A naval submarine sails in different operational modes: surfaced, at periscope depth or submerged. It needs an appropriate power plant to do so. The impact of the selected power plant on the overall submarine design is significant. Selecting the right components of the power plant in an early stage is therefore key to a successful design. Current early-stage design methods are based on known design solutions like diesel-electric or fuel-cell driven power plants and have difficulty coping with novel solutions like a combination of diesel-electric and fuel cells or permanent magnet propulsion motors. An earlier developed mean value first principle power plant model is extended in this research with a PEM Fuel Cell model as Air Independent Power (AIP) system and a Permanent Magnet Synchronous Machine model as propulsion motor. The overall power plant model covers energy generation, storage and distribution to the main power demands “propulsion” and “auxiliary”. The model enables optimization of a submarine power plant to balance the required space, mass and operational performances based on a pre-set operational profile. A total of eight configurations (mix of Lead acid or Li-Ion battery, Fuel Cell AIP, compound or permanent magnet motor) were assessed against ten operational profiles. The result is insight into optimized design concepts considering volume, mass and efficiency (ultimately operational cost) given operational needs that extend beyond current submarine capabilities.@en