Oil or petroleum was once a key player in the electricity sector, but now it is used only marginally, usually as back-up reserve in diesel generators for major consumers, such as factories, hospitals, airports or as an electricity source in islands (for example in Greece).

Oil lost its share because of price, it is far more expensive to burn oil than burning coal or gas.

Merits of oil include high energy density, easy to transport and very stable composition, remaining liquid in most climatic conditions. Drawbacks of oil are price are environmental concerns (Webber, 2014).