The 2017 Toyota Prius Prime is a considerably better car than a few electric-car fans had feared.
In fact, with an EPA-rated range of 25 miles (more than projected) and energy efficiency so high—at 133 MPGe—that it matches the BMW i3 with all its whizzy advanced technology, it’s a very viable plug-in hybrid choice.
[EDITOR'S NOTE: At the time this piece was written, the efficiency figure projected by Toyota for the Prius Prime was 124 MPGe. Toyota subsequently released the official EPA ratings, in which the efficiency figure was 133 MPGe—making the Prius Prime the most energy-efficient vehicle sold in the U.S. bar none. We have updated the article accordingly.]
And it all has to do with one little design choice made by the plug-in Prius design team.
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That decision was to default the car into electric-only mode if its battery has any charge remaining (above that needed to operate as a conventional Prius hybrid, which it does after the battery is depleted).
It’s a simple software command, but it turns the Prius Prime from a hybrid into an electric car over its first 20 or 25 miles. That means it’s not the engine-and-electric-combined vehicle that many expected it to be.
And it sets the car apart from every other plug-in hybrid except the Chevrolet Volt, which also operates entirely in electric mode until its battery capacity is depleted.
The rest of the mass-priced plug-in hybrid competitors—versions of the Ford Fusion, Hyundai Sonata, and soon the Kia Optima—all kick on their engine when maximum power is required.
Sure, their drivers can choose an all-EV mode, but the Prius Prime flips that around, requiring drivers to take an action if they don’t want electric-only operation.
That’s key. And it’s nothing remotely like the driving behavior of the Prime’s predecessor, the now-discontinued 2012-2015 Prius Plug-In Hybrid.
That car’s 11-mile electric range was so low, and its 60-kilowatt (80-horsepower) electric drive motor so weak, that it sometimes seemed that even breathing heavily would kick on the engine.
Toyota managed to sell 75,000 Prius Plug-In Hybrids globally, a large number of the 42,000 U.S. sales on the strength of the California carpool-lane stickers it qualified for.
But just as the fourth-generation conventional Prius hybrid is a far better car to drive than its predecessor, the Prius Prime is a much better plug-in hybrid than the first plug-in Prius.
Better yet, in two different conversations with Toyota executives over the last 12 months, it appears that continuing advances in lithium-ion cell capacity could produce a longer electric range during this car’s six- or seven-year life.
The Prime's lithium-ion battery, located under and behind the rear seat, remains air-cooled, but its 8.8-kilowatt-hour capacity is double that of the first-generation plug-in Prius.
And its EPA-rated range of 25 miles is higher than the 22 miles projected by Toyota when it unveiled the Prius Prime in March.
We first drove the 2017 Toyota Prius Prime Advanced on a 20-mile loop through the hills around scenic Ojai, California.
The weather, in the low 90s, was good for an electric car, but we kept the air conditioning on low throughout our drive.
We completed the 20-mile loop, at speeds ranging from 25 to 60 mph, and still had about 5 miles remaining on the car—though the route contained very little high-speed driving.
Still, in mixed low- and high-speed use, we think the 25 miles is a fair estimate of the Prime's real range. With gentle driving at lower speeds, some owners will likely see 30 miles or more.
That compares to 22 miles for the this year's Ford Fusion Energi, 27 miles for the Hyundai Sonata Plug-In Hybrid, and of course 53 miles for the Chevrolet Volt.
When the battery is depleted and the Prius Prime turns into a slightly heavier version of the conventional hybrid Prius, it is rated at 54 mpg combined (55 mpg city, 53 mpg highway).