Wuerzburg as a German Franconian city with more than 130,000 inhabitants and a University with more than 30,000 students has always emphasized the importance of a municipal energy solution. Hence a cogeneration plant was built in 1954 serving both electricity and heating. The choice of fuel was coal due to the resource situation at that time. The most advanced and efficient technique back then was the use of steam as medium for heat transportation through the grid in the Wuerzburg inner city. With the liberalisation of the energy market and the rising sensitivity for climate issues, Wuerzburg has been seeking a sustainable opportunity modernising the coal based cogeneration plant in 2003. The choice of technology for this modernization of the plant fell on a cogeneration based on gas.