Both cars are plug-in hybrid vehicles made by major automobile manufacturers. A plug-in hybrid car is one where there is both a gasoline engine and electric motor on-board, and that you can plug-in to recharge the battery pack separately from the gasoline engine. Plug-in hybrids also carry a larger battery pack than on regular (non-plug-in) hybrids, and the larger pack makes for a longer range of electric-only driving. For those of us who want to ease gasoline out of our lives, plugging in the car to recharge the battery pack is the way to go.
While we can now go with pure electric cars from Nissan, Mitsubishi and soon Ford, having a gasoline engine on-board, acting as a generator, is a pragmatic solution to the range consideration due to the 100 mile or so range of pure electric cars. In around-town driving the plug-in hybrid owner will plug in, recharge the battery pack, and drive on electric power until the pack is depleted, at which time, the car fires up the gasoline engine to recharge the battery pack, and if done well the switch-over is seamless. The plug-in hybrid concept is old, and is fairly obvious to any electric car owner who wants more range and is willing to burn fuel to get that range. The first plug-in hybrid was built by Dr. Ferdinand Porsche over 100 years ago, it had four hub motors (motors embedded in the wheels), used the gasoline engine purely to recharge the battery pack, and set speed records in its time.
With that background information let's now turn to a couple modern cars, the 2012 Toyota Prius Plug-in and 2012 Chevy Volt.
The Chevy Volt has a 15 kilowatt-hour battery pack that gives a 35-50 mile electric-only driving range depending on conditions (the EPA rating is 36 miles electric-only range). The 149 horsepower electric motor can power the Volt at up to 100 miles/hr. The 1.4 liter 83 horsepower gasoline engine acts primarily as a generator, but the transmission is configured so the engine kicks in at high speed to help drive the car. The gasoline engine requires premium fuel, and with the 9.3 gallon gas tank you have a 325 mile cruising range in gasoline mode, and a 35-40 miles/gallon fuel efficiency. The total cruising range is 407 miles and in electric mode the Volt gets 93-95 miles/gallon (equivalent) fuel efficiency.
The Prius Plug-in has a 4.4 kilowatt-hour battery pack that gives 12-15 miles electric-only driving range. The 80 horsepower electric motor is used at speeds below 62 miles/hr, and at higher speeds both work together. The 1.8 liter 98 horsepower gasoline engine acts as both electric generator and drive motor, with a transmission allowing a blending of both power plants to drive the wheels, with a net system 134 horsepower. With a 10.6 gallon gasoline tank, in gasoline/hybrid mode the Prius Plug-in is rated for 49 miles/gallon, and a combined electric-hybrid 87 miles/gallon (equivalent) fuel efficiency. The Prius Plug-in has not been EPA certified, so these numbers are based on Toyota's estimate.
The more powerful drive train on the Chevy Volt (149 horsepower electric) is a clear advantage over that in the Prius Plugin (98hp gas, 40hp electric, 134 hp combined).
Repeated studies in the U.S. including US Department of Transportation shows the majority of drivers go 40 miles or less per day. This tells us a Chevy Volt owner will spend more days without burning gasoline, than will the Prius Plug-in owner. GM knew these figures and designed the Chevy Volt to give enough electric-only range to satisfy the majority of daily driving needs. Toyota on the other hand wanted to hit a more affordable price point, to reach more car buyers many of whom are price sensitive. This means the Prius Plug-in has a smaller battery pack, and a smaller MSRP, but has only a 12-15 mile electric-only range. This means the Prius Plug-in owner will be seeing their gasoline engine turn on more often than will the Chevy Volt owner.
Whether the Volt or the Prius Plug-in has the advantage here depends on your point of view. If your interest is the highest miles/gallon at the best price, and you don't care much about electric-only range, then the Prius Plug-in has the advantage. If your interest is longest electric-only range with the gas engine to cover longer trips, and you're able to swing the extra dollars, then the Volt has the advantage.
The Chevy Volt battery pack is a T-shape that creates a central tunnel going down the passenger cabin. The battery tunnel is tall enough that the back seat can only hold two people, meaning the Volt can hold four people total. The Prius family all will hold five people like most other sedans. In this case the Prius Plug-in and most other sedans have an advantage over the Volt, because they can seat an additional person.
The Prius Plug-in has a 21.6 cubic foot cargo area, while the Chevy Volt has a 10.6 cubic foot cargo area. Both use a "liftback" arrangement giving good access to the trunk area, however clearly the Prius has the advantage in cargo volume.
Because the Prius Plug-in battery pack is so much smaller than the Chevy Volt, charging time is very fast. For the Prius, charging time is 1 1/2 hrs at a charging station, or three hours on a 120 volt outlet. The Volt, on the other hand, takes 10 hours to charge on a 120 volt circuit, or four hours at a charging station. The larger battery pack gives a longer electric range, but also takes longer to recharge. Clearly the shorter charging time of the Prius is an advantage, but it's also a trade-off for a shorter electric range which may be a disadvantage depending on your needs.
The Prius Plug-in, as part of the Prius family, has over 10 years of history and consumer awareness. This should give it an advantage over the Chevy Volt, when it goes on sale, because the public is already looking to the Prius line for high fuel efficiency. GM, on the other hand, has a task ahead of it to educate the public what the Volt is, what the advantage of a plug-in hybrid is over a regular hybrid, and even the advantage of a longer electric-only range over a short electric-only range.
The two largest differences between the Prius Plug-in and the Chevy Volt is the price and the electric-only range. The Volt gives you a longer electric range, at a bigger price. That bigger battery pack is the key to both these attributes. The price premium paid for a Chevy Volt over the Prius Plug-in may be worth it to you, depending on your interests and situation, but if you don't understand the advantages of each will you understand why you should pay the higher price for the Volt? Suppose your daily commute is 33 miles round trip. With the Prius Plug-in you'll drive some of your miles each day using the gasoline engine, even if you have a charging station at your office. Contrarily, the Volt could do that on electric drive, even if you do not have a charging station at the office. The Volt owner will end up saving a lot of money because electricity is a cheaper "fuel" than gasoline. If GM cannot convey the tradeoffs between range, utility and cost, GM may end up losing to Toyota's Pruis Plug-in.
The Chevy Volt has been on sale for well over a year, and is now available nationwide, and its MSRP is $39,500. The Prius Plug-in goes on sale in March, and initially will be available in a limited number of states, and its MSRP is $32,000. As we just said, whether the Prius or the Volt has the price advantage depends on your situation and needs. However, the Chevy Volt qualifies for government incentives that do not apply to the Prius Plug-in, and the $7500 tax credit erases the price difference.
Which of these cars wins over the other? It depends. The Prius Plug-in has clear advantages in brand awareness and price, except the $7500 tax credit for the Volt makes up for the price difference. The Chevy Volt has a clear advantage in electric range, and with the more powerful drivetrain. That longer electric range could make up for the price premium depending on how much gasoline you end up burning with the Prius.