The Shading Coefficient (SC) of a film is the number that expresses the heat reduction of that film. In the window film industry, it is defined as the ratio of BTU's (heat) coming through the filmed glass as compared to the BTU's coming through the glass without film. The lower the number, the better the heat reduction.
This is the number that architects & engineers use in heat load calculations, and it is how we represent the heat reduction of our films.
Total Solar Energy Rejected is a quantity used by many window film dealers to express the heat reduction of their film. It is a measure of the energy reduced over the entire solar spectrum, not just the heat portion. It is inflated and inaccurate and we never use it. The true measure of heat reduction is the Shading Coefficient, as explained above.