This paper’s main contribution is a theoretical result that can be used to evaluate the maximum powergenerating potential of any kite-power system. An upper bound is derived for the power a wing can generate in a given wind speed. It is proven that the angle of the restraining forces on the system modulates this upper bound. In order to derive practically useful results, this is linked to the strength-to-weight ratio of the different system components through an efficiency factor. The result is a simple analytic expression that can be used to calculate the maximum power-producing potential for any system of lifting surfaces, dynamic or static, supported by a tether. As an example, the analysis is applied to two systems currently under development, namely, pumping-cycle generators and jet-stream wind power.