The answer to that truly depends on where you live, and perhaps which billing option you select (if available). According to the U.S. Energy Information Administration, as of May 2010 the highest average electricity rate was in Hawaii ($0.2825 per kilowatt hour) while the lowest rate was in Idaho ($0.0803 per kilowatt hour). The average rate in the US is $0.1196 per kilowatt hour. This though, does not even come close to telling the story.
We will use California as an example, as California currently has the most LEAF reservationists. According to the above chart, California has an average rate of $0.1543 per kilowatt hour. But San Diego Gas & Electric has created an Electric Vehicle (EV) rate structure, specifically for those in The EV Project.
Essentially, the rate structure is created to reward off-peak usage. There will be three tiered rate structures. It is unknown how one determines which structure will apply. One group offers an off-peak rate of $0.14-$0.17 per kilowatt hour for off-peak usage and $0.27 during peak summer hours. A second group varies from $0.076 for off-peak to $0.30 for peak usage. A third group would have the lowest off-peak rate of $0.067 for off-peak usage, but $0.38 for peak summer usage. Winter usage rates may differ.
The first group would provide charging costs of $3.36 to $4.08 off-peak but $6.48 on-peak to fully charge the 24 kilowatt hour LEAF battery from “empty”.
The second group would see charging costs of $1.82 off-peak and $7.20 on-peak.
The third group would see charging costs of $1.61 for off-peak and $9.12 for on-peak usage.
It is clear from the design of the program, that SDG&E is encouraging off-peak charging while discouraging on-peak charging. As this is written, it is unclear if the remainder of the home will remain on standard “Residential Service” rates.
What can be seen from this illustration is that it is important to check with your utility provider to see what, if any, plan they may offer to EV owners. If you “opted in” to the EV Project, that free Electrical Vehicle Supply Equipment (EVSE) unit comes with strings attached. We know study participants are required to provide data to the study. If “EV Project rate structures” exist, we will also likely be subject to their terms. This statement is directly from The EV Project overview page:
The EV Project will collect and analyze data to characterize vehicle use in diverse topographic and climatic conditions, evaluate the effectiveness of charge infrastructure, and conduct trials of various revenue systems for commercial and public charge infrastructure.
Two things to take away from this: be sure to check the rate structures offered by your utility company, and “free” (as in free EVSE) does have some conditions attached to it.