NYSE:ENR 14 August 2025 - 18 November 2025

Hydrogen electrolyzers are at the heart of the green hydrogen revolution. In this comprehensive comparison, we explore the three leading water electrolysis technologies – Proton Exchange Membrane, Alkaline, and Solid Oxide electrolyzers – highlighting how each works, their efficiency, costs, durability, and latest developments as of 2024–2025. We’ll also look at which technologies suit intermittent renewables, who the market leaders are, new innovations on the horizon, environmental considerations, and what experts are saying about the future of these electrolyzers. Alkaline Electrolyzers: Alkaline systems are the oldest and most established electrolyzer technology. They use a liquid electrolyte and nickel-based electrodes. When a current is applied, water at the cathode splits to produce hydrogen gas and hydroxide ions. The OH⁻ ions migrate through the electrolyte to the anode, where they combine to form oxygen gas and water energy.gov energy.gov. The overall reaction is simply water being split into H₂ and O₂. Because the electrolyte is liquid, alkaline cells typically operate at moderate temperatures energy.gov stargatehydrogen.com. This mature design has been used for decades and is known for its robustness and simplicity. Hydrogen output from alkaline electrolyzers is high-purity but can contain small moisture or KOH traces, so downstream purification may be needed