There is a huge global demand for clean renewable energy sources to compensate for energy-related carbon dioxide (CO 2 ) emissions. The widespread development of multi-megawatt wind turbines with increased energy efficiency is playing an important role in meeting this demand for clean energy. Traceable efficiency measurements for wind turbines on test benches or in the field are thus very crucial. They are also of great interest for evaluating the usability of wind energy. However, no standardized methods are currently available for the traceable efficiency determination of wind turbines on test benches during the design phase. In this paper, a review of standards of efficiency measurements for rotating electrical machines on test benches is summarized. Furthermore, an innovative measurement concept for small-scale test benches with results that are similar to those of nacelle test benches for wind turbines is presented.