From http://labs.autodesk.com/utilities/ecotect/

Use the Solar Radiation Technology Preview to analyze the effects of solar radiation on various surfaces of your conceptual building model. Using the Solar Radiation Technology Preview during the conceptual design stage of your project can help you make fundamental design decisions about building shape, orientation, and surfaces early on, when changes are least expensive. The technology preview uses the geometry of conceptual massing elements from Revit and calculates the amount of solar radiation hitting the surfaces of the massing shapes, based on location and weather data. It is possible to display the distribution and availability of solar radiation over an entire building or even a city block. This can be particularly useful when considering shading requirements or assessing the best areas to place photovoltaics for maximum collection.

The output of the technology preview can be saved as images in the Revit project that contains the massing elements. After these images are added to the project, you can place them on sheets and print them. You can also export the images from Revit for use in presentations or for editing in external software applications.