Abstract A high share of Brazilian power generation comes from hydropower sources and a further expansion of power generation is necessary due to high growth rates in electricity demand. As an alternative to the expansion of hydropower which shows high seasonal and annual variability with risks of load shedding due to droughts, windpower production may be increased. We assess the variability of potential windpower plants in the four most important windpower producing states Ceara (CE), Rio Grande do Norte (RN), Bahia (BA) and Rio Grande do Sul (RS) in comparison to adding new hydropower capacities in the North region. We assess seasonality and long-term deviations from seasonal production patterns. For that purpose, time series of windpower production from wind speeds derived from measurements and two global climate reanalysis models (NCAR and ECMWF) are generated and validated. Our results show that seasonal variability of windpower generation in the North-Eastern states is anticyclical to hydrological seasonality in the South-East, North-East, and North region of Brazil. Deviations of simulated windpower production from the monthly means are less correlated with current hydropower production than deviations of potential new hydropower projects. Adding windpower instead of hydropower to the system decreases significantly the risk of long periods of very low resource availability. The states Bahia and Rio Grande do Sul perform best with respect to that measure. Our validation procedure shows that ECMWF data may be the best source of long-term wind time series as it better reproduces ground measurements than NCAR.