The Baseline Space Station Freedom architecture calls for separate and independent water electrolysis subsystems in ECLSS and in Propulsion. A study to assess the potential benefits and impacts of electrolyzer commonality evaluated fifteen sets of ECLSS and Propulsion architectural options with graduated levels of commonality, first by quantifying the electrical power, weight, volume, and heat rejection requirements; and then qualitatively according to safety and redundancy, reliability and maintainability, integration and verification, and assembly. There were no compelling quantitative or qualitative advantages of the options incorporating commonality which would drive a decision to alter the Baseline. The options were also compared with respect to estimated program costs. The maximum projected savings were less than five per cent, likely within the uncertainty of the estimation process. The overall conclusion reached was that the Baseline, of independent unit design and subsystem architectures, should be retained.