The Google RechargeIT study just went one step farther in testing their plug-in hybrid cars. By setting up a controlled test of their fleet of cars, they were able to produce a remarkable 90+ mpg.
RechargeIT Blog: Our plug-ins perform: 90+ MPG
We were curious to see how the cars would perform under controlled conditions - and how they would stack up against other conventional automobiles typically found in U.S. households. With that, the RechargeIT Driving Experiment was born!
In total, it took just over seven weeks to complete all the trips in all the vehicles. And with the results in, our plug-ins did great, with the Priuses getting more than 90 miles per gallon. The PHEVs not only greatly outperformed the average American fleet fuel economy of 19.8 MPG, they did significantly better than the standard hybrids – 53% fuel economy improvement for the plug-in Ford Escape and 93% improvement for the plug-in Prius.
The rechargeit experimental fleet of plug-in hybrid cars, up till now, was not achieving very good results. At 60 mpg or so, their mpg numbers could be matched by carefully driving an unmodified Prius. The problem, according to the researchers at google, was the short range trips. The employees were taking the cars out for their daily commute, which were pretty short. Since the cars would start up the gas engines at the beginning of every trip to power up the internal systems. Since the vehicles aren't traveling that far, the proportion of gas running time was still higher than most people would see.
Thus, the team decided on a 7 week experiment. They created 38 routes, 12 city routes of 1 to 30 miles, 14 city/highway routes of 7-60 miles and 12 highway routes of 15 to 92 miles surrounding the Mountain View headquarters where the experiment was taking place. They sent out each of their cars 257 times across those 38 routes for a total distance of 2228 miles.
They randomly assigned cars and 5 professional drivers to the trips, although they did control the order of the trips so all vehicles completed the city trips first, then the combined, then the highway trips.
They note the weather was pretty mild (in general) and so the heaters were never used, and the A/C was used only occasionally. Also the terrain was fairly flat.
One last (important) note, each plug-in car had to be 'sufficiently charged' before a driver could take it out on it's next trip. In the real world, you won't have that luxury.
Not surprisingly, the Toyota Prius Plug-in outran the competition in mpg numbers. Especially in the city routes, where they hit 115 mpg and they could take advantage of 1) the full charge, and 2) regenerative braking. On highway routes, the results for the PHEVs were a more modest 68 mpg. The Ford Escape plug-in hit 45 mpg in city driving, but was actually better at highway driving at 51 mpg. At the end of the day, the Ford Escape plug-in matched up pretty evenly with the unmodified Prius which got an average mpg of 48 mpg.
You can read up on the results and methodology by following the link.
Overall, I'm impressed by the test. They tried to control for what they could and, aside from allowing the battery to fully recharge for the plug-ins, treated each car the same. The drivers were professionals, but weren't trained on how to drive the hybrids. Someone who had more experience in driving hybrids, who knew how to hypermile, might make the results even more lopsided.