Heat Pump Systems

How do heat pump systems work?

Put simply, they pump heat from one place to another! This may come as a surprise, but there are heat pumps all around us. One such example of a “heat pump” we use every day is the humble refrigerator. Instead of “creating cold,” a fridge actually pulls heat from the air and objects inside of it, and pumps that heat to the outside of the fridge.

When talking about heating and cooling equipment, a heat pump does the exact same thing – it uses the refrigeration cycle to move heat from one place to another. In the home, this means pumping heat out of the house in summer, and pumping heat into the house in winter. If the first part of that scenario sounds familiar it’s because it is! What we call air conditioners are technically heat pumps that only work in one direction.

Heat pump diagram
Heat pump graphic

Why heat pumps?

It is much more efficient to move heat than it is to generate it. A traditional furnace or boiler burns fuel to generate heat, and because there is energy lost generating this heat, they can never be 100% efficient. Heat pumps on the other hand can be upwards of 300%–400% efficient because they move heat instead of generating it. This means that for every unit of energy they use, they produce three to four units of heat.

Though heat pump efficiencies do drop as the weather gets colder, they’re still often well over 100% efficient. Further, these systems have improved in recent years, and continue to improve every year. They can now function in below freezing temperatures and for this reason, they are becoming a viable option for many homes. They offer substantial energy savings and, in many cases, can deliver energy bill savings as well.



A ductless heat pump, also known as a mini-split, provides heating and cooling without requiring ductwork. These units provide flexibility and are a great solution for bonus rooms and expansions, hot and cold spots in the home, and homes without existing ductwork. If enough are installed, they can fully replace an existing HVAC system, though more often they’re installed to augment existing systems.

Ductless heat pumps are often installed in a one-to-one setup, with a single outdoor unit connected to a single indoor, or head, unit. The head units are typically mounted on the wall, but can also be floor-mounted, in-wall units, or in-ceiling cassettes with smaller ducts leading to multiple rooms.

Most systems can also be installed in multi-split setups as well, with a single outdoor unit supplying multiple indoor units.


A ducted heat pump functions like a ductless heat pump, but the outdoor unit replaces the traditional air conditioner outside and connects to the indoor ductwork through the air handler. This air hander unit can be a fully-electric system with an electric furnace as back-up, or a hybrid system with a fossil fuel furnace as back-up – this second type is also called a dual-fuel system and is described further below.

Ducted heat pumps typically have a large outdoor unit and are meant to offset a sizable portion of the heating and cooling load of the home. The size of the heat pump installed is often limited by the size of the existing ductwork in the home, however – a limitation not shared by its ductless counterparts.


In some cases, heat pumps provide all a home’s heating and cooling with electricity, but some homeowners have opted for a dual-fuel heat pump. This is not a different type of heat pump, but a mix of heating equipment using different fuel sources, more specifically a ducted heat pump—which is electric—being paired with a gas or propane furnace. In these configurations, the heat pump provides the primary heating, and the furnace serves as a back-up. A dual-fuel heat-pump could be a good investment for your home if your air conditioning system needs replacement or is inefficient, but your furnace is still in working order. This allows you to take advantage of cost savings from both technologies: efficient heating from your heat pump in mild temperatures as well as cheaper natural gas from your furnace on the coldest days of the year.

Focus on Dual Fuel Heat Pumps - Video
Cold Climate

Finally, there are cold climate heat pumps. Their name refers to their ability to operate more efficiently at low outdoor temperatures than standard air source heat pumps. Cold climate heat pumps have a variable speed inverter-drive compressor allowing the unit to continue providing efficient heat in freezing temperatures. Both ducted and ductless heat pumps can be cold climate heat pumps.

Geothermal Heat Pumps

Also known as ground source heat pumps, these systems use the relatively constant temperature of the ground to heat and cool your home. Instead of using the air around the outdoor unit, geothermal heat pumps use liquid-filled pipes buried in the ground to utilize heat stored in the Earth. Just like air source heat pumps, these come in various configurations including horizontal or vertical, closed-loop or open-loop, pond/lake, and hybrid systems.

Due to higher installation and material costs, geothermal heat pumps cost more than other heat pumps. However, these are a smart investment as they can last longer than 50 years.

Other Heat Pumps
Future of Heat Pumps

Heat pumps are a fascinating spectrum of technology with lots of future potential. Other heat pump types you may hear about include air-to-water, water source, and gas absorption heat pumps. See the research section below for more information on these emerging technologies.


Want a heat pump for your home?

Energy experts recommend insulating and air sealing your home as the first step to saving money on energy. (Source: ACEEE)
This allows you to:

  • Appropriately size your heat pump when it is installed.
  • Ensure it can keep your home warm on the coldest days.
  • Reduce the cost of using electricity, a more expensive energy source.
Not sure if your home insulation is efficient?
Start with a Home Energy Assessment
residential neighborhood

Unsure of which heat pump is right for you?

Check out the Electric Heat Pump Customer Buying & Operation Guide for Single Family Homes by selecting the link below.

Heat Pump Guide Find a Trade Ally Find a Rebate


Focus on Energy Research

Though heat pumps are new to Wisconsin, they aren’t a new technology. Focus on Energy has supported several research projects to explore the feasibility and implications of heat pumps in the state. See what we’ve learned.

Single-Family & Multifamily Air Source Heat Pumps (ASHP)

Final Report (October 2021) Presentation (September 21, 2021) Presentation Slide Deck Ductless Mini-Split Heat Pump Market Assessment and Savings Review Report Air to Water Heat Pump and Gas-Absorption Heat Pump Research
National Resources

Check out these leading national organizations for more heat pump information.

Air-Source Heat Pumps | Department of Energy Air-Source Heat Pumps | ENERGY STAR Frequently Asked Questions About Heat Pumps | EnergySage Geothermal Heat Pumps | Department of Energy Geothermal Heat Pumps | ENERGY STAR

Heat Pump Buying and Operation Guide

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