Methods, systems, and apparatus, including medium-encoded computer program products, for determining optimal grid interconnections. A power grid model that includes a topological representation of a power grid and electrical specifications of grid components can be accessed. First interconnection data representing a first proposed interconnection to the power grid can be obtained. At least one other proposed interconnection to the power grid can be selected. A modified power grid model can be generated at least by incorporating the first proposed interconnection and the at least one other proposed interconnection into the power grid model. A simulation of the power grid can be executed using the modified power grid model to obtain simulated power grid data. A combined impact of the first proposed interconnection and the at least one other proposed interconnection on the power grid can be determined from the simulated power grid data.