Heat Pumps

Why Heat Pumps?

Heating and cooling account for almost half of the energy use in a typical U.S. home. Heat pumps offer an opportunity to reduce energy costs, and at the same time reduce greenhouse gas (GHG) emissions.

How do they work?

Air-source heat pumps provide heat by extracting heat from outside air and delivering it indoors as needed. Because they are moving heat, rather than generating it through combustion or resistance, heat pumps can achieve efficiencies well above 100%. Long used for cooling in warm climates, heat pumps are now able to provide efficient heating in cold climates even at outdoor temperatures as low as -15 °F.

Air-source heat pumps are capable of not only heating in the winter (by extracting heat from outside air) but also cooling in the summer (by extracting cold from outside air.) Heat pumps use the same technology as your refrigerator or air conditioner.

Ground-source heat pumps, sometimes referred to as “geo-thermal” work just like air-source, except they extract the heat and cold from water pumped through the ground, which stays at roughly the same temperature all year-round.

Most heat pumps are "ductless," meaning they don't require bulky and expensive air ducts. Rather, they consist of an outdoor unit connected to indoor air handlers by refrigerant lines, which carry heat between the two units. There are four types of indoor units:

1) Wall units
2) Floor units
3) Ceiling cassettes
4) Mini-Ducts

Why get a high-efficiency model?

If you're considering heating your home or business with a ductless heat pump, make sure to install a high efficiency model. Compared to standard efficiency ductless heat pumps, high efficiency units have lower operating costs and provide more heat at lower temperatures.

What are the advantages?
  • Low-cost heat - Heat pumps are one of the lowest cost sources of heat at current energy prices. Click here to compare heating costs of different heating systems.
  • Comfort - With advances in controls, heat pumps can maintain very constant temperatures.
  • Safety - Because heat pumps are electrically powered, there is no risk of combustion gas leaks.
  • Air quality - Heat pumps filter indoor air all year and dehumidify it in the summer, improving air quality.
  • Room-by-room control - When installed with multiple indoor units, heat pumps allow for room-by-room temperature control.
  • Low-cost air conditioning - Today’s best heat pumps are twice as efficient as typical air conditioners.
What are other considerations?
  • Cold temperature performance - Because heat pumps extract heat from outside to provide warm air inside during the heating season, as it gets colder outside, the heat pump must work harder to keep up, making them less efficient. For example, a unit that delivers four units of heat for every unit of electricity at 50°F, may only deliver two units of heat for every unit of electricity at temperatures below zero. There is evidence of the highest performance units operating and providing heat even below -15°F in Presque Isle. But if the temperature drops low enough, the system may turn off completely. Be sure to check out the lower operating temperature listed for your heat pump. If you experience prolonged periods below that temperature, consider a secondary backup heating system to maintain your desired comfort level through the chilliest nights. If you use a backup system, just be sure to switch back to your heat pump once temperatures rise, or you could quickly lose your savings.
  • Air movement - Heat pumps circulate air to heat and cool spaces. This is nice for cooling but can cause cooling sensations while the heat pump is heating. Take a look at Efficiency Maine’s ductless heat pump user tips to learn the recommended fan settings for the heating and cooling season.
  • Heat distribution - Ductless heat pumps rely on air movement to move heat out into a room. This can make it hard to get heat around corners and into dead-ends. Take a look at our ductless heat pump user tips [link to below] and installation considerations [link to below] to learn how to get the most from a heat pump.
  • Interactions with the primary heating system - If you are thinking about using a heat pump as a supplementary heating system, make sure to locate it in an area where it won’t interact with the thermostat for the central system: that could result in your primary system shutting off your heat pump or your heat pump shutting off your primary system. This is not a concern if you are using a heat pump as your primary heating system. Take a look at our ductless heat pump installation considerations [link to below] to learn where to install your heat pump.

