heat pump.
• Schedule Heat Pump Maintenance: Regular heat pump maintenance by an HVAC technician ensures it remains efficient even during cold weather, reducing the need for emergency heat.
• Invest in a Smart Thermostat: A smart thermostat can efficiently automate the process of switching between heat pump and auxiliary heat, optimizing comfort and energy usage.

Emergency heat is a valuable feature that ensures your home stays warm during equipment failures or extremely cold weather.

While it serves an important purpose, it should be used sparingly to avoid high energy costs and unnecessary wear on your system. Understanding how and when to use emergency heat will keep your home comfortable and your HVAC system running efficiently.

By maintaining your heat pump and using emergency heat wisely, you can stay cozy all winter long without breaking the bank.