The supply of Nafion and Aquivion proton exchange membranes is currently severely constrained, prompting a search for alternatives. In this work, a new commercial proton exchange membrane (PFSA D170-U) was evaluated and compared with two other membranes: Nafion™ N117 and Aquivion® E98-15S. The performance, stability over 100 h, and H2 crossover characteristics of these three membranes were investigated in a flow cell electrolyser by testing each membrane type in triplicate using a fresh sample of membrane for each experimental run. At 60 °C, the three membranes showed an average performance of 1 A cm–2 at 2.0 V and an average degradation rate of 1.2 mV h–1 after stability tests for 100 h at a fixed current density of 1.0 A cm–2. The three membranes showed similar metrics, suggesting that PFSA D170-U is a promising proton exchange membrane alternative to Nafion and Aquivion membranes for research purposes. Additionally, the physical, morphological, structural, thermal and mechanical properties of the PFSA D170-U membrane were examined.