Ductless Heat Pump Installation Considerations

It's important to know up front what you're looking to get from your heat pump. Some common reasons people switch to heat pumps are cost savings, comfort, reduced environmental impact, convenience, and aesthetics. Be sure to share your goals with your installer. It'’s also helpful to know if the heat pump will be the only heating system, the primary system, or a supplemental system.


The primary drivers of heat pump costs are the number of indoor units installed and the complexity of installation. Costs can be reduced by maximizing the space that each indoor unit heats and cools, as well as by selecting locations that are easy for installers to access.

Indoor unit location
  • Heat rises - while an indoor unit might deliver some heat to the floor above, it won’t send any heat to the floor below. Likewise, cool air from a first floor unit in air conditioning mode will not cool any floors above it.
  • Air flow is tough to predict and every building is different. In general, open spaces tend to be easy to heat and cool from one indoor unit, while it can be challenging for heat to go through a doorway. In addition, a room with a door that is typically closed will not benefit from a heat pump located outside the room.
  • The interaction with existing thermostats can be tricky. If an existing thermostat (for example, for a boiler) is going to end up in a space heated by a heat pump, then that boiler thermostat will never fall below its setpoint and will never ask for heat. As a result, other areas served by the same zone (such as bedrooms served by the boiler but not by the heat pump) may become cooler than desired. If you are not adding multiple heat pumps to cover the entire boiler zone, consider moving the boiler thermostat to another part of the boiler zone during your heat pump installation.
Indoor unit types

There are four types of indoor units:

  • Wall units are by far the most popular. They are the most efficient and, because they are mounted high on a wall, they can heat or cool a large area. That said, they are also the most noticeable.
  • Floor units are mounted on the wall down by the floor. They are less conspicuous, but are not as efficient and their airflow can be obstructed by furniture.
  • Ceiling cassettes are mounted above the ceiling and only their vents can be seen. They are nearly invisible, but are less efficient and may not be able to distribute warm and cool air as far as a wall unit. These are typically installed in attic floors or above suspended ceilings.
  • "Ducted ductless" indoor units are ceiling cassettes that connect rooms. The most common configuration is a vent in a hallway ceiling that takes in air, and 2 to 3 ceiling vents that supply warm and cool air to adjoining rooms.

Outdoor unit locations

Ductless heat pump outdoor units can be up to 60 feet away from their indoor units, so there's a lot of flexibility as to where they are installed. Here are some considerations:

  • Aesthetics - This consideration is highly personal but important. It can take a while to get used to seeing a heat pump, especially at first. Careful planning can minimize the visual impact of your outdoor unit.
  • Unobstructed airflow - Although it's tempting to tuck units into tight places for aesthetic reasons, it's important to remember that they heat and cool based on outdoor air. The more access they get, the better they’ll work. Avoid shrubs, places prone to snow drifts, and structures that may block airflow.
  • Door/window/walkway interference - It’s best to avoid installing the outdoor unit where it could interfere with the operation of a door or window. In addition, outdoor units release water when they defrost in the winter, which can form icy patches. Be sure to pick a spot where that won’t be an issue.
  • Roof runoff - If the outdoor unit is going to be installed under a roof drip line, then be sure the unit is equipped with a rain cap.
  • Serviceability - Keep in mind ease of service when selecting an installation location.

Line sets - Indoor units are connected with outdoor units by two insulated copper pipes and one wire. It’s easiest to hide them in a closet, basement ceiling, attic floor, or outside wall, but sometimes they can be hidden in a wall. These decisions affect both costs and aesthetics.

Condensate drain line - When heat pumps are in air conditioning or dehumidification mode, they produce condensate. This water needs to be drained, such as to a garden or downspout.

Code Requirements - As with most residential and commercial equipment installations, it’s best to consult with your installer to ensure code compliance. These requirements may impact installation costs.

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People's Action for Clean Energy (PACE)
PO Box 134
West Simsbury, CT 06092
(860) 217-3686