Heat pumps are celebrated for their energy efficiency, but in colder climates, many systems use auxiliary heating to maintain comfort. Heat pump heat strips play a vital role in this process, ensuring homes stay warm even when outdoor temperatures plummet. This article explores how heat strips complement heat pumps, their benefits, design considerations, energy usage, and what homeowners should know before installing or upgrading a system.
Summary Table: Heat Pump Heat Strips Key Facts
| Feature | Details |
|---|---|
| Purpose | Provides supplemental/backup heating in cold temperatures |
| Location | Installed in air handler with the main heat pump |
| Common Sizes | 5 kW, 10 kW, 20 kW |
| Energy Use | Less efficient than heat pumps, but reliable when needed |
| When Activated | When outdoor temperature drops below heat pump efficiency threshold |
What Are Heat Pump Heat Strips?
Heat pump heat strips, often referred to as emergency or auxiliary heat strips, are electric resistance heaters located in the air handler of a heat pump system. They serve as a secondary or backup heat source when outside temperatures are too low for the heat pump to efficiently extract warmth from the air.
Most user-friendly heat pumps in the United States will automatically engage these strips under certain conditions. Their activation ensures that the home’s interior remains comfortable, even during adverse winter weather.
How Heat Strips Work: The Science Behind Supplemental Heating
While a heat pump draws warmth from outdoor air via refrigeration cycles, its efficiency drops as ambient temperatures fall below 35°F to 40°F. At that point, heat strips—essentially giant versions of the heating element in an electric toaster—are energized. They immediately warm the air passing through the system before it is blown into living spaces.
This process is simple but energy-intensive: electric current moves through high-resistance coils, producing heat by electrical resistance. The blower fan then distributes this warmed air throughout the home.
When Do Heat Pump Heat Strips Turn On?
Heat strips typically engage under a few scenarios:
- Low Outdoor Temperatures: When the heat pump alone cannot provide enough heat.
- Defrost Mode: While the heat pump is thawing itself, the strips keep the supply air warm.
- Emergency Heat: If you manually turn the thermostat to emergency mode, bypassing the main heat pump function.
Automatic controls manage this process, requiring little to no intervention from the homeowner under normal conditions.
Types Of Heat Strips And Their Sizes
Heat strips come in a range of sizes, most commonly between 5 kilowatts (kW) and 20 kW. The right size depends on your system’s total heating demand, climate, and other factors. HVAC contractors often recommend:
- 5 kW for smaller homes or milder climates
- 10 kW for average-sized houses
- 15-20 kW for large homes or areas with frequent cold snaps
Some systems allow multiple strips to stage (activate in increments) as needed, which can improve energy management and prevent unnecessary electrical demand spikes.
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Advantages Of Heat Pump Heat Strips
While heat strips are not the most efficient heating method, they offer several considerable benefits:
- Reliable Backup: Ensures your home stays warm even in extreme cold when the heat pump is inadequate.
- Automatic Operation: Most systems use integrated controls, requiring no manual intervention.
- Simple Design: Fewer moving parts reduce risk of mechanical failure compared to gas furnaces.
- Clean Heat Output: As electric heaters, they produce no indoor air pollutants or combustion gases.
Potential Drawbacks And Limitations
Despite their reliability, heat strips have key disadvantages that are important to understand:
- High Electric Consumption: Resistance heating is less efficient and more costly than running the heat pump alone.
- Can Cause High Utility Bills: Frequent or prolonged activation can lead to significant electricity costs.
- Limited By Electrical Capacity: Some older homes may not have adequate wiring or service panel size to support large heat strip operations.
Heat Strip Efficiency Compared To Heat Pumps And Other Heaters
Electric heat strips operate at nearly 100% efficiency in converting electrical energy to heat. However, heat pumps are much more efficient under normal weather, often delivering 2-3 times the heat energy for each unit of electricity by moving warmth rather than generating it outright.
| Technology | Seasonal Efficiency (HSPF/COP) |
|---|---|
| Heat Pumps | COP 2.5–4.0 (250–400% efficiency under optimal conditions) |
| Heat Strips | 100% efficiency (COP 1.0) |
| Gas Furnaces | 80–98% efficiency (depending on model) |
Cost Of Operation: What To Expect On Your Energy Bill
Heat strips can be expensive to operate, as they use more electricity per hour than a heat pump in standard heating mode. The operational cost depends on:
- Strip wattage (e.g., 10 kW = 10,000 watts)
- Electricity rate (typically $0.10–$0.20 per kWh in the US)
- Duration of use
Running a 10 kW heat strip for one hour uses 10 kilowatt-hours of electricity—often costing $1–$2 per hour. If used frequently during cold spells, this can quickly add up on your monthly bill.
