4G Heat Networks represent a quantum leap in terms of localised energy generation, distribution, and storage. 

Taking forward the 3G model of hot water systems tied to the heat sources as initially specified, 4G Networks are planned to encompass multiple buildings and can incorporate renewable energy sources, either at the initial design stage or in future. 

Further 4G characteristics are high standards of insulation, lowest workable temperatures for water supply & return and the provision of energy retention, either by thermal storage, batteries, or gas conversion. 

To optimise 4G operations, sufficient metering should be deployed, to allow minute-by-minute decision-taking by central control.