A computer implemented error-based method for calculating a remaining useful life of an apparatus comprising the following method steps (21, 22, 23, 24): - providing acquired time-series of previous runs of the apparatus containing data of a plurality of sensors of the apparatus and acquiring a time series containing data of the sensors with respect to a current run of the apparatus, wherein each sensor is configured to monitor a parameter of the apparatus or a parameter of an environment of the apparatus, respectively, wherein cumulative counts of errors occurring during a run of the apparatus are calculated for each type of an error and provided within the time series, wherein an error occurs when a parameter monitored by a sensor breaches a pre-defined threshold, wherein a linearly decreasing remaining useful life for each previous run of the apparatus indicating breakdowns of the apparatus by a value of zero is calculated and provided within the time series, - mapping the breakdowns of the apparatus as points in an error space, wherein each dimension of the error space refers to one type of an error, respectively, wherein the breakdown points are mapped at coordinates (42, 43) which represent cumulative error counts at the time of the breakdowns, - mapping a test point in the error space, wherein the test point represents cumulative error counts for the apparatus in operation, - identifying at least two nearest breakdown points with respect to the test point by calculating and comparing distances of the test point to all breakdown points mapped in error space, - calculating the remaining useful life of the apparatus which is a function of a quotient of a distance of the test point to an origin of the error space and a mean distance of the at least two nearest breakdown points to the origin. - providing acquired time-series of previous runs of the apparatus containing data of a plurality of sensors of the apparatus and acquiring a time series containing data of the sensors with respect to a current run of the apparatus, wherein each sensor is configured to monitor a parameter of the apparatus or a parameter of an environment of the apparatus, respectively, wherein cumulative counts of errors occurring during a run of the apparatus are calculated for each type of an error and provided within the time series, wherein an error occurs when a parameter monitored by a sensor breaches a pre-defined threshold, wherein a linearly decreasing remaining useful life for each previous run of the apparatus indicating breakdowns of the apparatus by a value of zero is calculated and provided within the time series, - mapping the breakdowns of the apparatus as points in an error space, wherein each dimension of the error space refers to one type of an error, respectively, wherein the breakdown points are mapped at coordinates (42, 43) which represent cumulative error counts at the time of the breakdowns, - mapping a test point in the error space, wherein the test point represents cumulative error counts for the apparatus in operation, - identifying at least two nearest breakdown points with respect to the test point by calculating and comparing distances of the test point to all breakdown points mapped in error space, - calculating the remaining useful life of the apparatus which is a function of a quotient of a distance of the test point to an origin of the error space and a mean distance of the at least two nearest breakdown points to the origin.