One thing I did notice for sure is with heat, lights, etc., on, the Wh/mi reading does click up of --- but very, very slowly. It seems to me just from looking at how it moves though, that driving the car actually uses up much, much more energy than what the accessories are using. Obviously, the faster you drive, the less the impact of the accessories in exact proportion to your speed. It just feels from watching the meters like the accessories are not eating up that much power. That's logical when you think about the power that is needed to propell a 2,500 lb. automobilie.