Quantifying the return on investment for a rooftop solar installation isn’t a simple task. But a relatively new mapping tool from MIT’s Sustainable Design Lab aims to facilitate the process. Mapdwell, which launched in May 2013, provides data on the costs and benefits associated with installing a photovoltaic system on a given building. Initially covering the university’s hometown of Cambridge, Mass., the company announced on Nov. 11 that it has expanded the online service to include Washington, D.C., through a partnership with the District’s Department of the Environment.

By including the nation’s capitol, the tool takes stock of the solar potential of nearly 160,000 buildings’ roof topography—space that could be used to generate more than 2.5 gigawatts of electric solar power annually. The platform also identifies more than 800 existing installations in the District that together produce an installed annual capacity of approximately 4,228 kW.

Designed to inform stakeholders in urban communities about the solar potential of their structures, Mapdwell uses high-resolution lighting detection and ranging data to create interactive 3D models based on solar irradiation per surface unit and accounting for variables such as building and roof shape, existing infrastructure, and tree shading. The high-level analysis tags structures’ solar potential as one of five categories—poor, average, good, optimal, or information not available. For each building, the toll provides metrics for a selection of variables based on the size of the system, including cost to owner, payback period, carbon offset, electricity output, carbon offset, local utility rate, and potential energy cost savings.

While Mapdwell notes that the tool isn’t a substitute for an on-site evaluation, the company says it turned out a 3 percent to 5 percent margin of error during validation testing.

Check out the tool here.