The Hymotion by A123Systems is a PHEV (plug-in hybrid electric vehicle) module that has just rolled out that will enable Toyota Prius owners to achieve 100 mpg.
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A123Systems Hymotion Plug-In Conversion for Toyota Prius

V2 Green Technology Tested in Texas
V2Green of Seattle is collaborating with Austin Energy for Smart Charging of plug-in hybrid electric vehicles that will enable the grid to charge the PHEVs only during off-peak hours and only using renewable energy.

Visionary Vehicles EVX / LS Bricklin Collection PHEV
The Visionary Vehicles EVX / LS plug-in hybrid vehicle is set to compete with other luxury cars on price while achieving 100 mpg.

Plug-in hybrids: 100 miles per gallon or 59?
Plug-in hybrids have emerged as the favorite form of transportation for reducing greenhouse gases in the near term, but calculating their energy efficiency can be a little complicated.