From the article: "And yet, in terms of greenhouse-gas emissions, grid-charged cars are still cleaner than their gasoline-powered counterparts, and that's particularly true in California, where we rely largely on natural gas to make electricity."

I would like to see some documentation or discussion regarding the above claim, especially with respect to coal, the most carbon intensive fuel there is for producing electricity. And I would also like to see the full energy accounting with respect to miles per equivalent units of energy. Is there a high energy cost to producing batteries, for example. With regard to burning fuel derived from cellulosic material, the Gaffneys of the world make this sound like there's a free lunch.

You know. We just can't let go of our automobile dominated society. I would like to see a day where cars are largely unnecessary. I'll drive my Prius in the mean time. But I can dream, can't I?

I don't seem to understand why anyone would want to plug-in a Prius. The battery cannot store very much energy anyway. Even if it were at its lower limit when you pulled into the garage at night and you managed to charge it to its upper limit (as defined by Toyota) how much gasonline do you think that would really save? I think you would find it very very minimal.

Now if you managed to put a larger battery in the car you might gain something, but again I don't think much. You would give up space plus you would add weight which would chew into your gas mileage. I think Toyota did a good job with the car as it is.

Another concern is the cost of electricity. It is very expensive on Long Island, so I have to wonder if the money you save on gas would just go to the electric bill. Now if we start installing wind turbines on a large scale, that might help. Wind turbines are a no-brainer. Build them and you recover the construction costs in a year or two. After that it is free energy.

Hi Kirbinster,

It looks like the article has now become registered users only - sorry! The plug-in Prius in question is this one, and yes the original battery has been removed and replaced with a much larger capacity battery - adding about 60 kilos to the car. The battery is charged from a wall outlet.

It can travel about 45 miles in "assist" mode, where the energy in the battery from the overnight charge "helps" the engine, so much less gasoline is used. The reporter in the above article averaged 144 mpg and used 7 kilowatt-hours of electricity. That was on a mix of roads and conditions.

Hi Jared,

You asked about costs per mile, assuming an electricity price of 10 cents per kilowatt-hour (less if charging off-peak), the above figures work out at 1.5 cents per mile electricity costs and 1.6 cents per mile gasoline costs - so just over 3 cents per mile fuel costs. But the more often you fill up with electric instead of gas, the cheaper it gets.

Hi tstreet,

The whole coal thing is a big dicussion! But to condense things a bit, coal burning power plants release about 800 grammes of CO2 for every kilowatt-hour produced. A Prius-PHEV can go about 5 miles per kilowatt-hour, which equates to about 160 g CO2 per mile (or about half this if the electricity is made from natural gas). A Prius managing 50 mpg releases about 185 g CO2 per mile.

So the short answer is we need to move on from coal as soon as possible!

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Thanks Clett, that is sort of what I figured, and it could make sense in some areas, but probably not the NY-NJ area where electricity can be very expensive. Your electric figures are low for the summer-time where I live. Currently electricity is about 18 cents a KWH in the day and about 14 cents at night. Part of the reason I installed solar panels on my roof.