Heat Strips For AC Unit: Comprehensive Guide to Types, Installation, Efficiency, and Cost

Heat strips for AC units are essential for providing supplemental heating, especially in climates with occasional cold snaps. This article delves into what heat strips are, their types, compatibility with AC units, installation tips, energy efficiency, and cost considerations. Whether you’re a homeowner or an HVAC professional, this guide offers valuable insights for optimizing year-round comfort.

Aspect	Key Details
What Are Heat Strips?	Electric coils added to air handlers for supplemental heat
Main Types	Single-stage, multi-stage, variable output
Typical Sizes	Ranges from 3 kW to 20 kW
Common Usage	With heat pumps, packaged ACs, split systems
Average Cost (Installed)	$300 – $1,000 (varies by size & labor)
Energy Efficiency	Near 100% conversion, but high electrical consumption

What Are Heat Strips for AC Units?

Heat strips are electric resistance heating elements installed within air handlers or furnaces. They’re designed to supplement the heating process, especially when outside temperatures dip below the efficient range for heat pumps. Essentially, they function like large versions of the heating coils found in electric toasters or space heaters, producing heat as electrical current flows through them. This allows an AC unit (especially a heat pump) to provide warm air even in frigid weather.

How Heat Strips Work

Heat strips operate on the principle of electrical resistance. When a thermostat signals a need for heat, electrical current passes through the metal coils within the strip, creating thermal energy. This heat is then distributed by the AC system’s blower through the ductwork into your living spaces. They’re often called “auxiliary heat” or “emergency heat” when paired with heat pumps because they’re used when the primary heating source struggles in very low temperatures.

Types of Heat Strips Used in AC Units

Single-Stage Heat Strips

Single-stage heat strips provide full heating power anytime they’re activated. They’re the most basic type and switch on at full capacity when extra heat is needed, either manually (via “emergency heat” mode) or automatically as outdoor temperatures drop. While reliable, these can cause sudden spikes in electricity usage.

Multi-Stage Heat Strips

Multi-stage heat strips allow for staged heating and greater energy efficiency. These systems energize only part of the strip at lower temperatures and escalate to full power as needed. This not only saves energy but helps maintain more comfortable temperature levels throughout the home without sudden jumps in warmth or utility cost.

Variable Output (Modulating) Heat Strips

Variable output heat strips are advanced and adjust output dynamically. They automatically tailor their operation depending on current heating demand, further optimizing energy use and maintaining precise comfort.

Specialty Heat Strips

Specialty or custom heat strips may be required for large commercial systems or specialty applications where unique voltage or sizing is needed. HVAC professionals can specify custom setups according to building parameters.

Compatibility: Which AC Units Use Heat Strips?

Heat strips are compatible with several types of air conditioning systems, especially those designed to offer both heating and cooling:

• Heat Pumps: Most commonly paired with heat pumps, which struggle in very cold weather.
• Packaged Units: Both packaged AC and heat pump systems can include heat strips as factory or field-installed options.
• Split Systems: Central air handlers in split systems can often incorporate electric heat strips.
• Ductless Mini-Splits: Some models offer optional heat strip kits, but this is less common than with central systems.

Not every standard AC relies on heat strips for heating. Traditional central air conditioning (cooling-only) units require a separate heating system, such as a furnace.

What Size Heat Strip Do You Need?

Selecting the correct size heat strip is crucial for efficiency and safety. Headquarters recommend using a licensed HVAC professional for sizing calculations. The required kW capacity depends on:

• Square footage and layout of your home
• Insulation values and window efficiency
• Local climate and average winter lows
• System air handler capacity and electrical infrastructure

Common heat strip sizes for residential systems range from 3 kW to 20 kW. As a rule of thumb, many homes use a 10 kW strip for average supplemental heating needs. Oversized or undersized heat strips lead to inefficiency, safety hazards, or cold spots.

