Investments in renewable energy plants normally only take standard economic key figures into account, such as installed rated power, the market price of energy and the interest rate. The authors propose that the degree of utilisation, i.e. the ratio of yearly produced energy in the installation to the installed power, must be included due to its significant impact on the present value of the investment. A site with a limited average wave height could be of economic interest if the utility factor for the installation is high, since the investment cost (associated with the power installed) can be better adjusted to conditions at the particular site. In the case of wave power from the Baltic Sea with its limited variation in wave height (and limited average wave height), this indicates that the economic potential is best for smaller units.