This is based on a UCS 2012 report, "State of Charge", with some updates.
This is based on information from Alan Durning's Sightline Institute.
So I cannot complain in any great detail about the sourcing -- these are suspicious, petrochemical greenwashers.
The Stranger article compares a base model Tesla S to a Prius C. The Prius C comes out ahead if you charge in Bellevue using the utility but the Tesla wins in Seattle using the Seattle. And the Prius C only _barely_ comes out ahead on the Eastside. All PSE has to do is reduce its usage of coal power and voila. One of the least efficient of the BEVs wins. Don't lose track of the "C" on the Prius, either -- that does mean something! Good luck lining 3 car seats up in the back of a Prius C (go on -- do it and post the picture in a comment!).
Here's the data out of the NYT summary of the UCS update to the 2012 State of Charge report:
"That means an electric vehicle operating within the Midwest electric power grid, which blankets several states in whole or in part, is now as clean as a gasoline-engine car achieving 43 miles per gallon. In 2012, that number was said to be 39 m.p.g.
Some states that don’t depend heavily on coal for power generation fare much better. An electric vehicle in New York achieves the equivalent of 112 m.p.g., according to the scientist group’s data, while in California the number is 95 m.p.g. Others still lag behind. Colorado, which relies heavily on coal, is once again at the bottom of the list, with an E.V. achieving the same emissions as a 34 m.p.g. gasoline-engine car."
You should feel really pretty awesome driving your Prius or other hybrid, plug in or not, that is getting over 30 mpg. You should! Really! But don't let someone make you feel bad about switching to an electric car. Especially if you also put PVs on your roof.
And the link for the UCS report: http://www.ucsusa.org/assets/documents/clean_vehicles/electric-car-global-warming-emissions-report.pdf