To date the estimation of long-term wave energy production at a given deployment site has commonlybeen limited to a consideration of the significant wave height H s and mean energy period T e . This paperaddresses the sensitivity of power production from wave energy converters to the wave groupiness andspectral bandwidth of sea states. Linear and non-linear systems are implemented to simulate theresponse of converters equipped with realistic power take-off devices in real sea states. It is shown inparticular that, when the converters are not much sensitive to wave directionality, the bandwidthcharacteristic is appropriate to complete the set of overall wave parameters describing the sea state forthe purpose of estimating wave energy production.