by John Gartner

Now that Toyota’s Prius Plug-in Hybrid has been officially announced, we can begin the comparisons with the other plug-in electric vehicle with an extended driving range, the Chevrolet Volt. The underlying question is which is more important to consumers: electric driving range, or total vehicle fuel efficiency?

The folks at Edmunds.com’s AutoObserver pointed out that the Prius PHEV will earn the right to drive in the HOV lane in California (because of the low total emissions), while Volt owners won’t have that luxury. Conversely, Volt buyers get the full federal tax credit ($7,500) because of the larger battery pack, but Prius PHEV owners get the smaller amount ($2,500). Still, the Prius overall will cost about $2,000 less after you figure in the tax credits.

Winning the hearts and wallets of consumers could come down to one number – but will it be 35 (as in the Volt’s estimated miles of electric range, per the EPA), or will it be 49 (as in the total MPG that the Prius will achieve in hybrid mode)?

At 37 MPG after the batteries are depleted, the Volt ain’t no Hummer or Escalade. And with 14 miles of electric range, the Prius PHEV offers much greater silent driving than the original Prius.

But which vehicle will cost more to drive based on how far you go between charges?

Assuming a gas price of $3.50 and electricity at 11 cents per kilowatt-hour, the Volt’s bigger battery makes it cheaper to operate as long as you drive 70 miles or less between charges. At distances of greater than 70 miles, the Prius PHEVs’ greater fuel economy as a hybrid makes it cheaper to operate.

This is one scenario, and the conclusions may change if the price of gasoline goes up or down, or depending on the cost of electricity in your neighborhood. Also, the calculations for both vehicles assume that the gas engine is not engaged until the full electric driving range is completed, which may not be true depending on driving conditions and driver behaviors.

However, the graph illustrates that for most trips (<70 miles in between charging), primarily driving on electric power makes the Volt cheaper to operate.

Photo by BrainThought/Wikimedia