In this contribution, we propose an experimentally-validated systemlevel model of a magnetoelectric transducer and a general methodology for future characterization of similar transducers. This methodology provides insights into the main origin of power losses. An analogy with piezoelectric generators leads to a system-level figure of merit which is strongly impacted by the nonlinear behavior of the transducer. Considering the complexity of the observed nonlinear behavior, we opt for a grey-box model of the dependencies between the transducer characteristics and the operating point. Applying our methodology to an optimized sample shows that nonlinear mechanical losses are the main origin of power dissipation. The maximum transferable power is proven to be up to 61% lower than the power one would expect from a linear characterization.