Watt, Why & How e-Newsletter

How Do They Do That? Heating Homes With Cold Air

How Do They Do That?An air-source heat pump is an energy-efficient heating and cooling system that uses outside air as its heat source. With energy-efficiency ratings of well over 100 percent, such heat pumps provide year-round comfort in millions of U.S. homes. But how do heat pumps use cold air for heating, and how do you get energy efficiency of more than 100 percent out of any device?

How they work

Heat pumps provide both heating and cooling. During the heating season, heat pumps move heat from the cold outdoors to the warmer indoor space. How does cold air provide heat? Hot and cold are relative terms. All outside air down to absolute zero (-460°F) contains some heat. An air-source heat pump extracts some of this heat and moves it indoors to provide space heating.

A heat pump system consists of a compressor and two coils made of copper tubing; one coil is located indoors and the other one is located outdoors. In the winter, liquid refrigerant in the outdoor coil converts into a gas after absorbing heat from the air. In the indoor coil, heat is released from the gas refrigerant as it condenses back into liquid. In the summer, this process is reversed; the heat pump provides cooling by moving heat from warm inside air outdoors.


Source: http://www.energystar.gov/
Air-source heat pump
Heat pump efficiency

How do heat pumps have efficiencies greater than 100 percent? Because heat pumps move or pump heat, rather than create it. A conventional furnace creates its own heat by burning fuel. Combustion losses result in an energy efficiency of less than 100 percent. While a furnace can achieve a high efficiency level, the amount of heat produced is ultimately dependent on the amount of fuel used.

Since heat pumps are merely moving heat from one place to another, they are not bound by such restrictions. Heat pumps still use energy, just not nearly as much as the heat energy they move. When properly installed, an air-source heat pump delivers one-and-a-half to three times more heat energy to a building than the electrical energy it consumes, according to the U.S. Department of Energy. This translates into energy efficiencies of 150 to 300 percent. The measure of heating efficiency is the Heating Seasonal Performance Factor (HSPF) in units of Btu heat output divided by watt-hours of electricity input (6.8 HSPF = 200% efficiency).

Air-source heat pumps lose both efficiency and heating capacity as the outdoor air temperature decreases. When outdoor temperatures drop below 32°F, a less efficient, electric resistance or gas-fired backup system kicks in to provide extra heating capacity. For this reason, standard air-source heat pumps are not always the most cost-effective heating option in areas with cold winters. Though cold-climate heat pump models have been developed by some manufacturers, they are not yet widely available. In moderate climates, however, heat pumps can provide highly efficient and economical space conditioning all year long. 

More From APCO

Sign Up Now Pay Online for Free with Paperless Billing

Pay Online for Free with Paperless Billing

Learn more

Download our new app

How We Restore Power Learn more

How We Restore Power

Learn more Create Your Own Emergency Outage Kit

Create Your Own Emergency Outage Kit

Visit AEP.com
Use of this site constitutes acceptance of the AEP Terms and Conditions. View our Privacy Policy. © 1996-2019 American Electric Power. All Rights Reserved.

Privacy Policy

Privacy Policy for Appalachian Power, a unit of American Electric Power (AEP)


This Privacy Policy applies only to AppalachianPower.com and the Appalachian Power customer mobile app (com.aep.customerapp.apco). Other AEP websites and apps may be governed by their own privacy policies, appropriate to the uses and needs of each. Throughout the site or app, we may provide links to resources and sites that are not part of AppalachianPower.com or the Appalachian Power customer mobile app. This Privacy Policy does not apply to those resources and sites.


By using this site or app, you consent to the terms of this Privacy Policy. Whenever you submit information via this site or app, you agree to the collection, use, and disclosure of that information in accordance with this Privacy Policy.

Information Collected

  1. Passively collected information

    During your use of this site or app, we may collect anonymous information about your visit here through the use of server logs, cookies, scripts, tracking pixels and other Web traffic tracking systems. This information is aggregated and used to improve user experience through analysis of user activities. This information is never combined with any of the personally identifiable information you may provide in your use of the features of this site or app.
  2. Personally identifiable information

    On certain forms of this site or app, you may be asked to provide information about yourself or your account with us, either to identify yourself to us or to request a service from us. In each case, we will inform you what information is provided at your option and what information is required to complete the transaction or activity you are engaged in. If you are unwilling to provide this required information, you will be unable to complete the requested transaction.

Use and disclosure of information

The information you provide to us will be used to respond to requests you may make for services. Some or all of this information may be added to your permanent account record and may be used for research purposes.

In addition, we may use elements of this information in the following situations:

  1. We may transfer the information to Appalachian Power’s affiliates and subsidiaries, unless such transfer is prohibited by law;
  2. We may transfer the information as part of a merger, consolidation, acquisition, divestiture or other corporate restructuring (including bankruptcy);
  3. We may make the information available to third parties who are providing the product, service or information that you have requested (but not your password);
  4. We may make such information available to third parties who are providing services to Appalachian Power (for example, providing the information to third parties performing computer-related services for Appalachian Power);
  5. We may use the information to communicate with you about products and services that may be of interest to you.
  6. We may disclose the information if we form a good-faith belief that disclosure of such information is necessary to investigate, prevent, or take action regarding any illegal activities or regarding interference with the operation of our site or violation of its terms of use; or
  7. We may disclose the information if we believe that disclosure is required by law or regulation or in response to a subpoena or other order of a court or other governmental agency.

Appalachian Power uses Flurry Analytics Service (provided by Yahoo) in order to improve its mobile apps. Flurry’s privacy policy governs the use of this information.

Also, Appalachian Power reserves the right to share any aggregated information (i.e., non-personally identifiable information) with any third parties for any reason, unless prohibited by law.

We will not sell, rent or otherwise disclose the information we gather about you or your account to any third party, except as outlined in this Privacy Policy.


Appalachian Power takes reasonable steps to protect your personally identifiable information as it is transferred to us, through the use of Web technologies such as the Secure Sockets Layer and others. However, no Internet transmission of information is ever completely secure or error-free. In particular, e-mail sent to or from Appalachian Power may not be secure.

How to Reach Us

If you would like to update your personally identifiable information or if you have questions about this privacy policy, please contact us.

Changes to This Policy

Appalachian Power reserves the right to change this Privacy Policy at any time. If this Privacy Policy changes, the revised policy will be posted to this site. Please review this Privacy Policy before you provide any personally identifiable information through this site. Use of our web site after the posting of a revised privacy policy constitutes your consent to the revised policy.

This policy was last revised on December 13, 2017.

Close ×

Sign Up For Alerts

Subscribing to APCO alerts gives you instant notification for:

  • Billing & Payments - avoid late payments and disconnection
  • Outage Updates - find out if there's an outage at your address and when power will be back on

Win an Xbox One with Alerts!

Enroll in alerts to be eligible to win. Subscribing to I&M alerts gives you instant notification for:

  • Billing & Payments - avoid late payments and disconnection
  • Outage Updates - find out if there's an outage at your address and when power will be back on

Loading video...