The determination of the required reserve levels due to the incremental trend of injecting wind energy into the power grid with a high level of wind energy penetration is complicated because of the variability of wind energy. This study proposes a method, based on the logarithmic barrier interior point method for optimal power flow and Monte Carlo analysis, to evaluate the required reserve levels for a grid with variable generation. A Gaussian distribution was used to model the dynamic load demand, while a unique linearized least-square approximation was used to model the wind turbines. In order to demonstrate the capability of the proposed algorithm, the methodology was applied to a modified IEEE 30-bus system with two wind-farms. The simulation results showed that the determined reserve requirement was considerably reduced compared with that obtained with classical approaches. The proposed method also satisfies all the considered constraints and maintains system reliability. (C) 2017 Elsevier Ltd. All rights reserved.