Everyone knows that gasoline is made from oil, and how much a gallon of the stuff costs at the pump, but most people would be hard pressed to accurately explain what a kilowatt-hour is, let alone what one costs, or how it was made. Thankfully, research suggests that when people plug in their cars, they start to think differently about their energy sources and choices. If you choose to drive on electricity, you’ll be driving free of oil, as less than one percent of our nation’s electricity is derived from petroleum. Driving an electric car on the average U.S. electricity mix also emits only half the amount of global warming pollution as does the average new passenger vehicle. In California, where the grid is cleaner, an electric car emits only a quarter as much. However, many drivers are motivated to go even further and drive emission-free, often on homemade energy.