This Code provides test procedures, methods and definitions for the performance characterization of fuel cell power systems. Fuel cell power systems include all components required in the conversion of input fuel and oxidizer into output electrical and thermal energy. Performance characterization of fuel systems includes evaluating system energy inputs and electrical and thermal outputs to determine fuel-to-electrical energy conversion efficiency and where applicable the overall thermal effectiveness. These efficiencies will be determined to an absolute uncertainty of less than ± 2% at a 95% confidence level. (For example, for a calculated efficiency of 40%, the true value lies between 38% and 42%.)