Plug-in hybrid electric vehicles (PHEVs) like the Toyota Prius Plug-in, Chevy Volt and Fisker Karma offer consumers appealing new options for boosting the fuel efficiency and eco-performance of their daily drivers. These versatile vehicles provide those who want an electric driving experience the flexibility needed for road trips and long commutes, quelling any concerns they might have about range anxiety.
As a quick refresher, conventional, grid-free hybrid electric vehicles, such as the Ford Fusion, Toyota Prius, Honda Insight and many others, enhance fuel economy by using electric motors to assist the gasoline engine in low-load situations like urban stop-and-go driving. The motors are powered by a smallish battery — for example, 1.4 kilowatt hours (kWh) in the Ford Fusion Hybrid — that collects energy otherwise lost during braking.
PHEVs build on these efficiency gains by using a larger battery that can be charged from the electric grid. As a result, PHEVs enable consumers to get around gas-free, running only on electricity, for tens of miles at a time when driving at moderate speeds.
The Toyota Prius Plug-in, earning an eRating 211, is based on the popular 3rd generation Prius and uses a 4.5 kilowatt-hour (kWh) lithium-ion battery. When EV mode is activated, this beefier battery offers an EPA-certified electric range of 11 miles at speeds below 62 miles per hour and moderate acceleration.
When not in EV mode or if the battery is depleted, the Prius Plug-in offers the same fuel economy as the grid-free Prius, an impressive 50 mpg combined. This miserly use of fuel is achievable because the both models share Toyota’s Hybrid Synergy Drive system, an ultra-efficient hybrid powertrain now proven in over three million vehicles on the road worldwide.
The Chevy Volt earns an eRating of 202. Taking a different approach to PHEV capability, General Motors’ engineered the Volt as an extended-range electric vehicle. It is designed to drive the wheels almost exclusively by electricity whether or not supplemented by the car’s gasoline engine. The sizing of the Volt’s electric drivetrain reflects this difference. Built into the vehicle is a T-shaped battery pack rated at 16.5 kWh, more than triple the capacity of the Prius Plug-in’s battery and able power the Volt for 38 miles on electric energy alone.
Chevy Volt owners report regularly exceed this EPA-rated range, and all together tallied over 100 million miles on electricity alone during the first two years since this first American-made PHEV was launched.
Paired with the Volt’s battery is a powerful 149 horsepower electric motor that is responsible for the majority of vehicle propulsion. Through a planetary gear set and series of clutches, the Volt’s 1.4 liter engine operates to help power the vehicle during high speed and brisk acceleration or when the battery gets depleted. When the engine is in action, the Volt earns a combined 37 mpg. Although impressive for a 3,781 pound compact car, that amounts to 13 fewer miles per gallon than the Prius Plug-in, which benefits from an ultra-efficient Atkinson cycle engine and lower vehicle mass.
Now earning an eRating of 113, Fisker’s 403 horsepower luxury sports sedan further proves that not all PHEVs are cast from the same mold. We first covered the Karma when its initial mileage ratings were announced in fall 2011. The Karma is also the only true “series” hybrid on the market, meaning that its range-extending engine never mechanically powers the wheels. All of the gasoline energy is first converted to electrical energy to run the motors and charge the battery. Two electric motors, located on the rear axle, are capable of twisting the tires with an amazing 959 pound feet of torque.
The Prius Plug-in, Chevy Volt and Fisker Karma offer consumers a taste of the advanced technologies manufacturers are developing to meet an ever-increasing need for higher efficiency. Other PHEV offerings on or about to enter the market for 2013 include Ford’s Fusion Energi and C-Max Energi, Honda’s Accord Plug-in Hybrid and Mitsubishi’s four wheel drive Outlander PHEV. Stay tuned for how these cutting-edge designs score on the AutoEcoRating scale.
|Make and Model||$MSRP||Specs||City / Hwy / Comb MPG |
|Toyota Prius Plug-in||32,760||134 hp hybrid drive, |
11 mile all electric range
|51 / 49 / 50 |
|Chevrolet Volt||39,995||149 hp electric drive,|
38 mile all electric range
|35 / 40 / 37 |
|Fisker Karma||103,000||403 hp electric drive,|
33 mile all electric range
|20 / 21 / 20|