The 10 Worst Power Outages in U.S. History

The United States has one of the most complex electrical grids in the world — roughly 7,300 power plants, 160,000 miles of high-voltage transmission lines, and millions of miles of local distribution wires. When parts of this system fail, the consequences can be catastrophic: millions of people in the dark, billions of dollars in economic damage, and in the worst cases, loss of life.

Here are the ten worst power outages in American history, ranked by the number of people affected and the severity of the impact.

1. The 2003 Northeast Blackout

On August 14, 2003, a software bug at FirstEnergy’s control center in Ohio failed to raise an alarm when overloaded transmission lines sagged into overgrown trees. Within minutes, a cascading failure knocked out 256 power plants across eight U.S. states and the Canadian province of Ontario. An estimated 55 million people lost power — making it the largest blackout in North American history.

New York City went completely dark. Commuters were trapped in subway tunnels. Water pressure dropped as pumps failed. The economic cost was estimated at $6–$10 billion. The outage lasted up to four days in some areas, though most of New York City had power restored within 29 hours.

“The cascading failure spread across 9,300 square miles in approximately nine seconds — faster than any human operator could have intervened.”
— U.S.–Canada Power System Outage Task Force

2. Winter Storm Uri (2021)

In February 2021, a polar vortex plunged Texas into sub-zero temperatures that the state’s power grid was never designed to handle. Natural gas wells froze. Wind turbines iced over. Coal piles became unusable. Within hours, ERCOT (the state’s grid operator) was forced to implement rolling blackouts that became anything but rolling — millions of Texans went days without electricity in freezing temperatures.

At its peak, 10 million people were without power. The storm caused an estimated 246 deaths (many from hypothermia), $195 billion in property damage, and led to wholesale electricity prices spiking to $9,000/MWh — the market cap. It remains the deadliest power outage in modern U.S. history and triggered sweeping regulatory changes for ERCOT and Texas energy providers.

3. Hurricane Katrina (2005)

When Hurricane Katrina made landfall on August 29, 2005, it destroyed or severely damaged electrical infrastructure across the entire Gulf Coast. In southeastern Louisiana and coastal Mississippi, the grid wasn’t just disrupted — it was physically demolished. Transmission towers were twisted like pretzels, substations were submerged, and entire distribution networks had to be rebuilt from scratch.

Some 2.6 million customers lost power. In the hardest-hit areas of New Orleans, power wasn’t fully restored for over six weeks. The total economic damage from Katrina exceeded $200 billion (2026 dollars), making it the costliest natural disaster in U.S. history.

4. Superstorm Sandy (2012)

Superstorm Sandy struck the densely populated Northeast corridor on October 29, 2012, flooding subway tunnels in Manhattan, destroying beachfront communities in New Jersey, and knocking out power to 8.5 million customers across 21 states. The combination of a hurricane-force storm surge with record-high tides devastated coastal electrical infrastructure.

Lower Manhattan went dark for nearly a week. In the Rockaways and parts of Staten Island, power wasn’t restored for two weeks. The storm caused an estimated $65 billion in damage and directly led to major infrastructure hardening programs across the Northeast.

5. Hurricane Irma (2017)

Hurricane Irma barreled through Florida on September 10, 2017, as one of the most powerful Atlantic hurricanes ever recorded. The storm knocked out power to 6.7 million customers — roughly 64% of all Florida electricity accounts. It was the largest weather-related outage in the history of a single state at that time.

Florida Power & Light, the state’s largest utility, deployed 20,000 restoration workers from across the country. Full power restoration took 12 days. The economic impact was estimated at $50 billion.

6. Hurricane Maria (2017)

Hurricane Maria devastated Puerto Rico on September 20, 2017, destroying virtually the entire electrical grid on the island. All 3.4 million residents lost power. What made this outage uniquely catastrophic was its duration: some rural areas didn’t have electricity restored for nearly 11 months, making it the longest blackout in U.S. history.

The storm killed an estimated 2,975 people (many from lack of medical care during the extended outage) and caused $90 billion in damage. It exposed the extreme vulnerability of island grids and became a catalyst for Puerto Rico’s ongoing push toward solar microgrids and grid modernization.

7. The 1977 New York City Blackout

On the night of July 13, 1977, lightning struck transmission lines north of New York City, triggering a cascade of equipment failures that plunged the entire city into darkness. Unlike the orderly 2003 blackout response, the 1977 event coincided with a heat wave, high unemployment, and social unrest. The result was widespread looting and arson — over 1,600 stores were damaged, more than 1,000 fires were set, and 3,776 people were arrested in a single night.

Power was restored within 25 hours, but the event permanently changed how utilities approached grid resilience and emergency response in urban areas.

8. The 2012 Derecho

On June 29, 2012, a massive derecho — a fast-moving line of severe thunderstorms with sustained, hurricane-force winds — swept from Iowa to the Mid-Atlantic coast in roughly 12 hours. The storm traveled 700 miles with wind gusts exceeding 90 mph, snapping power poles and toppling trees onto distribution lines across a dozen states.

An estimated 4.2 million customers lost power. Restoration took up to 10 days in some areas, complicated by extreme heat (temperatures exceeded 100°F) that followed the storm. Twenty-two people were killed.

9. The 2008 Northeast Ice Storm

In December 2008, a massive ice storm coated New England and upstate New York in up to an inch of ice, snapping tree limbs and power lines across the region. Over 2.1 million customers lost power, many for more than a week. In rural New Hampshire, some residents went without electricity for 14 days in freezing conditions.

The storm demonstrated the particular vulnerability of overhead distribution lines to ice loading — a weight of ice on wires that ground-level observers often can’t see until lines snap.

10. Hurricane Harvey (2017)

Hurricane Harvey made landfall near Rockport, Texas, on August 25, 2017, then stalled over the Houston metropolitan area for four days, dumping over 60 inches of rain in some locations. While the wind damage was significant, it was the unprecedented flooding that caused the most devastating electrical impact. Substations were submerged, underground infrastructure was waterlogged, and over 300,000 customers lost power.

The storm caused $125 billion in total damage, making it one of the costliest natural disasters in U.S. history. The electrical grid challenges were compounded by the fact that many homes couldn’t safely receive power restoration until floodwaters receded and electrical systems were inspected.

Lessons for the Future

Several common themes emerge from the worst outages in American history:

• Cascading failures are the real threat. Most major outages start with a localized failure that spirals because protective systems fail to isolate the problem. The 2003 blackout spread across 9,300 square miles in seconds.
• Extreme weather is the #1 cause. Eight of the ten worst outages were weather-driven. As climate patterns intensify, the grid faces increasing stress from events it was never engineered to withstand.
• Duration matters more than darkness. The number of people affected grabs headlines, but it’s the duration of the outage that determines the humanitarian impact. Puerto Rico’s 11-month blackout caused far more suffering than the 29-hour 2003 Northeast blackout.
• Grid modernization is essential. Every major outage has accelerated investment in smart grid technology, vegetation management, grid hardening, and distributed energy resources. The shift toward microgrids, battery storage, and rooftop solar is partly a direct response to these events.

If you live in a deregulated state like Texas, Pennsylvania, or Ohio, understanding your electricity options — including backup power and provider reliability — is more important than ever. Compare electricity rates in your area to find the plan that best fits your needs.