America’s electric grid consists of over 450,000 miles of high-voltage transmission lines, supplying millions of customers across the country. Since we use electricity every day, it’s easy to take it for granted, but there are times when people get cut off from this valuable resource.

While blackouts occur all the time and often are easy to manage, there have been cases when localities had to stay without electricity for hours, days, or even months! In this overview, we’ll explore some of the major power outage cases that occurred in the US, take a look at why they happened, and what measures were taken to avoid similar incidents in the future.

5 Worst US Power Outages

Many states in the US have experienced blackouts throughout the years. In this list of major power outages, you’ll learn about the ones with the biggest impact:

1. Northeast Blackout (1965)

When a 230-kilovolt transmission line near Ontario, Canada, tripped on November 9, 1965, it caused several other heavily loaded lines to fail and created what we now know as the Northeast blackout. 

The power outage lasted for nearly 13 hours and left over 30 million people without electricity. The scale of this emergency was truly grand, with 800,000 people trapped in the New York subway, thousands stuck in elevators and trains, and 10,000 National Guardsmen and 5,000 off-duty policemen called into service.

The blackout affected eights states, namely:

• Connecticut
• Massachusetts
• New Hampshire
• New Jersey
• New York
• Rhode Island
• Pennsylvania
• Vermont

This multi-state power outage also left parts of eastern Canada plunged into darkness.

The main cause of this disaster was human error, with a protective relay on a transmission line set incorrectly several days preceding the accident.

To prevent this situation from repeating itself, many organizations took measures. For instance, the Electric Power Research Institute helped create and implement improved metering, monitoring systems, and other equipment, which are still in use today.

2.  New York City Blackout (1977)

This big power outage happened on July 13, 1977. It was caused by a lightning strike on the substation by the Hudson River that tripped two circuit breakers. Shortly, two more lightning strikes followed, and, after an hour, NYC’s largest power generator went down.

The New York power outage was accompanied by riots and looting across the city. The Crown Heights neighborhood had 75 stores within a 5-block stretch looted, while the Bushwick area had to deal with fires caused by arsonists. 

By the time the power was restored 25 hours later, the city had suffered from over 1,000 fires, and 1,600 stores had been ransacked.

3. Northeast Blackout (2003)

The Northeast Blackout of 2003 was much larger than the one that occurred in 1965, affecting 45 million people across 8 states.

The emergency was triggered by a software bug at FirstEnergy Corporation. The power outage started in Ohio, where overloaded transmission lines hit untrimmed trees. The alarm didn’t work, so the maintenance workers weren’t warned of the hazard on time. What started as a rather easily manageable issue became a huge problem for the electric grid.

During the Northeast Blackout, most essential services remained operational in most areas. However, phone services were experiencing an overload in calls, while Detroit lost water pressure and was under a water boiling advisory for even 4 days after power was restored. In Cleveland and New York, many beaches were closed due to sewage water spills into the waterways.

Due to this massive power outage, the national energy policy was adjusted with a focus on infrastructure protection and homeland security.

4. Southwest Blackout (2011)

Known as the worst blackout in California’s history and one of the biggest blackouts in the US, this emergency occurred because of the state’s reliance on power imports from Arizona at the time.

Heatwaves at the end of the summer season that year interfered with CA’s planned outages, delaying the maintenance and leaving the grid vulnerable to human errors. Hence, when a technician turned on major equipment, it caused the power to fail for approximately 12 hours, affecting 2.7 million Americans.

Besides, a plethora of restaurants and grocery stores had to get rid of food due to the absence of refrigeration for an extended period, with the losses summing up to $12 - $18 million. 

Several sewage pumping stations also failed, creating a water hazard in many areas. The Southwest blackout was the turning point after which diesel generators were installed at 5 pumping stations.

5. Hurricane Sandy Power Outages (2012)

When Hurricane Sandy hit the East Coast of the US in October 2012, many people lost their property due to flooding and strong winds. Yet another reason for significant distress was caused by the power outages that affected over 8 million people across 21 states. While in some places the electricity reappeared in a matter of days, other areas had to wait for weeks for the power to be restored.

Most Impactful Power Outages Worldwide

Naturally, wide-scale power outages happen not only on US territory. Here are the largest blackouts the world has witnessed so far:

1. 2012 India blackouts, July 30–31 - 620 million people affected
2. 2001 India blackout, January 2 - 230 million people affected
3. 2021 Pakistan blackout, January 9 - 200 million people affected (90% of the population)
4. 2014 Bangladesh blackout, November 1 - 150 million people affected
5. 2015 Pakistan blackout, January 26 - 140 million people affected

However, the longest power outage occurred in the Philippines in 2013 - it lasted for 6.3 billion customer-hours. This number was achieved by multiplying the number of hours by the population affected.