How to Make Money From a Car Battery

A March 28 letter from Joanne M. Ivancic, executive director of Advanced Biofuels USA, questioned how people who own electric cars or plug-in hybrids could receive a benefit from utilities for storing energy in their car batteries. "I can't imagine that the company would pay me more than it charges for the stuff," Ms. Ivancic wrote.

However, this would be precisely the case, and it is based on the simple concept of peak (day) and off-peak (night) electricity rates. Charging the battery at night, when rates are lower, and feeding back to the electricity grid during the day would help utility companies by leveling demand. This type of rate structure is common in the power industry, and with the advent of a "smart grid" (an electricity distribution system based on more-advanced metering and communications technologies), residential customers would be able to benefit through significant efficiency increases.

Let's use Ms. Ivancic's own example (let's say 10 units at 10 cents per unit for $1), but consider connecting to the smart grid when at work to supply two units back to the utility. This would be of value to the utility (let's say at 15 cents per unit), since it would not need to increase power generation as much during the day to meet the increased electricity demand. In this example, charging at lower off-peak rates would reduce the daily cost of the work commute by 10 cents.

JOE CRESKO

Arlington

The writer is serving as an AAAS Science Policy Fellow in the Energy Department's Office of Energy Efficiency and Renewable Energy.