After overcoming major start-up problems, 1 guarantee test runs were successfully completed in February 1993 on the phosphoric acid fuel cell plant (79 kW(dc), 4 kW(th)) installed at the SWB solar hydrogen facility in Neunburg vorm Wald, Germany. The fuel cell plant comprises a fuel cell, a steam reformer with CO shift converter, and a pressure-swing adsorption unit. This article describes the fuel cell plant in detail. The most significant results of the guarantee test runs and specific knowledge derived from operation up to August 1994 are reported. The fuel cell plant described in this article was set up for testing within a solar hydrogen demonstration facility. In designing the plant, efforts were undertaken to incorporate an extensive variety of operating capabilities. Accordingly, we are not concerned here with a commercial containerised production unit but with an experimental plant installed for test purposes.