Zwaschka, GregorGregorZwaschkaThiel, LauraLauraThielLeskau, RomanRomanLeskau2025-06-022025-06-022025https://publica.fraunhofer.de/handle/publica/48811510.1016/j.ijhydene.2025.05.1462-s2.0-105004926689Increasing the temperature of PEM electrolyzers improves their efficiency but reduces their lifetime. This suggests the existence of an ideal temperature - characterized by a minimum hydrogen price - at which the electrolyzer is sufficiently efficient and long lived. Here, we evaluate the ideal temperature of a PEM electrolyzer as a function of material (membrane thickness, exchange current density), operational (current density, voltage degradation) and economic parameters (CAPEX, OPEX and electricity price). Increases in efficiency with temperature are calculated from a cell model. The lifetime decrease is taken from literature data and is supported by a model of PEM degradation. The ideal operating temperature decreases from 80 °C at 0.15 €/kWh (and higher) to 40 °C at 0.01 €/kWh. The relative influence of material, operational and economic parameters on the levelized cost of hydrogen is quantified, allowing for clear recommendations on a path to cost competitive hydrogen.enfalseCost optimizationDegradationEfficiencyHydrogenLifetimePEM electrolysisjournal article