America's state governments are at the forefront of efforts to expand the nation's supply of renewable energy. Renewable energy standards (RES) comprise the cornerstone of these initiatives. RES is by far the most widely used mechanism by states to expand renewable energy production and consumption. Fully 29 states have adopted some form of a mandatory RES. RES is also in place in the District of Columbia. And Vermont has a goal that so far has been voluntary, but which may become mandatory by 2013.