The industry traditionally talks about PEM Electrolyser efficiency at Beginning of Life, however it is increasingly important to consider the lifetime cost of green hydrogen generation, where minimising the long-term cell degradation rate has a big impact on the operational cost of an electrolyser over 10 years, or 80,000 hours.  An understanding of these degradation mechanisms and the identification of technology to minimise degradation rate has a significant impact on the long-term cost of green hydrogen generation. In this presentation Dr. Srijita Nundy will discuss further the importance of degradation, the mechanisms by which this can occur, as well as presenting the various ways to minimise the degradation rate to improve efficiency and lifetime operational cost.