Does anyone see problems with my math?

Plug in Hybrid electric vehicles are supposed to hit the market soon. Here is what I calculate for the cost of the equivalent of gallon of gasoline.

Gasoline is 125,000 BTU/gallon of which 20% is converted to mechanical energy. so 25,000 BTU = 26,376 KJ. 1 KWH = 3,600 KJ. Assuming 85% of battery energy is converted to mechanical energy in a PHEV that means you need 31030 KJ of energy to get the energy equivalent of a gallon of gasoline. With electricity at about 9.5 cents kwh and you need 8.6 KHW of electricity, that comes to 82 cents for the equivalent of a gallon of gasoline.