When Do Electric Heating Elements Operate With a Heat Pump

Heat pumps are a primary heating source in many American homes, but electric heating elements often appear as a supplemental heat source. This article explains when electric heating elements operate with a heat pump, the control strategies that govern their use, and how homeowners can balance comfort, efficiency, and cost.

Mode	When Electric Elements Operate	Typical Purpose
Stage 1 (Heat Pump Only)	Normal operation above balance point	Most efficient heating
Stage 2 (Supplemental Elements)	When demand exceeds heat pump capacity	Maintain setpoint during cold snaps
Emergency Heat	Heat pump malfunction or manual selection	Backup heating using resistance elements
Defrost Cycle	Short, intermittent use during defrost	Protect outdoor unit and preserve performance

How A Heat Pump And Electric Elements Work Together

A heat pump moves heat from outdoors to indoors using a refrigerant cycle; it is efficient down to certain outdoor temperatures. Electric heating elements, often called resistance heat or strip heat, convert electrical energy directly to heat and provide immediate output without a refrigerant cycle.

When electric heating elements are used in conjunction with a heat pump, they serve as supplemental or backup heat. The heating system control determines when to activate those elements based on temperature, demand, and safety algorithms.

Types Of Electric Heating Elements In Heat Pump Systems

There are several common types of electric elements paired with heat pumps.

• Auxiliary (Aux) Heat: Automatically engages when the heat pump cannot meet thermostat demand during very cold conditions or rapid temperature recovery.
• Emergency Heat: Manually or automatically selected when the heat pump fails; runs continuously as the primary heat source until repaired.
• Supplemental/Stage 2 Heat: Works in staged systems where the thermostat adds resistance heat to maintain setpoint when the heat pump alone is insufficient.
• Defrost Heat: Short bursts during outdoor coil defrost cycles to prevent indoor temperature sag while the outdoor unit temporarily reverses to defrost.

Control Strategies That Determine Operation

The timing of electric element operation depends primarily on the system controls: thermostats, control boards, and sensor inputs. Common strategies include staged heating, auxiliary lockout, balance point management, and emergency heat modes.

Staged Heating

In multi-stage systems, the thermostat calls for heat in stages. Stage 1 typically runs the heat pump alone. If the heat pump cannot keep up, Stage 2 calls electric elements to assist. This prevents short cycling and reduces energy use while meeting comfort goals.

Auxiliary Lockout

Auxiliary lockout prevents electric elements from running until the outdoor temperature drops below a set threshold. This control favors the heat pump’s efficiency and only allows resistance heat when necessary, reducing operating cost.

Balance Point Management

The balance point is the outdoor temperature where the heat pump’s output equals the heat loss of the house. Below this balance point, the system relies partly or wholly on electric elements. Thermostats or control boards may use fixed balance points or adaptive algorithms based on load history.

Emergency Heat Mode

When the thermostat is set to emergency heat, the heat pump is disabled and electric heating elements run continuously. This is used during heat pump failure or when the outdoor unit is iced over and cannot operate effectively.

When Electric Elements Typically Turn On

Electric elements operate under predictable circumstances, determined by system configuration and external conditions.

• Cold Outdoor Temperatures: When the outdoor temperature drops below the heat pump’s effective range or the predefined balance point, auxiliary or supplemental elements engage.
• High Indoor Demand: Rapid recovery after a setback (large temperature difference between setpoint and current indoor temp) can trigger elements to help the heat pump meet setpoint faster.
• Defrost Cycles: During outdoor coil defrost, brief indoor resistance heating prevents comfort loss while the heat pump temporarily stops heating.
• Heat Pump Faults or Malfunctions: If the compressor or reversing valve fails, emergency heat may be enabled automatically or by user selection.
• Thermostat Settings: Certain thermostats with tighter deadbands or aggressive setpoint control may call for auxiliary heat more frequently.

Impact On Efficiency And Energy Costs

Electric resistance heat is significantly less efficient and more expensive than a properly operating heat pump. Resistance heat has a COP (coefficient of performance) of roughly 1.0, while heat pumps often operate at COPs of 2.0–4.0 or higher depending on conditions.

Because of this, control strategies aim to minimize electric element runtime. Auxiliary lockout, proper thermostat calibration, and system sizing help ensure electric elements only run when necessary.

