Real-world plug-in hybrids disappoint on efficiency, with a recent test in Seattle demonstrating that 14 customized plug-in hybrid Toyota Priuses did not do much better than standard Priuses:
Try 51 miles per gallon, city and highway combined. Not counting the cost of the electricity.
It’s what 14 plug-in Priuses averaged after driving a total of 17,636 miles. The pilot project is one of the few in the nation to subject plug-in hybrid cars to regular motor-pool duty, as opposed to being driven by hypermilers or alt-energy enthusiasts.
Google’s own fleet hasn’t done much better:
Their Ford Escape hybrids are averaging 28.6 mpg while their pluggable versions of the Escape hybrd get 37.7 mpg for a 32% improvement. Not earth shattering. Their conventional Prius hybrids get 42.8 mpg while their pluggable Priuses get 54.9 mpg for a 28.3% improvement Again, not exactly the end of the oil era. Google breaks out the numbers by car. The best has done 60.5 mpg. But if you look at single day results you can find cars hitting 107 mpg.
Why these disappointing results? A fleet car could get driven a lot in a day and run down its batteries. To maximize the benefit of a pluggable hybrid one really need to drive almost the battery’s range each day but no more. Someone who happens to commute a distance that is a little less than the range of a hybrid’s battery is the best candidate to get maximal benefit.