Likewise for the transport sector, grid problems are reflected in mean time between failures (MTBF). In order to calculate the blackout probability for a huge number of different situations, probabilities have been attached to input factors in two ways, either deterministic or probabilistic. In a first step, a low, base or high value can be chosen for each input parameter. By using a special macro, one variable is changed at a time in a deterministic sense. This results in a Tornado diagram that ranks the results of the preceding singlefactor sensitivity analysis. In a next step, using the Excel-based Palisades @RISK programme, a Monte Carlo value is drawn ffom a triangular distribution with low, base and high values having a 10%, 50% and 90% probability.