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NREL's Prius Hits 100 Miles per Gallon

June 20, 2008

Photo of a small four-door car, viewed from the side, which is parked in front of a field of solar panels with jagged mountains in the background. The car is painted with images of a corn stalk and a wind turbine with 'Plug-In to Renewable Energy' written on the side panel.

The batteries in NREL's modified Toyota Prius can be recharged with power from solar panels or wind turbines, so the car can travel about 60 miles on nearly all renewable electricity.

Photo of a man, wearing a gray suit, green shirt and green tie, who is talking to three men, in suits, with their backs to the camera. The man is facing the camera and has his left hand resting on the hood of NREL's research plug-in hybrid vehicle, which is parked in a lot.

NREL Senior Engineer Tony Markel explains how a plug-in hybrid works. Research results will help automakers bring these cars to market.

Drawing of a red car, labeled How a Plug-In Hybrid Works. The red car has been cut away to reveal an engine under the hood on the left; an electric motor, under the hood on the right; an electric battery pack that's long narrow and gray running right to left across the middle of the car; a fuel tank in the right rear of the car and a battery recharge plug (looks like a three-prong household plug) coming from the left rear of the car.  The electric battery pack is connected by wires to the electric motor.

The battery pack alone can power the plug-in hybrid for about 60 miles. The batteries are recharged when the car is plugged in, when the engine is running or during braking. At speeds under 35 mph, the car can run on the electric motor alone. When more power is needed, the engine and the electric motor work together.

A hybrid passenger car modified by NREL researchers is cruising at 100 miles per gallon (mpg) and generating international notice as fuel prices soar to record levels.

The experimental plug-in version of a 2006 Toyota Prius sedan runs the initial 60 miles mostly on battery, with the remainder achieved under engine power.

The sedan's performance more than doubles the fuel economy of a standard Prius, which is rated at 48/45 mpg. And, it's a five-fold improvement over the 20 mpg average that passenger cars and light trucks in the U.S. achieved in 2007.

How the Plug-In Hyrbid Works

The standard Prius runs on electricity at low speeds, then the batteries and the gasoline engine share the work. The batteries recharge automatically as the car operates.

NREL researchers added several features to the plug in Prius to break the 100-mpg barrier:

  • A plug to recharge its batteries directly from the utility grid using a standard 110-volt electrical outlet,

  • A larger lithium-ion battery that allows the car to operate on electricity for longer trips at speeds up to 35 mph, and

  • A rooftop solar panel that charges the battery while the car is driving or parked outdoors, adding five miles to the vehicle's range.

"The stored power in the battery does a great job of displacing petroleum," said Tony Markel, a senior engineer with the Vehicle Systems Analysis Group. "Most people's daily commute is about 30 miles, so this car would run virtually on battery for their entire drive."

What the Plug-In Hybrid Costs

The NREL Prius is a unique research prototype, and is not available to the public. It cost about $70,000 — the cost of the standard Prius plus $42,500 for the modifications.

The improved fuel economy would save more than $500 per year over the standard Prius, and potentially reduces the vehicle's greenhouse gas emissions to less than two tons per year.

Markel said Detroit automakers and Xcel Energy, Colorado's biggest utility are interested in how NREL's plug-in hybrid could be produced affordably.

Research results have been included in a couple of papers published by NREL staff. Markel said that his team will be testing a different battery pack in the car soon, and that the Prius will be used to help explore options for recharging with renewable electricity, such as solar and wind.

Other Hybrid Vehicle Studies at NREL

Markel's results are consistent with a 2007 computer modeling study by Xcel and NREL that showed how plug-in hybrid vehicles would cut CO2 emissions in half and save owners $450 apiece in annual fuel costs, without requiring a significant utility expansion.

NREL also is collecting and analyzing vehicle performance data from 50 UPS hybrid diesel step delivery vans powered by an Eaton Corp. electric hybrid propulsion system. The 12-month study in Dallas and Phoenix is scheduled to end in August.

Learn more about NREL research in Plug-In Hybrid Electric Vehicles.

Learn about the basics of Plug-In Hybrid Electric Vehicles.