BEWAG's business is to supply the city of Berlin with electric power.
If BEWAG would do this through exclusive use of condensation power stations, primary energies fed into the system would be utilized with a yield of only about 38%.
These considerable losses are unavoidable, subject to physical-technical laws:
The turbines generating electric power are driven by steam that has to be condensed "after use". This process calls for large amounts of water to cool the steam - to avoid damage to the natural environment the tempature of this water must not exceed 28 degrees Celsius. This temperature is too low, however, to heat the water circulating through the District Heating pipelines. Therefore part of the steam in the electric power turbines is drawn off in order to generate the heat for the District Heating System. Hence District Heating is by no means a mere recycling of waste, rather it is the perfect complement to the process of electric power generation requiring such considerable energy inputs.
Yet another comparison speaks in favour of co-generation: in this system of power production at the most 50 per cent of primary energy is required to produce 100 per cent of usable heat. In contrast to that, oil-burning installations commonly used everywhere have to be fired with about 110 to 130 per cent of fuel input - depending on their specific efficiency - for every 100 per cent of usable heat.