Dr. Mike Walden, North Carolina Cooperative Extension economist in the College of Agriculture and Life Sciences at N.C. State University, responds:

"Well, the issue here is, of course, that as the use of hybrid cars increases, you are going to have an increased use of electricity. And so you are going to have to ask, Where does that electricity come from? Now, electricity is not - contrary to what some people think - a basic fuel. It is a derived fuel from basic fuels like oil, coal, hydropower, nuclear, solar or wind power. So the more hybrids we have, the more electricity is going to have to be generated from some combination of those basic fuels. And one estimate suggests that if hybrids eventually make up 20 percent of new car sales, we could potentially need about 160 new power plants built somewhere in the country, depending on when people plug in to recharge their hybrid power. The question then becomes, Where will they be built? A lot of people don't like to live near power plants. And perhaps most importantly what kind of fuel they will use?"