Analysis of the development distances provides on the overall picture of (required) technological progress. To derive actionable insight, especially for informing research and development efforts, it is important to understand how much the underlying technological properties have to advance to achieve cost-competitive hydrogen production. To this end we can analyze the specific parameter values of models which reach the target cost range. In the following, the corresponding data will be visualized using colored scatter plots: each model with an LCOH2 in the target cost range is shown as a colored dot, with its (x, y) position and color determined by its parameter values (the fourth parameter which has been varied in the Monte Carlo simulation is not shown). For reference, the base case is also shown as a labelled and colored dot. From this visualization we can see which combinations of parameter values give rise to models with cost-competitive hydrogen production. Figure shows the colored scatter plot for PEC. Only a very small region of the parameter space gives rise to models in the target cost range, with this region being at the maximum distance from the base case. STH efficiency has to exceed 26%, cell cost has to be below 1500 $/m 2 (PEC Cell) and cell lifetime has to exceed 2 years. The central challenge for PEC is that the PEC cells are the most expensive component of the plant for most models (see cost breakdown in SI Figure .2-2), but also have a short lifetime (especially compared to solar cells and electrolyzers). This is because various components of the cell are exposed to a reactive chemical environment. Since PEC cells are by definition highly integrated devices, most components have to be replaced together at the end of their lifetime, leading to high replacement costs (see SI Figure .2-1) and thus a high LCOH2. Based on our results, only a combination of high efficiency (small area of cells needed for a given H2 production), low cost and long lifetime can overcome these challenges to reach the target cost range.