Energy-efficient and low/zero-carbon heating and cooling systems improve energy savings and play a central role in reducing CO2 emissions and increasing system flexibility. The reduced oil and gas consumption as the result of a switch to these technologies improves energy security and may also improve a country’s balance of payments by reducing imports of energy. Examples of energy-efficient and low/zero-carbon heating and cooling technologies may include: • District heating is an underground infrastructure asset where thermal energy is provided to multiple buildings from a central energy plant or plants. Steam or hot water produced at the plant is transmitted 24/7 through highly insulated underground thermal piping networks. The thermal energy is transferred to the building’s heating system, avoiding the need for boilers in individual buildings including commercial, industrial, and residential. • District cooling is a modern, efficient way to air condition a network of buildings in cities or campuses. Central cooling plants house large, highly efficient, industrial-grade equipment that produces chilled water for supply to customer buildings through an insulated underground piping network. Cold supply water enters the building and flows through a heat exchanger, absorbing heat from the building space before recirculating back to the central plant through a closed loop return line. • Active solar thermal (AST) can provide space and water heating, as well as cooling needs. • Combined heat and power (CHP): Traditional CHP systems are mature and a useful transitional technology, while micro-CHP, biomass CHP and even fuel cell systems (using CO2-free hydrogen) may emerge as an important abatement option. • Heat pumps for cooling and space and water heating are mature, highly efficient technologies that take advantage of renewable energy. • Thermal storage can maximize the energy savings and energy efficiency potential of other technologies, facilitate the use of renewables and waste heat, and improve flexibility. • Digitalization and smart controls can encourage energy-efficient consumer behavior, by making use of the increasing quantity of building energy data available; additionally, real-time pricing and dynamic communication with smart energy networks will enable the building sector to provide very cost-effectively some of the increased flexibility required to accommodate an increased share of variable renewables, helping to reduce the need for expensive electricity storage.