An apparatus for prediction of the residual lifetime of an electrical system includes: an input unit; a processing unit; and an output unit. The input unit provides at least one sensor data from at least one sensor to the processing unit, the at least one sensor data including a measurement of at least one physical parameter of at least one component of an electrical system. Each sensor data is associated with a corresponding sensor and relates to a measurement of one physical parameter of a corresponding component of the electrical system. Each sensor data extends over a plurality of time windows and is assigned to a certain data class, such that sensor data at a particular time window has a value that falls into one of the data classes. For each sensor data the processing unit assigns the sensor data at each time window into a corresponding measurement window.