July's broiling heat and wind-driven storms are big risks for power outages from the dry desert southwest to the swampy East Coast. Outages are usually local, with downed lines leaving us in the dark for a few hours or perhaps a day. But what are the chances of something worse happening? What if the entire U.S. power grid went kaput?
Many experts say that's an unlikely event. The nation's power grid is a complex, yet technologically advanced, system with plenty of backup. But scenarios do exist that could lead to such a massive failure: a solar flare, a cyberattack, or even just a series of unfortunate events -- also known as a cascading failure.
"It is conceivable," said Ian Dobson, professor of engineering at Iowa State University who focuses his research in preparing for just that possibility. "If there is a series of failures, then the grid doesn't have sufficient redundancy to transmit electricity and the load is shed, that is a blackout and the lights go out."
If it's a just a matter of rebooting the system, that can be done in a couple of hours, explained Dobson. But if there's physical damage to high-voltage transmission lines, substations or other infrastructure, it could take weeks or months to replace and repair transformers or other equipment.
Modern society without electricity would obviously be a tough place to live. Electricity keeps clean water running, communications operating, food cold, hospitals open and our homes and streets safe. Most backup systems, like diesel generators, are only designed to run for a few days.
Government and industry officials appear to be most worried about temporary, regional blackouts, the kind that happened along the East Coast in 2003 when a software malfunction tripped the power for 45 million U.S. residents in six states, and another 10 million Canadians.
Human error -- a decision by a technician to cut a high-voltage line between two substations -- led to a 12-hour blackout for 6 million people in California, Arizona and Northern Mexico. Sewage pumps failed, spilling contaminated water onto beaches, and food spoiled in thousands of groceries.