distribution circuits may need upgrading if they are to serve clusters of PHEVs. Encouraging PHEV owners to charge their vehicles during off-peak hours will require both rate schedules that reward time-appropriate charging and equipment that can monitor—or even control—time of use.
A portfolio approach to research, development, demonstration, and, perhaps, market transition support is essential. It is not clear what technology or combination of technologies—batteries, hydrogen, or biofuels—will be most effective in reducing the nation's oil dependency to levels that may be necessary in the long run. It is clear, however, that a portfolio approach will enable the greatest reduction in oil use. Increasing the efficiency of conventional vehicles (including HEVs) beyond the current regulatory framework could reduce gasoline consumption by about 40 percent in 2050, compared to the Reference Case. Adding biofuels would reduce it another 20 percent. If PHEV-10s are also included at the Maximum Practical rate, gasoline consumption would be reduced an additional 7 percent, while PHEV-40s could reduce consumption by 23 percent. Employing HFCVs instead of PHEVs could eliminate gasoline use by the fleet.