Air-Source Heat Pumps | Department of Energy

Author: Geym

Aug. 11, 2025

Air-Source Heat Pumps | Department of Energy

An air-source heat pump can provide efficient heating and cooling for your home. When properly installed, an air-source heat pump can deliver up to two to four times more heat energy to a home than the electrical energy it consumes. This is because a heat pump transfers heat rather than converting it from a fuel, like combustion heating systems.

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Air-source heat pumps have been used for many years across the United States. Recent advancements in technology have made them a viable heating alternative even in regions with extended periods of subfreezing temperatures.

For example, a study by the Northeast Energy Efficiency Partnerships found that when units designed for colder regions were installed in the Northeast and Mid-Atlantic regions, annual savings were around 3,000 kWh (or $459 at $0.153/kWh) compared to electric resistance heating, and 6,200 kWh (or $948 at $0.153/kWh) compared to oil systems. When displacing oil, the average annual savings are nearly 3,000 kWh (or about $300).
 

How Air-Source Heat Pumps Work

A heat pump's refrigeration system consists of a compressor and two copper or aluminum coils (one indoors and one outside) with aluminum fins to aid heat transfer. In heating mode, heat energy is extracted from the outdoor air and brought into the house via a compressor circulating refrigerant. A reversing valve changes the direction of refrigerant flow for cooling and for the winter defrost cycle. In warmer months, heat is extracted from the home and rejected outdoors.
 

Efficiency and Performance

Today's air-source heat pumps are more efficient due to several technical advances:

  • Electronic and Thermostatic Expansion Valves: Provide more precise control of the refrigerant flow to the indoor coil.
  • Variable Speed Blowers: More efficient and reduce airflow during part-load conditions, compensating for restricted ducts, dirty filters, and dirty coils.
  • Improved Coil Design: Thicker coils yield better dehumidification.
  • Advanced Motor and Compressor Designs: Inverter-driven systems adjust infinitely between low and high speeds, providing exceptional energy savings and improved humidity control.

Types of Air-Source Heat Pumps

When choosing an air-source heat pump, it's essential to understand the different configurations available. These systems can be tailored to suit various home layouts, preferences, and heating and cooling needs. Here's an overview to help you make an informed decision:

  1. Ductless vs. Ducted vs. Short-Run Ducted:
    • Ductless Systems: Require minimal construction, ideal for additions, studio apartments, or smaller homes. They avoid ductwork efficiency losses but lack high efficiency MERV (Minimum Efficiency Reporting Value) air filtration or the ability to add ventilation.
    • Ducted Systems: Use existing ductwork, ideal for homes with a ducted heating or cooling system.
    • Short-Run Ducted: Use traditional ductwork in a small section of the house, often complemented by ductless units.
  2. Split vs. Packaged:
    • Split Systems: Have one coil and fan inside and one outside. Supply and return ducts connect to the indoor central coil and fan.
    • Packaged Systems: Contain all components in one outdoor unit. Heated or cooled air is delivered via ductwork passing through a wall or roof.
  3. Multi-Zone vs. Single-Zone:
    • Ducted Systems: Single-zone systems have one thermostat; multi-zone systems have motorized zone dampers and multiple thermostats.
    • Minisplit Systems: Single-zone systems have one outdoor condenser matched to one indoor head; multi-zone systems can connect multiple indoor heads to one outdoor condenser, allowing for individual room temperature control.

Selecting a Heat Pump

Every residential heat pump sold in the United States has an EnergyGuide label displaying its heating and cooling efficiency ratings.

  • Heating Efficiency (HSPF): The Heating Season Performance Factor measures the total heat provided over a heating season divided by the total electrical energy consumed. For example, a 10.3 HSPF heat pump provides 10,300 Btu of heat for every kWh of electricity consumed. In comparison, an electric resistance heating element provides only ~3,400 Btu of heat for every kWh of electricity consumed.
  • Cooling Efficiency (SEER): The Seasonal Energy Efficiency Ratio measures the total heat removed over a cooling season divided by the total electrical energy consumed. For example, a 16 SEER cooling system provides 16,000 Btu of cooling for every kWh of electricity consumed.

