To assure the environmental benefits of hydrogen as an energy carrier, renewable sources of electricity will be used to a large extent to split water into its two constituent parts.  NREL is working with the electrolyzer industry and electric utilities to improve the integration and performance of renewable hydrogen production via electrolysis. There exists opportunities to improve the matching of renewable sources and the hydrogen producing electrolyzers by designing systems to accommodate the natural variability of these energy sources.  A collaborative demonstration project between Xcel Energy and NREL is researching these opportunities to increase the energy capture of wind- and solar-electric systems to hydrogen production, compression, storage and grid-connected electricity generation.  NREL is working to improve the power electronic controllers between these systems to enable an increase in electrolyzer system efficiency.  Improved energy capture from successive generations of 10 kW power controllers that condition variable magnitude/frequency alternating current (AC) to the direct current (DC) requirements of the electrolyzer stack will be shared.  In addition, initial results of a DC/DC power controller being designed and built to interface a 100 kW variable-speed wind turbine to a 30 kW electrolyzer stack will be presented.  Lessons learned from the design, build and testing of the renewable energy to hydrogen system will also provided.