What Is a Heat Strip for a Heat Pump and How It Works

A heat strip for a heat pump is an electric resistance element that provides supplemental or emergency heat when the heat pump cannot meet indoor heating demand. This article explains how heat strips work, when they activate, installation considerations, cost and efficiency impacts, troubleshooting tips, and best practices for homeowners and technicians. The goal is to clarify the role of a heat strip for a heat pump and help readers make informed decisions about operation and upgrades.

Topic	Quick Summary
Definition	Electric resistance elements used as backup for heat pumps
When It Runs	During very cold conditions, defrost cycles, or high-demand periods
Types	Single-stage, staged, and modulating heat strips
Impact On Bills	Significantly increases electricity use when active
Alternatives	Dual-fuel systems, larger heat pumps, geothermal, efficient ducting

How A Heat Strip For A Heat Pump Works

A heat strip is a series of electrically heated metal elements installed inside an air handler or furnace cabinet paired with a heat pump. When the thermostat calls for heat and the heat pump cannot produce sufficient warm air, the control system energizes the heat strip to produce immediate heat through resistance heating. The warm air is then circulated through the ductwork to maintain indoor temperature.

Heat strips are typically arranged in rows of coils or metal bars and wired in stages (for example, 5 kW, 10 kW, 15 kW). The system can energize one or multiple stages depending on the required output. The heat strip provides fast-response, predictable heat but is less energy efficient than the heat pump’s heat transfer process.

Why Heat Strips Are Used With Heat Pumps

Heat pumps extract heat from outdoor air and transfer it indoors. Their efficiency drops as outdoor temperatures fall, and at sufficiently low temperatures, they may not supply adequate heat. Heat strips act as a supplemental or emergency heat source to maintain comfort during these conditions. They also assist during indoor defrost cycles to reduce cold air drafts.

Common reasons heat strips run include: prolonged outdoor temperatures below the heat pump’s effective design range, high heating loads due to building heat loss, defrost cycles that temporarily stop heat pump output, and rapid thermostat setpoint increases. Heat strips ensure comfort continuity when the heat pump alone cannot keep up.

Types Of Heat Strips

Single-Stage Heat Strips

Single-stage heat strips switch fully on or off. They are simple and inexpensive but offer limited control over energy use and comfort fine-tuning. This design can cause abrupt changes in electric load and indoor temperature when engaged.

Staged Heat Strips

Staged heat strips energize in predefined increments (e.g., one, two, or three stages). Staging provides smoother temperature control and lower peak electrical demand than single-stage strips. It also allows the system to use only as much resistance heat as needed.

Modulating And Smart Heat Strips

Advanced systems include modulating or variable-output electric heat strips controlled by the heat pump system or a smart thermostat. These strips adjust output continuously to meet demand, improving comfort and reducing energy spikes. Integration with home energy management systems can further optimize usage during peak-rate pricing.

Sizing And Selection Considerations

Proper sizing of a heat strip is essential. An undersized heat strip may fail to maintain comfort during extreme cold, while an oversized strip can waste energy and create excessive electric demand. Sizing should consider the home’s heat loss, heat pump capacity, typical winter temperatures, and available electrical service.

Technicians usually calculate required supplemental capacity in kilowatts (kW) based on heating load calculations (Manual J). Common residential heat strip sizes range from 3 kW to 20 kW, often installed in multiple stages to match varied conditions. Electrical service capacity and breaker sizing must be verified before installation.

Installation And Safety Requirements

Installation of a heat strip for a heat pump should follow manufacturer instructions and local electrical codes. Proper mounting inside the air handler, secure wiring, and adequate breaker protection are crucial. The installer must confirm the air handler airflow matches the heat strip’s requirements to avoid overheating and safety risks.

Important safety elements include: using correct wire gauge, appropriate circuit breakers or fuses, high-limit safety switches to shut off heat if temperatures exceed safe thresholds, and proper grounding. Homeowners should never attempt DIY installation unless qualified and licensed.

Impact On Energy Use And Utility Bills

Heat strips are electric resistance heaters; they convert nearly 100% of electricity into heat. However, compared with heat pumps that deliver multiple units of heat for each unit of electricity (Coefficient Of Performance, COP, greater than 1), heat strips are far less efficient. Running heat strips substantially increases electricity consumption and heating costs.

As a rule of thumb, when a heat strip supplies most of the heat, energy use and bills can rise significantly, sometimes doubling heating costs depending on temperature and usage patterns. Staged or modulating use and managing thermostat settings can help reduce reliance on heat strips.

Alternatives To Relying On Heat Strips

Homeowners seeking to reduce heat strip usage can consider several alternatives and complementary upgrades. Options include upgrading to a cold-climate heat pump with better low-temperature performance, installing a dual-fuel system (heat pump plus gas furnace), improving home insulation and air sealing, and optimizing ductwork to reduce heat loss.