In general, the higher the HSPF and SEER, the higher the cost of the unit. However, the energy savings can return the higher initial investment several times during the heat pump's life. A new central heat pump replacing a vintage unit will use much less energy, substantially reducing air-conditioning and heating costs.

As of January , more stringent efficiency terms (HSPF2 and SEER2) were enacted to better reflect airflow resistance due to more realistic duct systems. For example, a unit rated at 15 SEER would be a 14.3 SEER2. Likewise, an 8.8 HSPF would equate to a 7.5 HSPF2 heating efficiency.

These are some other factors to consider when choosing and installing air-source heat pumps:

  • Select a heat pump with a demand-defrost control. This will minimize defrost cycles, thereby reducing supplementary and heat pump energy use.
  • Fans and compressors make noise. Locate the outdoor unit away from windows and adjacent buildings, and select a heat pump with a lower outdoor sound rating (decibels). You can also reduce noise by mounting the unit on a noise-absorbing base.
  • The location of the outdoor unit may affect its efficiency. Outdoor units should be protected from high winds, which can cause defrosting problems and may need to be elevated due to snow build-up.

To choose an electric air-source heat pump, look for the ENERGY STAR® label. In warmer climates, SEER is more important than HSPF. In colder climates, focus on getting the highest HSPF feasible.

Performance Issues with Heat Pumps

Heat pumps can experience issues with poor airflow, restrictive or leaky ducts, incorrect refrigerant charge, and improper wiring of electric resistance auxiliary heat strips. To ensure your heat pump operates efficiently and to avoid these performance issues, it’s essential to hire a qualified technician.

Consumers should seek out technicians certified by programs recognized under the DOE’s Energy Skilled Heat Pump Programs. This program identifies organizations that certify technicians and training programs for heat pumps, ensuring the technician has the necessary expertise to install and service the system correctly.

Finding a skilled, knowledgeable contractor is one of the most important steps to ensure the long-term performance of your HVAC equipment. It’s also one of the biggest barriers for consumers, after first cost. Be sure to hire someone certified by a recognized program to get the most out of your heat pump system.

  • Ensure there is about 400 cubic feet per minute (cfm) airflow for each ton of the heat pump's air-conditioning capacity. Efficiency and performance can deteriorate if airflow is much less than 350 cfm per ton. Technicians can increase airflow by cleaning the evaporator coil or adjusting the fan speed, but often some modification of the ductwork is needed. See minimizing energy losses in ducts and insulating ducts for more information. 
  • Refrigeration systems should be leak-checked at installation and during each service call. Packaged heat pumps are charged with refrigerant at the factory and are seldom incorrectly charged. Split-system heat pumps, on the other hand, are charged in the field, which can sometimes result in either too much or too little refrigerant. Split-system heat pumps that have the correct refrigerant charge and airflow usually perform very close to the manufacturer's listed SEER and HSPF. Too much or too little refrigerant, however, reduces heat-pump performance and efficiency. For more maintenance tips, see the Energy Star maintenance checklist.
  • Energy codes require that heat pumps with auxiliary electric resistance back-up heat have controls to prevent unnecessary heat strip operation. This is one of the most commonly violated installation practices for heat pumps.

Conclusion

Air-source heat pumps provide efficient and effective heating and cooling for homes in various climates. By selecting the right type and ensuring proper installation, you can enjoy significant energy savings and improved comfort.

Take Action

For more information and to find ENERGY STAR certified air-source heat pumps, visit the ENERGY STAR website. Ensure your system is installed correctly and maintained regularly to maximize efficiency and savings.

To find technicians certified under the DOE Energy Skilled Heat Pump Programs, visit the DOE Energy Skilled Heat Pump Programs page. Choosing a certified technician ensures proper installation and maintenance, helping to avoid performance issues and achieve long-term energy savings.

