A 'heat network' is a district heating scheme which comprises a network of insulated pipes used to deliver heat, in the form of hot water or steam, from the point of generation to an end user and provide a means to transport heat efficiently. Networks vary in size and length, carrying heat just a few hundred metres between homes and flats, to several kilometres supplying entire communities and industrial areas. The distance a network can reach is also easily extended by simply adding more providers of heat, or 'heat sources', along the way.