Engine manufacturers generally require the use of diesel fuel in accordance with DIN EN 590 for the operation of their emergency power systems. To comply with the Biofuel Quota Act, up to 7% biodiesel is now commonly blended with diesel fuel. With its special properties, this fuel quality is designed for the transport sector and for use within 90 days, but not for long-term storage. In the case of biogenic blends, longer storage periods for diesel stocks increase the risk of fuel-related malfunctions of the emergency power system due to degradation and microbiological infestation.

Alternatively, it is also possible to use low-sulfur heating oil according to DIN 51603-1. It has the same physicochemical properties as diesel but does not contain any biodiesel. Since emergency power systems are stationary engines, the use of heating oil is permitted by law. Another advantage of using heating oil is the lower cost due to the lower energy tax of 6.14 cents per kilogram compared to 47.04 cents per liter for diesel fuel. Before deciding to use heating oil, it is essential to check whether the manufacturer of the system has given approval for its use.