Climate change and dwindling of fossil resources necessitate a shift away from fossil fuels and toward renewable energy production. Wind, solar, and hydropower are examples of this kind of required renewable technologies. These types of energy production is subject to significant fluctuations due to the influence of the prevailing weather conditions. Since energy consumption does not generally match these fluctuations, additional flexibility options in the energy supply system are required. The reversible high-temperature solid oxide cell (rSOC) offers a promising new technology for this purpose. rSOC systems can be used as energy storage systems by combining fuel cell and electrolysis operations in a single cell. They also enable the coupling of energy sectors like heat, gas, and electricity. An rSOC system's electrical grid integration, which permits bidirectional power flow, calls for extensive power electronics. As part of the FIRST research project, the operating characteristics of these power electronics have been thoroughly investigated and characterized in this work. An approach known as power-hardware-in-the-loop (PHIL) was chosen. It enables laboratory tests under actual working load scenarios and features a comprehensive SCADA system for data logging, to thoroughly describe the power electronics. Additionally, the PHIL method enables selective exposure of predefined rSOC system operating points. For in-depth data analysis, the electrical properties of the power electronics were captured in high resolution. To characterize the power electronics, the power and efficiencies were calculated based on the measured data, the time characteristics of voltage and current were displayed, the ripple current components of direct currents were quantified, and the harmonics that occurred were determined using a harmonic analysis. The generated results also allowed the developed experimental setup to be validated. Causes of potential inaccuracies were identified, and the results were critically examined. Finally, the results of the characterization were discussed, and recommendations for improvement were made.