Solar energy reaches your car as visible light, ultraviolet and infrared, and it is the infrared part, invisible but a significant share of the heat you feel, that makes a parked Tesla uncomfortable. Kepler's nano-ceramic films are engineered around that infrared energy, which is why they can work on cabin heat without relying on a very dark appearance. Visible light transmission tells you how much light passes through a given shade; it is a separate measure from solar heat performance, so compare the exact film and shade with your installer, who can also advise on the glazing fitted to your car.