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Prius Plug-in Versus Volt: Which Costs Less to Drive?

John Gartner — October 17, 2011

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. 

6 Responses to “Prius Plug-in Versus Volt: Which Costs Less to Drive?”

  1. John C. Briggs says:

    Interesting analysis but in places like California, electricity is significantly more expensive which will probably make the Prius better value. Also, below 15 mile trips, the Prius is probably better as well.

  2. Mariordo says:

    Very useful, but why there is an inflection point for the Prius PHEV at 30 miles? The slope should be constant after 15 miles when the battery is depleted.

  3. Mariordo says:

    I forgot, and the inflection point for the Volt should be at 35 miles not 30 mi, again, once the battery is depleted.

  4. The inflection point at 30 miles is due to the x-axis interval change from 15 to 30.

    I created a new graph with 5 miles interval. I also considered the price difference between regular and premium gas.

    Even if I use a conservative 10 miles EV range for Prius Plugin, the two lines interests at 55 miles mark at $3.48.

    See the graphs and spreadsheet with calculations at:
    http://priuschat.com/forums/toyota-prius-phv-plug-in/99125-prius-plug-in-versus-volt-costs-less-drive.html

  5. Thomas says:

    Gartner writes “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.”

    What he ignores is the simple fact that it is almost impossible to drive the Prius on the freeway without engaging the gas engine, and it is difficult to stay electric only even at lower speeds.

    The Volt is all electric until the battery is drained regardless of how it is driven. The Prius battery does not have enough power to drive the car by itself except under moderate acceleration and speeds.

    Every review I have seen asserts that at speeds of around 50-60mph on level ground the car will switch to gas power regardless of how you drive it. So essentially anyone who commutes at highway speeds will get the posted gas mileage with little savings from the battery.

  6. Marc says:

    Very good analysis. The Volt takes premium unleaded fuel while the Prius is regular unleaded. The inflection point at 30 is the result. That’s why beyond 35 miles of driving, the Prius starts catching up on savings. Both great cars.

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