Wind power in the NE (Northeast) region of Brazil is currently undergoing rapid development and installed capacity is expected to exceed 16,000 MW by 2020. This study examines the feasibility of integrating large scale wind power into an electricity grid (the Brazilian NE subsystem) which has a high proportion of existing hydroelectricity. By extrapolating existing wind power generation data, the maximum achievable wind power penetration (without exports to other Brazilian regions) and corresponding surplus energy is determined for the NE subsystem. The viable maximum penetration of wind energy generation in the NE subsystem was estimated to be 65% of the average annual electricity demand assuming that existing hydroelectric and gas generators have 100% scheduling flexibility. These results are compared to the actual gross penetration of wind power forecast to reach 55% in the NE subsystem by 2020. The overall LCOE (levelised cost of electricity) is calculated for various scenarios where wind power replaces all fossil fuel generators in NE subsystem. It was concluded that by 2020, wind power could feasibly reduce the overall LCOE by approximately 46-52% and reduce CO2eq emissions by 34 million tonnes per year compared to a power system with no new renewable generation. (c) 2015 Elsevier Ltd. All rights reserved.