In this paper a Concept Exploration Tool (CET) for naval ship power plants is presented. The ideas behind the CET are introduced as well as the inner workings of the tool. Objective functions for different relevant design criteria (energy efficiency, emissions, signatures, etc.) are shortly discussed, after which the results for a Frigate case study will be shown. Interesting solutions that are outside the well-known zone of conventional configurations, that may lead to new insights and innovative designs, are amongst the results of the CET; demonstrating the advantages of Design Space Exploration. The main development of this CET compared to earlier versions is however in the computational effectiveness of the tool, which is amongst others made possible by so-called Intermediate Design Algorithms (IDeAs). The major improvement in computational time provides additional room for further development of the objective functions used.