A man stands in front of a heat pump designed to capture and recycle energy from the sewer.
Dieter Nagl

Robert Simmer, director of Stadtwerke Amstetten, a local utility company in Austria, stands in front of a heat pump designed to capture and recycle energy from the sewer.

High-Efficiency Heat Pumps

Reduce SourcesElectricityEnhance Efficiency
Reduce SourcesBuildingsShift Energy Sources
CO2 Equivalent
Reduced / Sequestered
Billion $US
Net First Cost
(To Implement Solution)
Trillion $US
Lifetime Net
Operational Savings
Heat pumps extract heat from the air and transfer it—from indoors out for cooling, or from outdoors in for heating. With high efficiency, they can dramatically lower building energy use.

Solution Summary*

The building sector worldwide uses approximately 32 percent of all energy generated; more than one-third of that is for heating and cooling. Maximum efficiency in heating and cooling could cut energy use by 30 to 40 percent.

The means to increase efficiency are at hand, and one technology stands out from the rest: heat pumps. Like a refrigerator, a heat pump has a compressor, condenser, expansion valve, and evaporator, and transfers heat from a cold space to a hot one. In winter, that means pulling heat from outside and sending it into a building. In summer, heat is pulled from inside and sent out. The source or sink of heat can be the ground, air, or water.

While cost can be high and efficiency fluctuates depending on local climate, heat pumps are easy to adopt, well understood, and already in use around the world. They can supply indoor heating, cooling, and hot water—all from one integrated unit. When paired with renewable energy sources and building structures designed for efficiency, heat pumps could eliminate almost all emissions from heating and cooling.

* excerpted from the book, Drawdown

Heating and cooling of residential and commercial building space requires more than 13,000 terawatt-hours of energy and is estimated to increase to more than 18,000 terawatt-hours by 2050. This energy use comes from on-site fuel combustion and electricity-based systems—from gas furnaces to air-conditioning units. High-efficiency heat pumps reduce fuel consumption to zero and use less electricity to generate heating and cooling. Current adoption is low at 3 percent of delivered heat, but we estimate rapid growth to 20–40 percent in 2050 as costs continue to decrease. For a cost of US$78–120 billion above what would be spent on conventional technologies, operating savings could reach US$1.1–2.5 trillion over the technology’s lifetime. Emissions reductions in this scenario come to 4.2–9.3 gigatons of carbon dioxide.

Note: August 2021 corrections appear in boldface.