With the increasing utilization of marine space and resources, ecosystem-based approaches to environmental assessments are requested. In this study the Ecological Risk Assessment (EcoRA) framework was used to outline risks from three ocean energy technologies; wave power, tidal current power, and ocean thermal energy conversion (OTEC). Our findings show that the potential risks from these new technologies include a multitude of ecosystem components and biological processes, which stretch over large spatiotemporal scales and motivate, the use of ecosystem-level assessment endpoints. In order to structure environmental assessments with such complex scope, assessment endpoints may preferably be associated with resilience in terms of maintaining ecosystem services. Moreover, cumulative effects from multiple stressors should be included. The systematic EcoRA methodology seems an appropriate tool for proactively assessing the risks from new technologies, such as ocean energy, in the complex and strained ocean environment.