Integration With Smart Thermostats And Controls
Modern heating systems feature advanced thermostats and controls that optimize the use of heat strips. Smart thermostats can stage their activation or prevent them from running unnecessarily. Some models allow you to set temperature thresholds and schedules, alerting users when auxiliary heat is triggered to help manage comfort and costs.
Additionally, energy monitoring capabilities can show how often and for how long heat strips are used, helping homeowners adjust settings for greater efficiency.
Heat Strips Vs. Emergency Heat: Clearing Up The Confusion
Many American homeowners confuse auxiliary (aux) heat and emergency heat:
- Auxiliary Heat: Activates automatically when heat pump can’t keep up.
- Emergency Heat: Selected by the user; runs only the heat strips, disabling the outdoor heat pump unit.
Emergency heat is intended for true malfunctions or severe cold, not regular use. Relying on it exclusively can dramatically increase energy costs.
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Best Practices For Efficient Use Of Heat Strips
Because of their high energy draw, minimizing heat strip usage is crucial for energy-conscious households. Best practices include:
- Proper Insulation: Make sure your home is well insulated to reduce heat loss.
- Seal Air Leaks: Address gaps around doors, windows, and attic spaces.
- Maintain Your Heat Pump: Clean filters and schedule annual tune-ups to ensure optimal efficiency.
- Adjust Thermostat Gradually: Large, sudden increases in set temperature can trigger unnecessary use of heat strips.
- Use Programmable Or Smart Thermostats: These help manage temperature swings and limit auxiliary heat activation.
Do You Need Heat Strips In Your Heat Pump?
In southern US states, heat strips may rarely be needed because of milder winters. However, in northern regions, heat strips are essential for backup heating during extreme cold. HVAC professionals can determine the appropriate size and need for heat strips based on local climate data, home insulation, and system sizing.
How To Know If Your Heat Strips Are Running
Signs that your heat strips are engaged often include:
- Higher Electric Bills: Sudden spikes during cold months.
- Thermostat Display: Many modern thermostats show “AUX” or “EM HEAT” when strips are active.
- Warm Air Production: You may notice hotter-than-usual air compared to typical heat pump operation.
Installation And Safety Considerations
Installing heat strips should always be done by a licensed HVAC technician, as it involves wiring high-current electrical elements into the air handler. Safety devices such as thermal cutout switches and fuses are included to prevent overheating and electrical hazards.
Proper installation ensures compliance with the National Electrical Code (NEC) and local regulations.
Comparison: Heat Strips Vs. Alternative Backup Heaters
Some homeowners consider alternatives to electric heat strips in their heat pump systems. Options include:
- Dual-Fuel Systems: Combine a heat pump with a gas or oil furnace for cold weather backup—often more efficient where natural gas is available.
- Hydronic Coils: Use hot water from a boiler as supplemental heat.
- Portable Space Heaters: Not typically recommended due to safety risks and uneven heating.
Each approach has trade-offs in terms of cost, complexity, and efficiency.
Factors Affecting The Sizing Of Heat Strips
Proper sizing is critical to effectiveness and safety. Contractors will consider:
- Home’s Square Footage: Larger homes need more supplemental heat.
- Regional Climate: Colder regions require higher-capacity strips.
- System Design: The heat pump’s own capacity and efficiency, and the air handler’s capabilities.
- Electrical Service Limitations: Panel size and wiring must support the added electrical draw.
Cost Of Installation
The cost to add or upgrade heat strips varies based on the system’s size and complexity, with typical prices ranging from $400 to $1,500 when bundled with a new heat pump installation. Retrofitting older systems can cost more due to potential wiring upgrades or system modifications.
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Questions To Ask Your HVAC Contractor
Before purchasing or installing heat strips, American homeowners should ask:
- Is my home’s electrical panel capable of supporting heat strips?
- What size strips are recommended for my climate and building size?
- How will the heat strips integrate with my thermostat and controls?
- What energy usage should I anticipate, and how can I minimize it?
Maintenance Tips For Longevity And Performance
Annual system tune-ups, including inspection and cleaning of the coils, ensure safe operation. Watch for signs of electrical burnout or tripped safety switches, and replace air filters regularly to maintain airflow and efficiency.
Government Incentives And Energy Star Considerations
In the US, some regional and federal programs offer rebates or incentives for installing high-efficiency heat pumps. However, these incentives rarely apply specifically to heat strips. Look for systems bearing the Energy Star label, as they are optimized for energy savings, including intelligent control of auxiliary heating.
Future Trends: Smarter, More Efficient Backup Heat
The move toward electrification of home heating has increased the importance of efficient backup heat sources. Newer heat pump models can now operate at rapidly falling temperatures without the need for frequent auxiliary heat, reducing reliance on resistance heat strips. Smart home integration and advanced compressor technologies also continue to improve efficiency and comfort for American homes.