The Installation Process for Heat Strips

Installing heat strips in an AC system is a technical process best performed by certified HVAC professionals due to the electrical and safety considerations involved. Here are the main installation steps:

Installation Steps

1. Power is shut off to the system at the breaker to prevent hazards.
2. The air handler’s access panel is removed to expose the internal compartment.
3. The heat strip assembly is mounted in the designated slot within the air handler.
4. Electrical wiring is connected, ensuring appropriate breakers and conductors are used.
5. The installer secures all connections, replaces the access cover, and restores power.
6. The system is tested for proper operation and safety cut-offs are confirmed.

Incorrect installation of heat strips can pose fire risks and potentially void equipment warranties. Professional installation is strongly recommended to comply with local codes and manufacturer requirements.

Heat Strips vs. Other Supplemental Heating Options

Heating Method	Energy Source	Target Use	Pros	Cons
Heat Strips	Electric	Supplemental/backup	Simple, reliable, no combustion gases	High electrical use
Gas Furnace	Natural Gas/Propane	Primary or backup	Lower operating cost, high output	Requires gas, venting system
Space Heaters	Electric or Fuel	Room-by-room	Portable, inexpensive upfront	Inefficient for large areas, safety risk
Baseboard Heaters	Electric	Room-by-room	Individual room control	High cost, uneven comfort

Heat strips are ideal for whole-home backup heating but may not be the most cost-effective solution for primary heating in colder climates compared to other systems like gas furnaces.

Energy Efficiency of Heat Strips in AC Units

Electric heat strips are nearly 100% efficient at converting electricity to heat inside the home. However, electricity is generally more expensive than gas or heat pump-generated heat. Therefore, running heat strips for prolonged periods can quickly increase utility bills. Heat pumps are more efficient below about 35°F, but strips help maintain comfort during brief or severe cold spells.

• If your climate experiences only brief cold snaps, heat strips offer practical, on-demand backup.
• For extended cold climates, consider primary heating options with lower operational cost.

Operating Modes: Auxiliary and Emergency Heat Explained

Modern thermostats and heat pumps featuring heat strips will have two key operating modes:

• Auxiliary Heat: Kicks in automatically when the heat pump alone can’t keep up in colder weather, helping maintain your set temperature.
• Emergency Heat: Engaged manually, this bypasses the heat pump entirely in favor of heat strip operation due to heat pump failure or extreme cold below system capability.

Frequently relying on emergency heat significantly increases energy costs, so it should only be used as necessary during equipment issues or severe weather extremes.

Control and Safety Features for Heat Strips

Well-designed heat strip setups include several safety and control features. These ensure optimal function and prevent hazards:

• Thermal Cut-Off Switch: Automatically disables the strip in case of overheating.
• Airflow Sensors: Ensures the blower is operational before energizing the strips to prevent overheating.
• Sequencers and Relays: Stagger power to strips for reduced electrical surges and increased longevity.
• Integrated Thermostat Controls: Modern smart thermostats optimize when and how heat strips are activated.

These features work together to ensure safe, consistent, and efficient heat delivery while protecting your equipment and home.

How Much Does It Cost to Install Heat Strips for Your AC Unit?

Heat strip installation costs vary significantly according to system size, type, and existing wiring, but here are average estimates for homeowners and property managers:

• Parts Only: A basic heat strip kit (sizes 5–20 kW) typically costs $80–$300.
• Installation Labor: Expect $200–$700 for professional installation, depending on complexity and electrical upgrades.
• Total Cost (Installed): Most projects fall between $300 and $1,000. Larger, multi-stage, or commercial systems can exceed $1,500.

NEVER attempt DIY installation unless you’re a qualified electrician with HVAC experience and permits. Most manufacturers require proof of professional installation for warranty coverage.

