Conventional concentrator photovoltaics (CPV) employing two-axis tracking are generally only economically competitive with cheaper, less efficient alternatives in locations with large amounts of direct sunlight. Adding a diffuse light collector to a CPV panel in the form of a silicon back panel can potentially improve the light collection under cloudy conditions and expand the range of climates in which CPV is useful. However, to understand the performance advantages available with diffuse collection, a realistic forecasting tool to predict performance in different locations is required. We introduce a model to evaluate the annual energy yield of a hybrid CPV and Si module and compare the results with several conventional stand-alone Si and CPV modules. The advantages of including a bifacial Si panel as the diffuse collector will also be investigated.