The mathematical models for the economic evaluation of tidal power development involving a primary and secondary markets are presented in the context of utilities' generation expansion planning. The approach is to determine the economic benefits of tidal power by the difference in the least-cost expansion plans with and without tidal development. The least-cost expansion plans are derived by a series of snapshot year simulation and generation mix optimization. The impact of storage devices and transmission between market areas are properly studied. These models have been successfully applied to the study of tidal power in the Bay of Fundy.