Cost-effective expansion of the wind energy industry benefits from robust estimates of wind resource and operating conditions. Extreme design loads contribute to wind turbine selection and cost, and are determined in part by the fifty year return period sustained wind speed (U50). Here we derive a global, homogenized and geospatially explicit digital atlas of U50 and associated confidence intervals based on ERA5 reanalysis output at wind turbine hub heights. U50 estimates derived using ERA5 output and four different methods are shown to lie within an average of 9–13% of those from point measurements. The reference wind speed (Uref) derived using five times the mean wind speed as specified in the wind turbine design standards is generally a conservative estimate of U50. Particularly after application of additional safety factors, this may result in over-engineering of wind turbines and excess capital expenditures.