Without access to the actual method that the EPA is tentatively going to apply to plug-in vehicles (we have requests for clarification out to the EPA), all that GM's Dave Darovitz would tell us is that the number is "based on city cycles and we're not really talking in detail yet." Instead, the press release says that:
Frank Weber, vehicle chief engineer for the Volt, told AutoblogGreen that the EPA's method takes into account the two extremes: People who plug in every chance they get and therefore barely ever need gasoline and people who never plug in (if you're buying a Volt and never plug it in, we'd like to offer you a bridge or two. Call us). By figuring out what the average driver will do with the Volt, the EPA has declared that 230 mpg is reasonable. Weber said, "The number is in the ballpark, it is not unrealistic. The moment you are driving shorter trips, or you go on longer trips and look at your average fuel economy, this number is achievable."Under the new methodology being developed, EPA weights plug-in electric vehicles as traveling more city miles than highway miles on only electricity. The EPA methodology uses kilowatt hours per 100 miles traveled to define the electrical efficiency of plug-ins. Applying EPA's methodology, GM expects the Volt to consume as little as 25 kilowatt hours per 100 miles in city driving. At the U.S. average cost of electricity (approximately 11 cents per kWh), a typical Volt driver would pay about $2.75 for electricity to travel 100 miles, or less than 3 cents per mile.
Keep in mind, that 230 mpg number is only valid in city driving, though GM claims that the Volt's combined mpg rating will still be in the triple-digit range. Though the EPA has yet to finalize its methodology, we have come across a calculation that makes sense. According to a commenter on TTAC.com, the EPA would first drive a PHEV with a full charge until it reaches a charge-sustaining mode, after which it completes a normal cycle of 11 miles. The Volt, therefore, would presumably go 40 miles before activating charge-sustaining mode, and then travel another 11 miles for a total of 51 miles. Thus, GM can claim the Volt will achieve 230 mpg based on 51 miles of driving during which only .22 gallons of fuel would be used. Likewise, if we know the Volt would use .22 gallons of fuel while traveling 11 miles in charge-sustaining mode, we can calculate that it would achieve 50 mpg while traveling with the generator on.
However, as you can read in this detailed PDF from NREL, there is much more to think about in calculating the fuel economy of a PHEV than simply how far it can go on a single charge and then what its "regular" mpg rating is. We'll just have to wait until the EPA finalizes its methodology for testing these types of vehicles before we can say for certain how GM arrived at the magic number of 230 mpg.
[Source: GM, NREL]
Chevrolet Volt Expects 230 mpg in City Driving
* First mass-produced vehicle to claim more than 100 mpg composite fuel economy
* Tentative EPA methodology results show 25 kilowatt hours/100 miles electrical efficiency in city cycle
* Plugging in daily is key to high-mileage performance
WARREN, Mich. - The Chevrolet Volt extended-range electric vehicle is expected to achieve city fuel economy of at least 230 miles per gallon, based on development testing using a draft EPA federal fuel economy methodology for labeling for plug-in electric vehicles.
The Volt, which is scheduled to start production in late 2010 as a 2011 model, is expected to travel up to 40 miles on electricity from a single battery charge and be able to extend its overall range to more than 300 miles with its flex fuel-powered engine-generator.
"From the data we've seen, many Chevy Volt drivers may be able to be in pure electric mode on a daily basis without having to use any gas," said GM Chief Executive Officer Fritz Henderson. "EPA labels are a yardstick for customers to compare the fuel efficiency of vehicles. So, a vehicle like the Volt that achieves a composite triple-digit fuel economy is a game-changer."
According to U.S. Department of Transportation data, nearly eight of 10 Americans commute fewer than 40 miles a day http://tinyurl.com/U-S-DOTStudy .
"The key to high-mileage performance is for a Volt driver to plug into the electric grid at least once each day," Henderson said.
Volt drivers' actual gas-free mileage will vary depending on how far they travel and other factors, such as how much cargo or how many passengers they carry and how much the air conditioner or other accessories are used. Based on the results of unofficial development testing of pre-production prototypes, the Volt has achieved 40 miles of electric-only, petroleum-free driving in both EPA city and highway test cycles.
Under the new methodology being developed, EPA weights plug-in electric vehicles as traveling more city miles than highway miles on only electricity. The EPA methodology uses kilowatt hours per 100 miles traveled to define the electrical efficiency of plug-ins. Applying EPA's methodology, GM expects the Volt to consume as little as 25 kilowatt hours per 100 miles in city driving. At the U.S. average cost of electricity (approximately 11 cents per kWh), a typical Volt driver would pay about $2.75 for electricity to travel 100 miles, or less than 3 cents per mile.
The Chevrolet Volt uses grid electricity as its primary source of energy to propel the car. There are two modes of operation: Electric and Extended-Range. In electric mode, the Volt will not use gasoline or produce tailpipe emissions when driving. During this primary mode of operation, the Volt is powered by electrical energy stored in its 16 kWh lithium-ion battery pack.
When the battery reaches a minimum state of charge, the Volt automatically switches to Extended-Range mode. In this secondary mode of operation, an engine-generator produces electricity to power the vehicle. The energy stored in the battery supplements the engine-generator when additional power is needed during heavy accelerations or on steep inclines.
"The 230 city mpg number is a great indication of the capabilities of the Volt's electric propulsion system and its ability to displace gasoline," said Frank Weber, global vehicle line executive for the Volt. "Actual testing with production vehicles will occur next year closer to vehicle launch. However, we are very encouraged by this development, and we also think that it is important to continue to share our findings in real time, as we have with other aspects of the Volt's development."
Chevrolet is one of America 's best-known and best-selling automotive brands, and one of the fastest growing brands in the world. With fuel solutions that go from "gas-friendly to gas-free," Chevy has nine models that get 30 miles per gallon or more on the highway, and offers three hybrid models. More than 2.5 million Chevrolets that run on E85 biofuel have been sold. Chevy delivers expressive design, spirited performance and provides the best value in every segment in which it competes. More information on Chevrolet can be found at www.chevrolet.com. For more information on the Volt, visit http://media.gm.com/volt/.
General Motors Company, one of the world's largest automakers, traces its roots back to 1908. With its global headquarters in Detroit, GM employs 235,000 people in every major region of the world and does business in some 140 countries. GM and its strategic partners produce cars and trucks in 34 countries, and sell and service these vehicles through the following brands: Buick, Cadillac, Chevrolet, GMC, GM Daewoo, Holden, Opel, Vauxhall and Wuling. More information on the new General Motors Company can be found at www.gm.com.