Longatto, Here is a video comparison we did a while back. 1) The Porsche GT3 had Huper 50% on the front windows. (We eventually replaced it with Spectra Photosync.) vs. 2) The Nissan Leaf have Photosync 55% in comparison. (5% lighter, but better performance) Notice the performance difference from the BTU meter. The BTU meter is not the end all for measuring heat, it does give a general sense for the performance of a window film.