A large amount of surplus electricity-generating capacity is generally available during off-peak hours. To moderate costly fluctuations in power consumption and production throughout the day, utilities could provide a price incentive to encourage electric vehicle owners to charge during off-peak periods. Doing so would lower the cost of integrating the vehicles with the grid and could even lower prices if the average cost of delivering electricity is lowered for all ratepayers.
One way to encourage off-peak charging is through time-differentiated, or time-of-use (TOU), electricity rates that offer cheaper electricity overnight when demand is low. Many electric utilities offer TOU rates to manage existing grid assets more efficiently.
The PEV Dialogue Group recommends  electric utilities offer attractive electricity rates for electric vehicles and encourage off-peak charging in order to accelerate electric vehicle adoption and lower vehicle-grid integration costs.
This map displays states with electric utilities that have adopted TOU rates specifically targeted at electric vehicles. Much of the data comes from the Department of Energy’s Alternative Fuel Data Center .
For information about TOU and other electricity rates for most electric utilities, visit the OpenEI website , a joint initiative between the U.S. Department of Energy, the National Renewable Energy Laboratory, and many others.
Last updated: February 11, 2014