In the present investigation, the thermodynamic analysis of a solid oxide fuel cell based on protonic electrolyte (SOFC(H(+))) and fed with hydrogen is performed. The influence of such parameters as hydrogen purity, air humidity, hydrogen and oxygen utilization as well as working temperature on them fuel cell efficiency is established. The results obtained show that the hydrogen fed SOFC(H(+)) has an essential advantage as compared to the hydrogen fed SOFC based on an oxygen ion electrolyte (SOFC (O(2-))) regarding the efficiency of chemical energy to electrical power transformation. It was established that the maximum SOFC(H(+)) efficiency in the range between 1000 and 1300 K exceeds 80%, which is significantly higher than that of the SOFC(O(2-)). It was also estimated that the SOFC(H(+)) efficiency at 1000 K is about 70% when it runs at 60% of its maximum power, whereas the practically reachable SOFC (O(2-)) efficiency under the above-mentioned conditions is less than 55%.