The Hype Over Ductless Isn't Just Hot Air
November 17, 2012

One of the hottest selling items in the City of Bainbridge Island, WA is a mini split.  No, it is not some new fashion statement.

A mini split, also known as a ductless heat pump, heats and cools buildings of all types in ways that save money and increase comfort.  A heat pump system's ability to heat and cool is particularly handy here in the Northwest because purchasing a separate air-conditioning system to maintain the chill for just five to 10 uncomfortably hot days each summer is a bit frivolous.

Efficiency improvements like mini splits lack the sex appeal of distributed renewables like rooftop solar, yet they can make a significant impact, often saving much more energy than the energy that would be produced by a similar investment in solar panels.

Mini split systems gained traction on Bainbridge Island due to RePower Bainbridge, an organization committed to creating a more sustainable community through energy assessments, cash-back incentives, energy-efficiency financing, and a network of skilled contractors. RePower took on the challenge of making efficiency desirable and succeeded. (Bainbridge Island's achievements in reducing demand for electricity citywide are detailed in New Energy Cities' report Powering the New Energy Future from the Ground Up: Profiles in City-Led Clean Energy Innovation.)

RePower Bainbridge was smart to focus on promoting heat pumps because they are a sound option in moderate climates such as the Northwest's, which rarely require extreme heating or cooling. A ductless heat pump is similar to other air-source heat pumps in that it consists of an outdoor compressor/condenser and an indoor air-handling unit.

Electric resistance heating, the traditional choice for electricity-powered systems, converts nearly 100 percent of the energy in the electricity to heat. This sounds like great efficiency, but compare: heat pumps use electricity only to power a system that moves heat from a cool space into a warm one. This makes the cool space cooler and the warm space warmer, much like a refrigerator.

Because they simply transport existing heat rather than heating cool air, heat pumps can work with well over 100 percent efficiency. (This means that more heat energy heats the target space than is used in operating the space conditioning system.)

Ductless, mini-split-system heat pumps are also a good retrofit option for homes with "non-ducted" systems such as baseboard heating, cable ceiling heat, or radiant panels. They also work well for projects such as room additions, where extending existing distribution ductwork is not practical or worthwhile.

Here are the reasons to consider going ductless:

  • A ductless system can provide even more efficiency than a standard air-source heat pump, for two reasons:
    1. It avoids duct losses of heat, which can account for as much as 30 percent of heating energy use, especially when ducts run through unconditioned spaces.
    2. It is split into zones, each with its own air-handling unit and thermostat, which allow residents to condition only the rooms they are in.
  • Installation is quick and simple, which means you can significantly upgrade your home's energy efficiency without much disruption. In general, the conduit that connects the indoor and outdoor components requires only a three-inch hole through a wall. Depending on where the indoor unit is placed, a minor retrofit may be necessary.
  • Ductless heat pumps offer comfort and control that isn't possible with other systems. Different zones can be set to different temperatures, making ductless systems ideal for multifamily housing and multi-use buildings. An ultra-quiet fan in each zone eliminates hot and cold spots within rooms by evenly circulating conditioned air.
  • Customers installing mini splits have flexibility in design, both interior and exterior, that isn't available when installing other types of heating. The compressor can sit as distant as 50 feet from the indoor air handler to heat and cool rooms on the front side of a building with the outdoor unit in a less obtrusive or noticeable place. The indoor piece can hang from the ceiling, stand on the floor, mount flush into a drop ceiling, or sit on a wall. Many come with a remote control, which expands positioning options even further.
  • Because split-systems only entail a small hole in the wall, they can also make a home or business a little safer than traditional heating and cooling options. Through-the-wall and window-mounted room air-conditioners can be an entrance for intruders.

Perhaps most importantly, switching to a ductless heat pump system can save money in several ways:

  1. Installation costs less thanks to the simplicity of the system.
  2. Here in the Pacific Northwest we have inexpensive electricity, which renders super-efficient electric heating systems a very cost-effective choice
  3. Many utilities will also give you cash just for installing a ductless heat pump

Puget Sound Energy, Idaho Power, Seattle City Light, Snohomish County PUD No. 1, Clark Public Utilities, and nearly every other Northwest utility offer rebates for switching to a ductless system. These incentives are part of the NW Ductless Heat Pump Project, an initiative of the Northwest Energy Efficiency Alliance (NEEA) that develops market capacity and creates a regional organizational infrastructure for inverter-driven ductless heating and cooling systems in existing single-family homes. Their website,, features a catalog of utility incentives in Oregon, Washington, Idaho, Montana, and Wyoming.

Alexis Allen, manager of the NW Ductless Heat Pump Project, estimated that "we have roughly about a million homes that this technology is applicable for in the Northwest. If we can capture that, that's about 440 average megawatts of savings." National Public Radio's Pacific Northwest Regional Correspondent Tom Banse equated that savings to one medium-sized coal-fired power plant in a May 25, 2010 story on ductless heat pumps that focused on Bainbridge.


Sign up for Climate Solutions updates!