Maintenance Requirements for Heat Strips

Heat strips have relatively low maintenance requirements, but routine inspection during regular HVAC service visits is important. Recommended maintenance includes:

• Checking electrical connections and securing terminals
• Removing any dust or debris buildup
• Testing cut-off switches and relays
• Ensuring proper sequencing and operation during test cycles

Professional inspections every 1–2 years extend the lifespan and ensure safety. Dirty or malfunctioning strips can overheat, waste energy, or fail to deliver supplemental heat effectively.

Common Problems and Troubleshooting Heat Strips

Heat strips are robust but may experience certain issues:

• Failure to heat: Often caused by tripped breakers, blown fuses, faulty sequencers, or broken coils.
• Overheating: Typically due to failed air flow sensors, improper installation, or clogged filters reducing air flow.
• Short cycling: Can be caused by thermostat or control board malfunctions.
• Regular HVAC service can diagnose and repair most heat strip issues, avoiding costly downtime during cold weather.

Pros and Cons of Heat Strips for AC Units

Pros	Cons
Simple, reliable supplemental heating Direct fit in compatible AC air handlers No combustion, no venting required Immediate warmth for brief cold periods Automatic operation with compatible thermostats	High electric usage & cost if run extensively Not suitable as primary heat in cold climates Requires properly sized electrical breakers Can reduce system lifespan if overused

When Should You Consider Adding Heat Strips?

Heat strips are most beneficial for homes with heat pumps in moderate climates, where occasional freezing temperatures can outpace what a heat pump alone provides. If your area rarely dips below 35°F but occasionally experiences single-digit cold snaps, heat strips offer reliable emergency backup. They’re also a sensible add-on when installing a new air handler, offering balanced year-round comfort without major upgrades.

Tips for Energy Efficient Use of Heat Strips

• Only engage “emergency heat” mode when necessary—such as during heat pump failure or extreme cold emergencies.
• Use programmable thermostats to minimize unnecessary run time.
• Seal air leaks and improve insulation for better retention of heated air.
• Schedule annual HVAC maintenance to maximize system efficiency.
• Upgrade to multi-stage or variable output strips for more efficient supplemental heat.

Frequently Asked Questions (FAQs) About Heat Strips for AC Units

Question	Answer
Can I add heat strips to my existing AC unit?	Most modern air handlers can accommodate heat strips, but older models or cooling-only systems may not be compatible. Consult your HVAC provider.
Does it cost a lot to run heat strips?	Heat strips consume significant electricity—each kilowatt costs about 12–18 cents per hour. Use only for brief supplemental heating to control costs.
Are heat strips safe?	When professionally installed and maintained, heat strips are safe, thanks to built-in thermal cut-offs and airflow protections.
How long do heat strips last?	With proper maintenance, heat strips typically last 10–15 years, often matching the lifespan of the AC unit itself.
Can I use heat strips as my sole heating source?	In mild climates, yes, but in colder areas, dedicated heating systems are more cost-effective and reliable for primary use.

How to Choose the Best Heat Strip for Your AC Unit

Choosing the right heat strip involves more than size—it’s about matching your comfort needs with your AC system’s capabilities. Here are key considerations:

• System Compatibility: Confirm your air handler is rated to support supplemental electric heat.
• Proper Sizing: Rely on HVAC Manual J calculations or professional guidance.
• Type of Strip: Consider multi-stage or variable output for better comfort and efficiency.
• Warranty: Opt for strips with a strong manufacturer warranty when installed by licensed professionals.
• Safety Certifications: Look for UL or ETL certification for peace of mind.

Consulting with a qualified HVAC professional ensures correct product selection, installation, and operation—maximizing comfort and protecting your investment.

Summary of Heat Strips for AC Units

Heat strips are an effective and reliable solution for supplemental heating needs in homes with compatible AC systems. They operate on simple electrical resistance principles but require careful installation, proper sizing, and regular maintenance. While almost 100% efficient in converting energy, they are best used as auxiliary heat due to high operational costs compared to other heating methods. Properly integrated in heat pump systems, heat strips deliver consistent warmth during cold snaps, ensuring year-round comfort for American households.