Heat Pump Buying Guide: The Complete Checklist - Trane®

Electrification8 min read

By Anne Fonda

What Is a heat pump?

While heat pumps are becoming more and more popular, don’t feel bad if you don’t know a lot about them. An electric air source heat pump is typically an outdoor unit that both heats and cools your home. They are alternatives to the standard central air conditioners and furnace systems.

How does a heat pump work? That’s another question we get a lot. Essentially, a heat pump uses heat energy and through heat exchange, transfers it to a cooler environment. 

This means the air source unit takes the heat in the outside air and transfers it into your home in the winter. It then reverses the process and transfers heat inside your home to the outside in the summer. 

For a more detailed explanation, read our blog on demystifying heat pumps.

What are the benefits of a heat pump system?

  • They are highly efficient.
  • Heat pumps use electricity, meaning they don’t burn any fossil fuels, and therefore reduce your climate footprint.
  • A heat pump system can provide long-term cost savings on your energy bills.

How to choose the right heat pump

Choosing the right unit starts with asking some questions and finding the right answers. Some top heat pump considerations are size, energy efficiency, cost, and brand. Keep reading to learn more about each factor.

1. What size heat pump do I need?

Determining the correct sizing for your home involves either the Manual J load calculation or estimating based on the square footage of your home. 

Manual J load calculation

The Manual J load calculation is a series of calculations that HVAC contractors or technicians use to determine how much heating or cooling your home needs. It includes several factors, including:

  • The square footage of your home
  • Height of the ceilings
  • Your home’s insulation
  • Your climate and how many days you will need heating and cooling
  • How often you use the space (does anyone work from home?)
  • How many people use the space
  • Heat-producing appliances
  • Your preferred temperature
  • Number of exterior doors
  • Number of windows

The technician enters these numbers into a formula to determine the precise size of the unit you need. 

A calculation that is simpler but not as precise is calculating the size heat pump you need based on your home’s square footage. In general, Every 500 square feet needs a capacity of one ton for air conditioning. 

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For example, a -square-foot home would need a 3-ton unit, and a -square-foot home would need a 5-ton unit. But you also need to understand what each ton means in British Thermal Units (BTUs). You might find the chart below helpful in sizing your heat pump. 

Home size (sq. ft.)Heat Pump Size (tons)Heat Pump Size (BTUs)500 sq. ft.1-ton heat pump12,000 BTUs sq. ft.2-ton heat pump24,000 BTUs sq. ft.3-ton heat pump36,000 BTUs sq. ft.4-ton heat pump48,000 BTUs sq. ft.5-ton heat pump60,000 BTUsHome size (sq. ft.)Heat Pump Size (tons)Heat Pump Size (BTUs)500 sq. ft.1-ton heat pump12,000 BTUs sq. ft.2-ton heat pump24,000 BTUs sq. ft.3-ton heat pump36,000 BTUs sq. ft.4-ton heat pump48,000 BTUs sq. ft.5-ton heat pump60,000 BTUs

2. What energy efficiency ratings should I look for?

In general, we would recommend opting for the most energy-efficient heat pump you can afford. Prices generally go up the larger the unit and the higher the energy efficiency. But remember that the more efficient a unit is, the more it can save you on heating and cooling costs in the future.

SEER2

SEER stands for Seasonal Energy Efficiency Rating, and SEER2 is the latest version that took effect in . It measures the cooling efficiency of air conditioning units and heat pumps. The higher the SEER2 rating, the more efficient the unit is. 

HSPF2

HSPF2  stands for Heating Seasonal Performance Factor and HSPF2 is the latest standard that took effect in . It’s a measurement of how effectively your heat pump can heat your home in the colder months. The higher the rating, the more efficient the unit is in heating mode.

3. What does a heat pump cost?

There is no simple answer to this question because we don’t know all the factors - the size of your home, the type of unit you need/want, and more. In general, the cost of getting a heat pump installed will be more than a standard system with an outdoor AC unit and an indoor furnace. For Trane products specifically, we provide a price range for some units in our pricing guide.

