Abstract. If the good performance of fusion as technology with no CO2 emission during normal operation and rather low external costs, reflecting the advantageous environmental and safety characteristics, are considered in future energy regulations, fusion can win considerable market shares in future electricity markets. The economic performance was elaborated for Western Europe for the time period till 2100. The software tool MARKAL widely used in energy research was used to simulate and optimise the development of the Western European energy system. Two different scenarios were considered, the main difference was the interest rate for investments. Stringent CO2-emission strategies lead to considerable market shares for fusion. As a comprehensive indicator of the environmental and safety performance of fusion plants the external costs following the ExternE method was used. External costs of fusion are rather low, much below the cost of electricity, and are in the same range as photovoltaics and wind energy.