For your reference, here's my annual energy costs. Sacramento region, PGE. I was on E1 rate until June 2011. Bought the Volt mid-April 2011, used L1 charging until mid-June 2011.
Here's the actual energy usage, by month, for the last year.
Here's a sample of the time of use energy cost for a typical day. The high use in the off-peak not only refects the car charging between 12am and 3:45 am, but also swimming pool circulation starting at 2am.