Heat Pumps

What is a Heat Pump?

A heat pump is a device that heats or cools a space by transferring thermal energy from a cooler area to a warmer one, using the refrigeration cycle. Like your refrigerator and traditional air conditioner, heat pumps use electricity to transfer heat from a cool space to a warm space, making the cool space cooler and the warm space warmer. During the heating season, heat pumps move heat from the cool outdoors into your warm house. During the cooling season, heat pumps move heat from your house into the outdoors. Because they transfer heat rather than generate heat, heat pumps can efficiently provide comfortable temperatures for your home (even when it’s very cold). ​

Why Should I Consider Switching to a Heat Pump?

Fossil gas furnaces burn gas to create heat in the home. During this process, it produces harmful ​emissions of nitrous oxides (NOx), carbon monoxide (CO), and particulate matter (PM), among others. These emissions can contribute to poor indoor air quality and health impacts (including asthma, allergies and learning deficits), as well as climate change. By switching to a heat pump, it eliminates gas combustion in the home, which in turn reduces harmful ​emissions and improves the air quality inside the home. 

Most homes in the Midwest are currently heated with fossil ​gas. Unfortunately, gas is primarily made up of methane, which is an extremely potent Greenhouse Gas (GHG)​, and a significant contributor to climate change. Methane leaks at a number of points along the path from extraction to transmission to distribution. Recent research indicates that reducing methane in our atmosphere is a powerful way for us to relatively quickly combat global warming, as methane breaks up more quickly than carbon, leading to more immediate slowing of temperature increases. By switching to a heat pump, homes can eliminate a source of methane, reducing their greenhouse gas emissions.

Heat pumps are much more efficient than a traditional furnace and air conditioner set-up. A heat pump is a device that warms or cools a space by transferring thermal energy from a cooler area to a warmer one, using the refrigeration cycle to reverse the flow of air. In the summer, a heat pump will pull warm air out of your home and deposit it outdoors, just as a conventional air conditioner would. In the winter, it pulls warm air from the outdoors (even when it’s very cold), compresses it to increase the temperature, and transfers that air into your home. Therefore, heat pump systems provide both heating and cooling with the same equipment. Heat pump systems have advanced in recent years and are extremely efficient, even in cold climates. ​Depending on the type of heat pump, they can see efficiency levels of 200% to 400%, meaning for each unit of energy they use, they provide two to four units of heating or cooling. Even the most highly efficient furnace has an efficiency level around 96%, resulting in it using more energy than the amount of heating it provides.  

For homes currently heating with resistance heat (approximately 22% of Ann Arbor), heat pumps are a much more efficient option and will save money. The same holds true when compared with window air conditioning units. 

While heat pumps require some learning for those of us accustomed to fossil gas furnaces, they can produce more even temperatures and greater comfort in the home. For example, heat pumps work better and more efficiently when the temperature is set to comfort and then left there instead of adjusting the thermostat at night or when leaving the home. They also cycle between heating and AC seamlessly, controlled by the smart thermostat that accompanies the heat pump.

Types of H​​eat Pumps​​

Air Source Heat Pumps (ASHPs) can either be ducted (working with an established duct system in a home) or ductless (often referred to as mini splits), and usually have an outdoor and an indoor component. They are easy to install, and can be customized very specifically to the needs of the home. They are considerably more energy efficient than fossil gas furnaces or resistance heaters (like baseboard units). 

Ground Source or Geothermal Heat Pumps (GSHPs) work in a similar way as ASHPs, but they transfer temperatures to and from the ground. They require digging wells for installation, and are therefore sometimes difficult to install on small city lots. As the ground temperature stays consistent throughout the year, they are extremely efficient. GSHPs currently qualify for a 30% federal tax credit, helping significantly with cost of installation. Learn more about geothermal heating and cooling. 

Can a Heat Pump Handle Ann Arbor's Cold Climate?

Despite clear efficiency and low-carbon benefits, heat pumps from 20 and 30 years ago struggled to operate in sub-freezing temperatures. Proven technical advances have drastically improved heat pump performance in cold climates; cold climate heat pump models maintain efficiency down to 5 deg F, and some are even able to perform below -10 deg F. These heat pumps have been successfully field tested in climates like Minnesota and the Arctic Circle. Improved integration with backup electric resistance systems provide an extra layer of security. 

The heat pumps of today are capable of far more than those from previous decades. In response to concerns about cold climate performance, cold-climate specific standards are being rapidly developed to provide real-world performance information on cold climates. Both the Northeast Energy Efficiency Partnership and the Canadian Standards Association are working on these standards.  ​

Additionally, ground source heat pumps use the temperature of the ground to transfer heat, which maintains a stable temperature regardless of the outdoor air temperature. Therefore, even as it gets extremely cold or hot, they maintain a similar level of efficiency. 

Water​​ Heaters and ​​Clothes Dryers

Heat Pump Hot Water Heaters and Clothes Dryers are a very viable option when replacing an old gas appliance. They work in a similar fashion to ASHPs, pulling heat out of the ambient air to warm the water or air. There are a number of manufacturers making heat pump water heaters now, including some with lifetime warranties. 

What is an Energy Audi​t​,​ and do I Need One?

Energy Audits provide a comprehensive assessment of how your home is functioning, whether air sealing or insulation could be improved, and whether older appliances are spiking electrical costs. They generally cost between $150-350, and can be performed by independent auditors or weatherization contractors. Weatherization is important in order to right-size your heat pump, and make sure it functions optimally. The City offers a more comprehensive assessment that includes a path to decarbonization (opportunities for electrification and solar in addition to energy efficiency and weatherization), and this is free for all Ann Arbor residents. See the A2ZERO Home Energy Advisor website for more information. 
Sticker saying next time I'll be a heat pump

​Sticker Campaign

Committing to replacing​ your current gas appliance with an electric heat pump option when the time comes? Join our sticker campaign. The QR code points to our website, which will be updated with educational materials, incentivization programs, and other useful materials around electrification. Grab a sticker at one of our OSI events or reach out to sustainability@a2gov.org to get one. 

Finding a Contractor​

Homeowners searching for contractors to help them switch from gas-burning furnaces to heat pumps, or to learn how to prepare their homes for future electrification or solar, are often met with conflicting advice and/or outdated information. The City of Ann Arbor has partnered with Michigan Saves to create an Electrification Badging program to help homeowners find contractors who are well-versed in electrification, solar,​ and efficiency. Contractors who earn the Badge have completed a series of 5 training modules, as well as continuing education for badge maintenance. You can search for “Electrification” in the Contractor Locator, or else search for the type of contractor you are looking for, and look for the badge by their name. Learn more about the Michigan Saves ​home electrification program on their Residential Electrification webpage​.​​

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