Harness of wave and tidal energies can play an important role in the future energy portfolios to ensure the energy security and to reach the low-carbon energy development plans. However, despite the existence of adequate resources of these energies through the world, they have not been well exploited yet. This study has focused on the assessment of the economic criteria and their relative importance for the development of the wave and tidal energy technologies based on the experts' judgment. To this end, the expert elicitation process was performed using the Delphi methodology. 5 main criteria and 29 sub-criteria were initially identified through a comprehensive literature review. During two rounds of Delphi questionnaires, the degree of importance and the degree of consensus values were identified for each individual parameter. According to the results achieved, selling the energy produced and tax incentives were rated as the most important factors with the highest degrees of consensus. While quotas and tenders were not identified by the experts participated in the survey with high importance on the development of wave and tidal energies although with low degrees of consensus.