Fuel cell based backup power systems are finding application in telecommunication applications. Due to the criticality of the application, as well as the effort of keeping operating costs low, appropriate maintenance strategies are of high importance. This paper investigates key performance indicators, derived from numerous fuel cell based backup systems, installed in the field. The methods of principal component analysis and local outlier factor are applied to the KPIs, in order to identify systems that are performing differently from the majority of the systems. These underperforming systems can then be examined closer to identify potential problems.