This paper looks at the development of a Techno-Economic Assessment (TEA) for tidal energy converters. The TEA has been established to help developers by providing a high-level assessment of their tidal energy conversion device which gives an estimate of the affordability offered by the technology for a given resource. The affordability of the device is ultimately what will determine its commercial success and therefore being a decisive metric in supporting the development of a technology. To estimate the affordability of the device the TEA considers the fundamentals that impact on the costs and revenue thus evaluating the core design. Using different inputs to the TEA that represent different design approaches allows the developer to make design choices based on the outputs of the tool. This allows multiple design options to be analysed at an early stage of the design process, to establish the most promising configuration that could result in a commercial solution. The TEA aims to help developers at low TRLs as this is where the largest benefit can be realised. However, the assessment can still be used at higher TRLs to evaluate different approaches and to confirm progress. By carrying out this TEA at early TRLs it supports developers throughout the development of their technology, helping to find the optimal solution at the earliest development stage. This approach identifies areas of high risk early in the development program, a stage where costs and the impacts of change are lower.