These maps show how the renewable resources of wind, geothermal, and solar energy are distributed across the United States, along with the locations of existing and proposed nuclear reactors. To transport electricity from renewable-rich areas to other parts of the country (particularly the East and West Coasts), groups such as the Center for American Progress, a Washington-based think tank, have proposed a new national network of high-capacity transmission lines. While the need for expanded local and regional transmission lines is clear, the argument for an overhauled national network is less so. Building such a system would be expensive, and the money may be more effectively spent in local improvements such as smart meters (see "Intelligent Electricity").