Solid Oxide Electrolysis uses a ceramic electrolyte at temperatures up to nine hundred degrees Celsius, achieving theoretical efficiency of eighty-five percent. High-Temperature Steam Electrolysis goes further, using steam at up to one thousand degrees Celsius with theoretical efficiency of eighty percent. Both technologies produce high-purity hydrogen without expensive platinum catalysts and can use industrial waste heat to cut energy costs. Companies including Sunfire, Bloom Energy, Siemens Energy, Ceres Power, and FuelCell Energy are actively commercializing both technologies for the global green hydrogen market.