Once the film has cured, look first at the finish: the edges should be neat, the film clean and free of debris, and the view through the glass clear and undistorted. For a rough sense of solar performance, park in direct sun, lower a tinted window partway and hold your hand behind the tinted and untinted sections in turn. Installers use infrared meters for a proper comparison, and published technical data for your exact film and shade is the reliable reference.
We also publish a guide to California window tint laws. View our guide on tint laws