At http://www.hybridcars.com/­blogs/­power/­why-no-cars, I've fixed a division error and added info on the CO2. Here's revised text

A green-letter Thursday: 20 miles of high-speed driving, then 10 short-trip errands that used to kill my Prius MPG -- including my first visit with the converted car to my Prius dealer, where a crowd of salespeople gathered in wonder and admiration. My display when my batteries were depleted after driving 42.9 miles showed 137.8 MPG + electricity used at 146 watt-hours/mile. Translating with gas @$3, stock Prius @48MPG, average car @25MPG, national average electricity @8.5 cents/kiloWatt-hour (I'll soon be able to add a factor for energy losses charging the battery):

Standard car: 1.716 gallons = $5.15
Stock Prius: 0.893 gallons = $2.68
PHEV Prius: .311 gallons=$0.93+6.26kWh=$0.53. Total=$1.46
This illustrates why we talk about electricity at $1/gallon equivalent.
Any questions? Here's mine: how much better could it be in a production PHEV?

Of course, it's not just the economics 1. Oil dependency: I used 18% as much gasoline as a normal car and 34% as much as a Prius. 2. Global warming: no derived calculations, but here's Joe Romm's general summary of well-to-wheel CO2 annual emissions for 12,00 miles: Standard car: 12,000 pounds Stock Prius: 6,000 pounds PHEV Prius: 2,000 pounds in CA (That's on the California grid; it's 3,900 even on the national grid, which will get cleaner)