AutoEcoRating™ is a freshened, up-to-date rendition of the green car rating systems that I created in the past. It follows the same lifecycle principles as earlier systems, but covers more vehicles and uses an open-ended scale that enables AutoEcoRating (“eRating”) comparisons across many model years. It also enables ratings of super-green vehicles that we hope we’ll see in the years a head.

By way of background, the other green car rating systems I developed are still being published and remain good guides to environmental friendliness. As is AutoEcoRating, all of these systems use an approach described in a peer-reviewed article, “A Method for Green Rating of Automobiles,” published in the Journal of Industrial Ecology.

The green rating system designed for use by Yahoo! Autos was developed several years ago when I was at the Environmental Defense Fund (EDF). I set it up as a simplified, “turnkey” system that Yahoo! programmers could implement on their own and they’ve been using it to rate new vehicles as they come onto the market. The Yahoo! Autos green ratings are given on a linear 0-100 scale.

The original lifecycle-based rating system I’d developed in 1996-97 for ACEEE’s Green Book is still in use at That system involves running a computer model every year and produces perfectly good ecoratings, or “green scores” as they’re termed by ACEEE (the American Council for an Energy-Efficient Economy). The Green Book’s scores also appear on a 0-100 scale, but one that “grades on a curve” and so is not the same as the Yahoo! Green Rating scale, even though relative comparisons are very similar for most vehicles.

The new system used here on AutoEcoRating updates both of these systems and uses an open-ended rather than a bounded scale (such as 0-100). That way it can accommodate a wide range of vehicles with high accuracy, allowing ready comparisons of both new and old vehicles according to the same eRating yardstick. Because there’s no upper bound, the AutoEcoRating scale will provide apples-to-apples ratings for very green vehicles, even experimental ones or small clean vehicles such as electric scooters. We’ve not yet tracked down and crunched the numbers for anything quite like that, but when we do, we’ll see some pretty high eRatings for sure.


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