Plant in Sweden was an early example of nuclear cogeneration, providing small quantities of both heat and electricity to a suburb of the country's capital between 1964 and 1974. The Beznau Nuclear Power Plant in Switzerland has been generating electricity since 1969 and supplying district heating since 1984. The Haiyang Nuclear Power Plant in China started operating in 2018 and started supplying small scale heat to the Haiyang city area in 2020. By November 2022, the plant used 345 MW-thermal effect to heat 200,000 homes, replacing 12 coal heating plants. Recent years have seen renewed interest in small modular reactors (SMRs) and their potential to supply district heating. Speaking on the Energy Impact Center's (EIC) podcast, Titans of Nuclear, principal engineer at GE Hitachi Nuclear Energy Christer Dahlgren noted that district heating could be the impetus for the construction of new nuclear power plants in the future. EIC's own open-source SMR blueprint design, OPEN100, could be incorporated into a district heating system. Natural underground heat History Geothermal district heating was used in Pompeii, and in Chaudes-Aigues since the 14th Century. United States Direct use geothermal district heating systems, which tap geothermal reservoirs and distribute the hot water to multiple buildings for a variety of uses, are uncommon in the United States, but have existed in America for over a century. In 1890, the first wells were drilled to access a hot water resource outside of Boise, Idaho. In 1892, after routing the water to homes and businesses in the area via a wooden pipeline, the first geothermal district heating system was created. As of a 2007 study, there were 22 geothermal district heating systems (GDHS) in the United States. As of 2010, two of those systems have shut down. The table below describes the 20 GDHS currently operational in America. Solar heat Use of solar heat for district heating has been increasing in Denmark and Germany in recent years. The systems usually include interseasonal thermal energy storage for a consistent heat output day to day and between summer and winter. Good examples are in Vojens at 50 MW, Dronninglund at 27 MW and Marstal at 13 MW in Denmark. These systems have been incrementally expanded to supply 10% to 40% of their villages' annual space heating needs. The solar-thermal panels are ground-mounted in fields. The heat storage is pit storage, borehole cluster and the traditional water tank. In Alberta, Canada