Total heat rejection seems to be in the range of 34 to 60 percent depending on selected film, which is pretty good. I'd consider it for my van if it was newer and I was going to keep it a while.
Crystalline Automotive Films - Clear automotive window film for cars, trucks - Crystalline - 3M US
From the linked MotorTrend article:
"For that, 3M’s technicians were on hand to answer questions regarding the Crystalline series’ performance. According to 3M, the company’s clear films will allow anywhere from 40 percent to 90 percent of visible light into a car, depending on which grade is chosen. Also dependent upon which grade is chosen is the amount of solar energy rejected, which ranges from 34 percent to 60 percent. To put that into perspective, the darkest conventional tint 3M offers only rejects 45 percent of solar energy while allowing only 6 percent of visible light in. Although the amount of light and heat let in varies, 3M claims that all films in the Crystalline line reject 99.9 percent of UV radiation and 90 to 97 percent of infrared radiation. Because these films significantly reduce exposure to UV rays, they are recommended by the Skin Cancer Foundation as an effective defense against ultra violet radiation — which it identifies as a leading cause of skin cancer."