High temperature fuel cells can be designed and operated to poly-generate electricity heat and useful chemicals (e g hydrogen) in a variety of configurations The highly integrated and synergistic nature of poly-generating high temperature fuel cells however precludes a simple definition of efficiency for analysis and comparison of performance to traditional methods There is a need to develop and define a methodology to calculate each of the co-product efficiencies that is useful for comparative analyses Methodologies for calculating poly-generation efficiencies an defined and discussed The methodologies are applied to analysis of a Hydrogen Energy Station (H2ES) showing that high conversion efficiency can be achieved for poly-generation of electricity and hydrogen (c) 2010 Elsevier B V All rights reserved