The generation of electricity is the same as the conversion of energy. This means that the energy contained in a fossil fuel is first converted into thermal and physical energy and then finally into electrical energy. This process takes place in the power plant. Unfortunately, energy is lost at each stage of the conversion. According to laws of physics this means that out of 100 percent of the chemically bonded energy in, for example, natural gas only approx. 58 percent can be converted into electrical energy, and therefore into electricity. The 58 percent approximate degree of efficiency that is attained in Irsching 5 is a very high level according to the current state of technology.

The conversion of energy is described in physics in the Carnot process. The Carnot process enables the conversion of fuel energy into heat and then into mechanical energy in a water-stream cycle. Together with the gas turbine, this results in a level of efficiency of 58 percent, which is very difficult to increase. The Siemens AG and the E.ON Kraftwerke GmbH are currently on the brink of a major breakthrough at Irsching 4. After years of development work, Siemens has succeeded in constructing the highest performing gas turbine in the world. This turbine will attain an unrivalled level of efficiency of over 60 percent in the combined operation of gas and steam.

Incidentally, there is a difference between efficiency and degree of utilization. The degree of efficiency describes the ability to generate electricity. If waste heat can be used to combine heat and power in the power plant then one is referring to the degree of utilization. Therefore the degree of utilization is always greater than the degree of efficiency.