"The U.S. electrical grid is the largest interconnected machine on Earth: 200,000 miles of high-voltage transmission lines and 5.5 million miles of local distribution lines, linking thousands of generating plants to factories, homes and businesses. The National Academy of Engineering ranks it as the greatest engineering achievement of the 20th century.
What it cannot do is support the massive shift to low-carbon power that scientists warn will be needed to avoid catastrophic climate change impacts.
To shrink the electricity sector's carbon footprint, experts say, the nation needs to build thousands of miles of new transmission lines over the next 20 years to connect more renewable resources to electricity demand centers. A 21st-century "smart grid" will also have to balance fluctuating power flows from wind and solar generation, small-scale distributed sources, and plug-in electric vehicles. And it must be interactive so that customers can manage their electricity use.
The transition is already under way, although it means different things for different companies. Firms that operate long-distance transmission lines, such as the Independent System Operators that manage regional grids in New York, New England and the Midwest, are adding sensors, phasors, and other devices invisible to non-engineers, that give them much more precise control over the system."