The ‘Tier IV Final’ regulations developed for Diesel generators were proposed over 15 years ago and aftertreatment technology advancements have increased dramatically, providing ultraclean levels of performance. In the overwhelming majority of the country, a Tier V level diesel generator provides power to the facility that is actually cleaner than the grid. The parameter ‘GVU’ proves out the disparity and documents the counterintuitive green balance between onsite generation versus Utility.