Tidal power is a predictable renewable energy source. However, tidal device development faces two main obstacles: high cost and reliability during its life expectancy. The blades make up a significant part of total tidal turbine cost. Hence, the capital cost reduction and the structural reliability of blades are the key factors in a tidal turbine development. This study examines the possibility of replacing Glass Fibre Reinforced Composites (GFRP) with Carbon Fibre Reinforced Composites (CFRP) in the design of tidal turbine blade structures in order to reduce the weight and cost of the blades. The benchmark for this study is the development of 1MW blades for a major floating tidal turbine developer.