Another bit of news is that Consumer Reports will use MPGe (miles per gallon energy equivalent) when it tests plug-in and alternative fuel vehicles in the future. The press release does not explicitly say Consumer Reports will use the X Prize's criteria, but the X Prize's Carrie Fox told us that, "The plan, and it's still a plan, is for them to use the MPGe standard we've come up with." You can read an excerpt from the current official rules describing the MPGe calculations after the jump or read the whole ruleset in PDF.
[Source: Auto X Prize]
From the Automotive X Prize (page 29 of this PDF):
Measuring Fuel Economy (MPGe) All energy sources used to propel PIAXP [Progressive Insurance Automotive X Prize] vehicles will be measured to generate fuel economy compared to miles per gallon of unleaded gasoline (MPGe, see above). The amount of fuel consumed on board will be measured at the end of each race stage by mass for liquid fuels and by temperature and pressure readings from gaseous fuels. The amount of electricity consumed will be measured from the plug (AC) to return the vehicle to the state of charge it started the stage with. AC electricity will be converted to BTUs at a rate of 3412 BTU/kWh and added to the energy content of the consumable fuel used for each race stage. The total number of BTUs will be divided by the energy content in the gasoline used in the PIAXP (approximately 112,000 BTUs per U.S. gallon) to get gallons of gasoline equivalent (GGE). The GGE used for each stage will then be divided into the miles of the stage to produce the MPGe fuel economy result for each stage. This general approach will be used in all on-road and on-track stages.
Procedures for measuring fuel economy during the chassis dynamometer stage are different.