But because of the increased energy efficiency, you may see a near-immediate decrease in your heating and cooling bills, which will last for the life of your system. Add to that the availability of federal heat pump tax credits (up to $2,000) for Energy-Star-qualified units, and buying a heat pump can become a cost-effective home improvement.

You can also use the Energy Star Rebate Finder, which can help you find state and utility company rebates in your area.

4. What brand should I buy?

Research reputable brands in the heat pump industry. Check reviews from websites such as Consumer Reports and others. Look for brand reputation, reliability, and quality. Trane recently achieved the honor of being ranked as the Most Trusted® HVAC Brand for the 10th year in a row, and we are excited to share this news.

You can explore our heat pumps to see the features and efficiency ratings available.

Consider a dual fuel system

If you live in a colder climate such as Minnesota, you may be wondering if a heat pump vs furnace is right for your home. Heat pumps are very common in the southern states, but heat pumps in cold climates are a viable heating solution when you install a dual-fuel system. 

This is when you install a cold climate heat pump that can operate efficiently in colder temperatures, and connect it to a gas furnace, which kicks in only in extreme temperatures that the heat pump can’t handle. 

You get the energy efficiency of the heat pump and you pay less for natural gas or propane. Plus, you get air conditioning during those summer heat waves that are growing more common in northern climes.

Consider a mini-split heat pump/ductless heat pump system

A mini-split heat pump, also known as a ductless heat pump, is a heating and cooling system designed for rooms or spaces that don’t have ductwork. This could include a garage, an enclosed porch, an attic, or a lake cabin - you get the idea. 

Options include:

  • Mini-split single-zone heat pump for one space, such as a garage or enclosed porch
  • Multi-split ductless system,s where you can heat and cool up to five spaces without ductwork. This can be a great option for a remote cabin, an older building, or even a historic home where installing ductwork would be cost-prohibitive. 

An experienced HVAC contractor can help you determine the best solution for your home.

Find the perfect HVAC contractor for heat pump installation

Finding the right HVAC contractor for your heat pump installation doesn’t have to be hard. But it will require some research. Here are some quick tips on steps to take to find the right company to do the job:

  • Ask friends and family for recommendations. NextDoor and Facebook community groups are also good places to ask for recommendations.
  • Google heat pump installation near me and check out the top 5 results, visiting their websites for valuable information.
  • Look for industry credentials and certifications, as well as licenses where applicable.
  • Read their reviews and customer testimonials, and look for how responsive they are to negative feedback, if any.
  • Confirm that they offer HVAC maintenance and repair services as well as installation.
  • Choose 2-3 HVAC contractors to visit your home and discuss the type of heat pump system they recommend for your needs, and the sizing that will offer the best comfort and efficiency.
  • Discuss the installation process and timeline with each contractor.
  • Discuss project cost and any financing options.
  • Choose the company you want to work with.

Be sure to keep your receipts for the work you have done and the certificates for the equipment you have installed so that you can claim your tax credits when you file your taxes. Enjoy the comfort of a new heat pump system and watch your utility bills go down.

Are you ready to upgrade your heating and cooling system? From a standard heat pump system to a dual fuel system to a mini-split system, your local Trane Comfort Specialist can help you make the right choice for your home and your family. Reach out today to find the perfect heating and cooling solution for your home. 

Anne Fonda, Content Writer

LinkedIn

A Content Writer with Trane Technologies, Anne Fonda researches topics and writes for Trane® and associated residential HVAC brands. She works in collaboration with Trane Technologies subject matter experts, offering easy-to-understand, informative content on complex topics. Her goal is to help consumers make informed decisions on the products and services they need.

She has written for HVAC and other service provider websites for over 16 years. Before transitioning to web content writing, Anne had a 14-year stint as an award-winning journalist. She graduated cum laude from the University of Missouri-Columbia School of Journalism.

When she’s not working, Anne enjoys playing word games, reading, gardening, spending time with family, and visiting gardens and museums.

Expert review by Mark Woodruff, Senior Product Manager, Ducted Outdoor

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