Heating and Cooling

The majority of residential and commercial energy consumption is used for heating and cooling. Most heating and cooling energy can be saved through better equipment, compact buildings with shared walls, and more efficient energy sources such as a district heating and cooling system.

Energy Savings Potential

The following portrays the potential for selected tools to save energy on heating and cooling. The savings from housing forms (attached housing and apartments) portray savings relative to detached houses.

Sources: Adaptive thermal comfort from Barbadilla-Martín et al. ¹, personal comfort devices from Carmichael et al. ², emerging HVAC technology from Goetzler et al. ³, non-vapor cooling from Goetzler et al. ⁴, building envelopes from the IEA ⁵, passive cooling from Kamal ⁶, district heating and cooling from Lubinski ⁷ and Stellar Energy ⁸, smart thermostats from Nest Labs ⁹, and solar cooling from the UN Environment Programme ¹⁰. Additional information on thermal comfort available from Yang et al. ¹¹. Energy savings for apartments and attached housing is estimated from the Residential Energy Consumption Survey ¹². Upgrades to building envelopes should save cooling energy as well as heating energy, but we lack reliable estimates on the magnitude of savings.

Heating Source

The following portrays the energy, economic, and environmental characteristics of heating fuel options for space heating, water heating, cooking, and clothes drying for a typical new home.

Data sources: Brennan ¹³ for coal, the Committee on Climate Change ¹⁴ for hydrogen, Fischer and Madani ¹⁵ for geothermal and air-source heat pumps, Lubinski ⁷ and Werner ¹⁶ for district heating, the Department of Energy ¹⁷ for wood, Vineyard et al. ¹⁸ for gas heat pumps, and the remaining heat sources from the American Gas Association ¹⁹. Additionally, the AGA is used to estimate the heating energy demand for a typical new home. Data from the EPA ²⁰ is used to estimate emissions factors. For electricity-based heating sources, emissions factors and primary energy are based on the average US electricity mix in 2018. The energy and environmental performance of a district heating system is highly dependent on the energy source. The primary energy estimate for district heating is based on European Union standards ⁷ and the greenhouse gas estimate from world performance ¹⁶.

Air-source heat pumps work best in moderate climates, and the high performance figures might not be achievable in cold climates ²¹.

Despite the current enthusiasm for heat humps, the technology struggled to retain market share in the 2010s.

Source: ²².

Heating Efficiency

Even if a common fuel source is used, such as electricity, efficiencies between different heating systems can vary significantly, such as between heat pumps and electric resistance heating. Construction codes that mandate higher efficiency options can be good investments.

Refrigeration

Under the Montreal Protocol, the widely used chlorofluorocarbons (CFC) refrigerant, which contributes heavily to ozone depletion, was phased out. Their replacements, hydrochlorofluorocarbons (HCFC) and hydrofluorocarbons (HFC) also contribute more than expected to ozone depletion, and are potent greenhouse gases, and they are being phased out. There is an estimated 91 billion tons CO₂-equivalent, a bit more than two years of world emissions, greenhouse gas savings potential estimated by better management of HFCs and HCFCs ²³.