Proton OnSite designs, develops, and manufactures proton exchange membrane (PEM) electrochemical systems to make hydrogen from water for customers in the United States and internationally. Its products include onsite hydrogen generation systems for laboratories, silicon semiconductor and metal organic chemical vapor deposition processes, materials processing, and meteorological applications; and PEM electrolysis systems for centralized fueling and neighborhood fueling. The company also offers regenerative fuel cell systems for traditional lead acid batteries and diesel generator sets. It serves military, aerospace, fueling, and renewable energy industries. The company was formerly known as Proton Energy Systems, Inc. and changed its name to Proton OnSite in April 2011.

Proton OnSite was formally accepted as a member of EHA as of 21 June 2012