A flexible plant makes it possible to balance the supply of energy on the grid. Flexible cogeneration plants can be approached in three different ways on the market: proactively, by adapting energy output and market prices; based on the so-called “active balancing” approach, or taking active action to balance the supply of energy on the grid; and last but not least, in a reactive way, coping with market prices. De Keyser illustrates an application case of the active approach, the Elias pilot project.