Due to the low communication overhead and robustness to failures, distributed energy management is of paramount importance in smart grids, especially in microgrids, which feature distributed generation (DG). Distributed economic dispatch for a microgrid with renewable penetration and demand-side management operating in the grid-connected mode is considered in this paper. To address the challenge of intrinsically stochastic availability of renewable energy sources (RES), a novel power scheduling approach involving the actual renewable energy as well as the energy traded with the main grid is introduced, effecting the supply-demand balance. Its optimality amounts to minimizing the microgrid net cost, which includes conventional DG cost as well as worst-case transaction cost stemming from the uncertainty in RES. Leveraging the dual decomposition, the optimization problem formulated is solved in a distributed fashion. Numerical results are reported to corroborate the effectiveness of the novel approach.