Thermostat Role And Settings

The thermostat is the main interface that decides when supplemental heat engages. Modern thermostats and heat pump thermostats include logic for stage control, balance point, and lockout thresholds.

Important thermostat settings include:

• Heat Pump Type/Stages: Correctly configure single-stage vs multi-stage.
• Auxiliary Lockout Temperature: Set the temperature below which aux heat is allowed.
• Recovery/Setback Parameters: Adjust to avoid unnecessary auxiliary activation during short recovery periods.

Practical Tips For Homeowners

To minimize unnecessary use of electric heating elements, homeowners can take several practical steps.

• Use A Heat Pump-Specific Thermostat: Ensures proper staging and lockout logic.
• Avoid Manual Emergency Heat Selection: Do not use emergency heat except when the heat pump is actually malfunctioning; running emergency heat increases electric bills.
• Set Reasonable Setbacks: Large overnight setbacks can trigger auxiliary heat during morning recovery; smaller setbacks reduce supplemental runtime.
• Maintain The System: Regular maintenance keeps the heat pump efficient and delays or reduces the need for electric elements.
• Consider Supplemental Heat Sources: Zoned thermostats, mini-splits, or gas furnaces can reduce reliance on electric resistance heat in cold climates.

Cost Considerations And Sizing

Electric elements are typically sized to provide full backup capacity, which can be expensive to operate if used often. Proper system sizing of the heat pump and house insulation reduces the likelihood of frequent electric element use.

When evaluating upgrades, compare operating cost of auxiliary electric heat versus alternatives such as a higher-capacity heat pump, cold-climate heat pump, or a hybrid system pairing heat pump with gas furnace.

Cold Climate Behavior And Cold-Climate Heat Pumps

Traditional heat pumps lose efficiency at low temperatures, leading to more electric element use in sustained cold periods. Cold-climate heat pumps extend effective operation to lower temperatures and reduce the need for resistance backup.

Systems in very cold regions often use a hybrid approach (heat pump plus fossil-fuel furnace) to minimize electric resistance usage during prolonged subfreezing conditions.

Defrost Mode And Short-Term Electric Use

During a defrost cycle, the outdoor unit temporarily reverses to melt frost on the outdoor coil. That momentary reverse causes indoor air to cool slightly, so the control may energize electric elements for a short period to maintain indoor comfort.

Defrost-related element use is brief and normal. Persistent element activation during defrost could indicate defrost control problems or refrigerant issues.

Troubleshooting Excessive Electric Element Operation

If electric elements run frequently, investigate common causes to restore efficiency.

• Incorrect thermostat wiring or configuration causing early stage calls.
• Faulty sensors or control board sending false signals for aux heat.
• Undersized heat pump or poorly insulated home increasing heat loss.
• Heat pump malfunctions reducing output, triggering emergency heat.

Professional diagnostics can identify wiring, control, or equipment faults that lead to unnecessary electric heat use.

Regulatory And Incentive Considerations

Energy programs and incentives often prioritize heat pump performance and electrification. Upgrading to more efficient heat pumps or cold-climate models can reduce reliance on electric resistance heat and may qualify for rebates.

Homeowners should check local utility and federal programs for incentives that lower upgrade costs and improve long-term operating expenses.

Frequently Asked Questions

Do Electric Elements Turn On As Soon As The Thermostat Calls For Heat?

Not necessarily. The thermostat and control logic usually call the heat pump first. Electric elements typically engage only after the heat pump fails to meet demand, when outdoor temperatures are below the balance point, or during emergency heat selection.

Is Emergency Heat The Same As Auxiliary Heat?

No. Emergency heat disables the heat pump and uses electric elements as the primary heat source. Auxiliary heat runs only when needed in parallel with the heat pump to supplement output.

Can A Thermostat Prevent Electric Elements From Running?

Yes. Thermostats with auxiliary lockout and proper staging can prevent unnecessary use by delaying or disallowing resistance heat until conditions require it.

How Can A Homeowner Reduce Electric Element Use?

Use a heat pump–compatible thermostat, maintain the heat pump, improve insulation and air sealing, and consider upgrading to a cold-climate heat pump or hybrid system.

Key Takeaways

Electric heating elements operate with a heat pump primarily when the heat pump cannot meet demand due to low outdoor temperatures, rapid recovery needs, defrost cycles, or system faults. Proper thermostat configuration, system sizing, and maintenance minimize electric element runtime while preserving comfort and limiting operating costs.