Abstract: Electric-drive vehicles, whether fueled by batteries or by liquid or gaseous fuels generating electricity on-board, will have value to electric utilities as power resources. The power capacity of the current internal combustion passenger vehicle fleet is enormous and under-utilized. In the United States, for example, the vehicle fleet has over 10 times the mechanical power of all current U.S. electrical generating plants and is idle over 95% of the day. Electric utilities could use battery vehicles as storage, or fuel cell and hybrid vehicles as generation. This paper analyzes vehicle battery storage in greatest detail, comparing three electric vehicle configurations over a range of driving requirements and electric utility demand conditions. Even when making unfavorable assumptions about the cost and lifetime of batteries, over a wide range of conditions the value to the utility of tapping vehicle electrical storage exceeds the cost of the two-way hook-up and reduced vehicle battery life. For example, even a currently-available electric vehicle, in a utility with medium value of peak power, could provide power at a net present cost to the vehicle owner of $955 and net present value to the utility of $2370. As an incentive to the vehicle owner, the utility might offer a vehicle purchase subsidy, lower electric rates, or purchase and maintenance of successive vehicle batteries. For a utility tapping vehicle power, the increased storage would provide system benefits such as reliability and lower costs, and would later facilitate large-scale integration of intermittent-renewable energy resources.