By Isabella Kaminski

E.ON claims that the project, which was launched in Hamburg, is unique in Europe.

Home owners producing heat from solar-thermal systems will be able to feed it into E.ON Hanse Wärme’s energy grid. Customers own the heat they supply to the grid, so they can feed in heat during the summer and withdraw it again in colder months – meaning that home storage units are not necessary.

The German Federal Ministry of the Environment is contributing to the funding of the €7 million (£6.2m) project. For the purposes of this pilot project a housing estate in Eastern Hamburg was converted into a multi-function storage system and integrated into the E.ON district heating grid.

Dr Dierk Paskert, Member of the E.ON Energie Board of Management and Chairman of the E.ON Hanse Supervisory Board, says: "The combination of point-of-use production and central storage will be an essential element of tomorrow’s energy supply. With this project E.ON is showing that it is already possible not only to feed renewable power into the grid but also heat.”