Our fleet

As part of our mission to fully evaluate the usefulness of plug-in hybrid technology, RechargeIT has created a test fleet of cars. We collect and make publicly available data on the performance of these vehicles. The fleet currently consists of standard hybrid Prius cars as well as eight Priuses that have been retrofitted to become plug-in hybrid vehicles. You can see how the test fleet is performing below under real world conditions, with hundreds of different drivers in a variety of driving conditions. Read more about our methodology and the numbers behind the calculations.

The plug-in hybrid vehicles currently in the fleet are using the Hymotion/A123 production plug-in hybrid kit. Prior to October 2008, we were testing earlier prototype versions of the Hymotion system in both the Toyota Prius Hybrid and the Ford Escape Hybrid.

Please note that the data for specific vehicles can be significantly different even for vehicles of the same type. In particular, those vehicles that were part of the RechargeIT Driving Experiment will show significantly higher MPG numbers than the other fleet vehicles due to differences in drive cycles compared to GFleet driving. For more information, please see this FAQ.

For reference, the vehicles used in the RechargeIT driving experiment were Makalu (Escape); Tikal (Escape plug-in); Kilimanjaro (Prius); and Comoe & Great Barrier Reef (Prius plug-ins).

 

Model

MPG

Wh/mile

CO2e lbs/mile

Our Cars

Toyota Prius

40.1

—

0.588

Alhambra
Angkor

Toyota Prius Plug-in

57.6

131.5

0.474

Baikal
Comoe
Galapagos
Garamba Reloaded
Googler01
Great Barrier Reef
Kilimanjaro Reloaded
Machu Picchu
Platano

Methodology

All of these cars are outfitted with data recording devices that track technical and environmental performance, use patterns and charging history. Above, you can see the actual data which is uploaded from the vehicles. Both electricity and gasoline consumption data is being used to calculate the total energy use for each vehicle to get "real world" performance data on these cars. In order to compare this data to other cars under similar conditions, we have equipped existing conventional hybrids with the same data recording devices. With this data, we are be able to measure more realistic MPG efficiency of plug-ins over conventional hybrid vehicles.

The system to collect data from our fleet consists of an embedded computer running Linux, a wireless data card, a GPS and an AC power monitoring device to monitor charge power. The embedded computer is connected to the vehicle's CANbus (a data bus present in all new vehicles), and collects relevant data such as speed, distance driven, fuel use, and the vehicle's high voltage battery parameters. Information from the extended hybrid battery, such as voltage, current, charge state and battery temperature, is also accessed and archived for data analysis.

During charging, the system monitors and records the AC charge power. GPS is used by the fleet manager to track the vehicle's location, and in the future may be used to plot vehicle data against altitude. All this data is periodically uploaded to our servers via a wireless connection where it is further post-processed and used to refresh the data displayed on our website. In addition to the data collected on board, we use a fleet fueling card that accurately records the amount of fuel used by each car which is then uploaded to our servers and used for the miles-per-gallon calculation.

Once all the data is uploaded to our servers, any necessary calculations are done (such as calculating CO2), and the data is graphed and displayed on our website. Data is available at the fleet level, individual car level and charging event/trip level.

FAQ

Why do the MPG numbers for the Driving Experiment differ from the observed MPG for the GFleet cars?

We think that the numbers reported in the Driving Experiment are closer to the numbers drivers of plug-ins would experience but still want to publish the data from our GFleet cars. There are many factors that affect the MPG achieved by our plug-in hybrids, some rather dramatically:

  1. Our plug-in vehicles are plug-in conversions, and use a hybrid system that was not designed for plug-in use. We anticipate that clean-sheet plug-in hybrid vehicles like the upcoming Chevy Volt and Toyota Prius will deliver higher overall efficiency and less variability in fuel consumption.
  2. Driving patterns for a corporate car that is driven by several different people a day is not always representative of "normal driving patterns." A disproportionate number of GFleet vehicle trips are very short. Although these trips could be driven with little use of the gas engine, the gas engine automatically starts to warm up the emissions equipment, lowering fuel economy.
  3. The effect of differences in driving style is quite noticeable in plug-in vehicles. Google employees driving the GFleet cars are not familiar with how best to drive the car to maximize fuel efficiency. The Driving Experiment employed professional drivers who tended to drive the vehicles more conservatively. We think that individual owners of plug-in vehicles will have the incentive to learn how to drive their car in a way that is most fuel efficient.
  4. The GFleet vehicles are sometimes not sufficiently charged before a trip, either because the drivers forgot to plug in the vehicle or there was insufficient time to fully charge the battery between trips.
  5. We recently swapped out the Hymotion package in the GFleet cars. While this brought the vehicles into compliance with CARB emissions standards, it also led to an overall reduction in the fuel economy of the fleet.