Plug In Conversion Group has release a software update that will allow converted plug-in Priuses to travel up to 70 mph in electric only mode.
Toyota programming had previously limited the electric only speed to 34 mph, but by breaking the programming code, PICC has more than double the speed allowing for highway commutes that don't use a drop of gas.
The upgrade also increases the highway mpg of converted Priuses to 170 mpg. The math used to calculate the number is fuzzy, but legitimate. Calculations are done to determine estimated gallons of gas used to create the electricity that charged the battery. The system is said to be capable of 25 miles on electric only power at highway speed.
The cost of the conversion and software upgrade is not cheap. First start with a Prius at $22,000, add plug-in capability at $12,500, and a software upgrade of $2,500 to get a total cost of $37,000.
The cost puts its up in the expected range of the Volt, but the Volt receives a $7,500 rebate, the converted Prius does not.