The 2020 Toyota Prius Prime plug-in hybrid gains some important functionality, even though some of the key specifications for range and efficiency haven't changed.

The most important improvement, perhaps, is that the Prime now offers a third seat in the center-rear, making it a five-passenger car. Previous versions had only four seats.

The second big improvement is Apple CarPlay capability, as Toyota recently included on the 2019 Toyota Camry and Sienna. Owners can also use Amazon Alexa to make in-car purchases such as music downloads or to access the car from home, for example to query the state of charge or the fuel level, or to turn the car on to preheat or cool it.

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More minor updates that may be meaningful to some buyers include new USB charge ports for the rear seats, sun-visor extensions for those morning and evening commutes with the sun coming in the side, and black plastic interior accents that replace the previous polarizing white. Relocated seat-heater buttons are also much more convenient. 

In addition to all the new equipment, Toyota has updated the Prius Prime trim levels to follow its other models, as it did with the standard Prius earlier this year.

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Following long-established convention for Toyota, the new trim lines will start with the LE at $27,600 and move up through XLE for $29,500 and Limited grade at $33,500, replacing Plus, Premium, and Advanced.

Toyota did not specify what new equipment may be included on what trims, but the current Premium adds integrated navigation, a power driver's seat, and leatherette upholstery; while the Advanced model adds a large 11-inch center display, blind-spot monitoring with rear cross-traffic assistance and self-parking, and a head-up display, a heated steering wheel, automatic rain-sensing wipers, auto-dimming mirror, and additional remote-connected apps, including safety notifications.

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In any case, the 2020 Prius Prime will still have 25 miles of electric range from its lithium-ion battery pack. The Prime includes a button to select among standard mode, which maximizes efficiency automatically; hybrid mode, which preserves the charge in the battery for later use; or EV mode, which uses only the battery until the charge is depleted.

Once the charge is gone, the Prime is rated at 54 mpg in combined city and highway driving on gasoline, the highest of any plug-in hybrid on the market.

Unlike the standard 2020 Prius, the Prime is not available with all-wheel drive. It is expected to hit the market by July.