What is a residual mix?

The residual mix is nothing more than a adjusted grid emission factor. The difference between a grid emission factor and the residual mix is that the residual mix incorporates the allocation, procurement or use of renewable energy by those that have purchased electricity attribute tracking certificates like the guarantees of origin (GOs), renewable energy certificates (RECs) or international renewable energy certificates (I-RECs). When calculating a residual mix the methodology usually excludes cancellation or redemption information from the purchased electricity attributes and factors in actual physical electricity imports and exports. In this way the problem with double claiming of renewable attributes can be reduced.