Space Heating

Heating your building is the most common use of heat pumps. Because heat pumps transfer heat, not create heat, they are significantly more efficient than traditional electric resistance heat that is used with baseboards or electric boilers. In Juneau, heat pumps are commonly 2.5 to more than 3 times more efficient than traditional electric resistance over a heating season. Compared to heating oil, wood, and electric resistance, heat pumps will provide significant discounts to your heating bills, depending on the cost of fuels. Heat pumps for space heating in homes and other small buildings can be air source or ground source.

Efficiency and Cost

The high efficiency of heat pumps allows for your building to be heated at low cost, compared to electric resistance as well as fuel oil, biomass and propane. For every unit of electrical energy you purchase to power a heat pump, 2 to 3 units of heat energy are delivered into your building, averaged across seasons. When calculated in absolute heat energy terms, air source heat pumps cost 50 to 60% less than fuel oil, propane, wood pellets or electric resistance to provide the same amount of heat. With large enough energy savings, the heat pump can pay for itself.

Distributing Heat

Heat Pumps have four main ways to distribute heat throughout a building: ductless systems, ducted systems, mini ducted systems and hot water systems.

  • Ductless heat pumps connect the exterior heat collection units with the interior heat distribution units. There can be a single distribution unit in your main living space, or there can be multiple interior distribution units spaced throughout a building.
  • Ductless systems are most cost effective when delivering heat to open, main areas of a building. Costs rise quickly when attempting to meet the heating needs of hard to reach rooms. Consider combining a heat pump in the main living space with an electric boiler or electric furnace providing heat to hard to reach rooms.
  • Refrigerant lines run between the exterior and interior units, which brings heat from the outdoors into your building.
  • Moving heat with ducts create efficiency losses, so ductless units are generally more efficient than ducted units.
  • Ductless units usually have the lowest upfront cost of all options.
  • Ductless systems only work with air source heat pumps.
  • Ducted systems distribute heat through a building’s duct work. Using a furnace-like unit, heat from the exterior is released in a central heating unit, and distributed throughout a building with fans.
  • Ducted systems experience heating losses as the heating travels through the ducts to the building’s rooms and are less efficient than ductless systems.
  • Installing duct work upfront can quickly make a ducted system uneconomical. Ducted systems work best when duct work already exists from a pre-existing heating system or in new construction.
  • Because ducting is designed to meet all of a building’s room’s heating demands, there are no substantial increased costs of providing heat to hard to reach rooms.
  • Ducted systems can work with air source or ground source heat pumps.
Mini Ducts

Mini ducts, or short ducted mini split systems, use small indoor low-pressure fan coils with short ducts to serve multiple small rooms. These types of systems can be an alternative to multi-head systems, and are particularly useful in situations where multiple rooms, removed from the main open space of a home, need to be served.

A common issue homeowners run into when considering a whole-house heat pump retrofit is providing code-compliant heating to backrooms such as bedroom. Miniducts are a possible solution to this. An alternative is a two system heating system which uses a heat pump in the main living space combined with a electrified legacy system (boiler or furnace) which solely heats the back rooms. Homeowners considering a whole-house retrofit should weigh the financial costs of these two options.

Hot Water
  • Ground source heat pumps can provide heat to water, which can then heat your building using hot water baseboards or in floor radiant heating. .
  • Because ground source heat pumps are more efficient than air source heat pumps, hot water systems which can only be used with ground source heat pumps are generally more efficient.
  • However, higher front costs for both new construction and retrofits make hot water systems generally less economical than ductless systems.
  • Most houses with hot water baseboard are not compatible with GSHPs or air to water heat pumps because the temperature of the water produced by heat pumps is much lower than that of boilers.  Significant modification of the hydronic distribution system may be required to convert it to a water heat pump system.
  • One significant advantage of GSHPs and AWHPs is that they are able to perform double duty, heating the space as well as heating domestic hot water.  ASHPs are not capable of that.