The 2017 Toyota Prius Prime plug-in hybrid's tenure as the most energy-efficient car on sale in the U.S. turned out to be short.

The Toyota recently took the title of most energy-efficiency vehicle available in the U.S. away from the BMW i3, which had held it since 2014.

But now there's a new kid on the block.

DON'T MISS: Hyundai Ioniq electric car offered on 'Ioniq Unlimited' subscription model

Along with an EPA-rated range of 124 miles, the 2017 Hyundai Ioniq Electric has an EPA rating of 136 MPGe combined.

That beats the 133 MPGe of the Prius Prime when operating in electric mode, as well as the 124 MPGe of the most efficient version of the i3.

That i3 rating is earned by i3 models fitted with the 22-kilowatt-hour battery pack that has been available since launch.

2017 Toyota Prius Prime Premium

2017 Toyota Prius Prime Premium

For the 2017 model year, BMW also introduced a larger, 33-kWh pack, which brings a slightly lower efficiency rating of 118 MPGe but an electric range of 114 miles, up from 81 miles.

(Miles Per Gallon Equivalent, or MPGe, is a measure of how far a car can travel electrically on the same amount of energy as contained in 1 gallon of gasoline.)

The Ioniq's efficiency rating also puts it well ahead of the 2017 Nissan Leaf, which is rated at 112 MPGe, with a 107-mile range.

ALSO SEE: 2017 Hyundai Ioniq preview

While the Ioniq—which will also be available with hybrid and plug-in hybrid powertrains—tops the 2017 Chevrolet Bolt EV's 119 MPGe combined efficiency rating, it can't match the Chevy's 238-mile range.

The Bolt EV is expected to be the first of multiple mass-market 200-mile electric cars, which means the Ioniq Electric could soon be leapfrogged.

That includes the 215-mile, $35,000 Tesla Model 3—which Tesla says will start production at the end of next year—as well as a second-generation version of the Leaf, expected to debut sometime over the next 18 months.

2017 Hyundai Ioniq Electric

2017 Hyundai Ioniq Electric

Ahn Byung-ki—director of Hyundai's eco-vehicle performance group—said recently that Hyundai views the Ioniq's 124-mile range as adequate for now, but that the carmaker does plan to extend it.

A 200-mile version of the Ioniq Electric will arrive by 2018, Ahn said during a recent media event at Hyundai's Michigan technical center.

Ahn did not specify how Hyundai will increase the Ioniq Electric's range, but fitting a battery pack with a significantly larger form factor would seem to be difficult.

MORE: Hyundai Ioniq Electric car to get 200 miles of range 'soon'

Hyundai sited its battery under the rear seat, and between the rear wheels, not leaving much extra room, although the pack could be extended into the central tunnel.

The 124-mile Ioniq Electric will go on sale before the end of this year, along with the Ioniq Hybrid model.

The Ioniq Plug-In Hybrid will follow next year.


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