System-level costs per kW of rated power. These include, among others, control systems, thermal management, housing, hydrogen supply except for storage, air intake, including compressor and humidifier and assembly. Black circle markers represent the original harmonized data. Solid lines represent the regression results (loglog, WLS, mean values), with the shaded areas (that is, error bars) in the zoom-level plot (period 20202050) as 95% confidence intervals (mean ± 2 s.e.m.). The source category is colour coded: near market (blue: analysts, consultancies, industry announcements), scientific (green: peer-reviewed papers) and others (purple: non-peer-reviewed academic publications). Total results (that is, cross-category) in black. The total sample size covers N = 424 data points from 83 unique studies. Cross-category R 2 is 0.33. The figure legend states the number of data points ( N ) and the R 2 values per source category. Additional information is available in Supplementary Tables 1 and 4 .