Other approaches include adding a heat pump with higher capacity, installing a ground-source (geothermal) heat pump, and integrating smart thermostats to limit heat strip activation. Reducing heat strip run-time improves comfort and lowers operational costs.

Control Strategies And Thermostat Settings

Thermostat strategies influence how and when a heat strip for a heat pump engages. Many heat pumps use a “balance point” or lockout strategy that allows heat strips to run only when outdoor temperature drops below a set threshold. Smart thermostats and heat pump controllers can minimize heat strip use by optimizing setpoint changes and leveraging predictive control.

Useful settings and strategies include using mild setback temperatures, gradual setpoint adjustments, enabling staged heat settings if available, and programming temperature thresholds for strip activation. Technicians can calibrate the control to engage heat strips only when necessary, balancing comfort and cost.

Troubleshooting Common Issues

Common issues with heat strips include failure to energize, frequent cycling, tripped breakers, unusual odors during initial run, and uneven heating. Troubleshooting begins with safety checks: ensure breakers are closed, fuses intact, and wiring connections secure. High-limit switches or thermal cutouts may have tripped and require inspection.

If strips do not energize while the thermostat calls for heat, technicians should verify control board signals, contactor operation, and thermostat wiring. Frequent trips or excessive cycling can indicate improper sizing, airflow restrictions, or thermostat misconfiguration. Always disconnect power before servicing internal components.

Cost Estimates And Maintenance

Costs for installing a heat strip for a heat pump vary by size, system compatibility, labor rates, and whether electrical upgrades are needed. Typical installed costs for a basic heat strip can range from a few hundred dollars to over a thousand dollars, excluding electrical service upgrades which can add significant expense.

Maintenance is minimal but important: annual inspection during HVAC tune-ups, checking electrical connections, testing safety cutouts, and ensuring clean air filters and proper airflow. Promptly addressing airflow or duct issues reduces the chance of heat strip overuse and premature component failure.

Codes, Incentives, And Regulations

Local electrical and mechanical codes govern installation of heat strips and associated wiring. In some areas, code requires specific breaker types, wire sizing, and protection devices. Installers must comply with National Electrical Code (NEC) provisions and local amendments.

Utility and federal incentives often focus on heat pump upgrades rather than electric resistance heat. Homeowners interested in reducing heat strip reliance may find rebates for cold-climate heat pumps, insulation improvements, or whole-home electrification programs. Checking local utility programs and state incentives is recommended.

When To Consider A Professional Assessment

Homeowners should seek a professional assessment if heat strips are running frequently, energy bills spike unexpectedly, breakers trip when heating comes on, or comfort remains poor. A qualified HVAC technician can perform a load calculation, inspect system controls, verify airflow and ductwork, and recommend alternatives or optimizations.

A professional can also evaluate whether a heat pump upgrade, duct sealing, or conversion to a dual-fuel setup would be more cost-effective over time than continued reliance on electric resistance heat.

Key Takeaways

• Definition: A heat strip for a heat pump is an electric resistance heating element used as supplemental or emergency heat.
• When It Runs: Activated during very cold weather, defrost cycles, or when the system is undersized for load.
• Efficiency: Less efficient than heat pump operation; increases electricity consumption when active.
• Sizing & Safety: Proper sizing, correct wiring, and safety switches are essential for safe operation.
• Alternatives: Cold-climate heat pumps, dual-fuel systems, insulation, and smart controls can reduce heat strip use.

Frequently Asked Questions

Do Heat Strips Damage The Heat Pump?

When properly installed and controlled, heat strips do not damage the heat pump. They are separate electric elements within the air handler. However, repeated unnecessary use can increase wear on air handlers and raise operating costs.

How Can A Homeowner Tell If The Heat Strip Is On?

Signs include noticeably warmer air during startup or when the heat pump seems insufficient, higher electric meter readings, and in some systems, indicator lights on the air handler. Technicians can verify by measuring current draw or checking control signals.

Is It Worth Replacing Heat Strips With A Gas Furnace?

Replacing heat strips with a gas furnace may lower operating costs in areas with low natural gas prices, but it requires separate ductwork compatibility and fuel infrastructure. Dual-fuel systems combine a heat pump with a gas furnace for optimized efficiency.

Can Smart Thermostats Reduce Heat Strip Use?

Yes. Smart thermostats can optimize setpoints and control strategies to minimize heat strip activation by avoiding abrupt temperature changes and using staged heating when available.

Resources And Further Reading

For detailed technical guidelines, consult the heat pump manufacturer’s installation manual, the National Electrical Code for electrical requirements, and ENERGY STAR materials on heat pump efficiency. Local utility programs and HVAC professionals can provide tailored advice and incentive information.

If questions remain about a specific system, a licensed HVAC technician should perform an on-site evaluation to ensure safe, code-compliant operation and to recommend energy-saving alternatives to extensive heat strip use.