Renewable energy systems are the final step to attaining zero energy goals. Once all possible measures to reduce energy demand are deployed, renewable energy systems must step in to balance residual energy demand. Performance of renewable energy systems determines the success of the net-zero buildings.Renewable energy systems can be integrated during the early design process as a part of the structure, or could be added as retrofits. While solar energy is ubiquitous, but other renewable energy sources are highly location specific.