Brownout vs. Blackout: What’s The Difference and Causes of Power Disruptions

Written by Kyle Glatz
Updated: July 21, 2023
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Electrical power outages can be both frightening and dangerous. People rely on electricity to power emergency devices, stay cool, keep in contact, and more. The power can go out for many reasons, and two of the over-arching events that cause outages are brownouts and blackouts. Take a look at our comparison between a brownout vs. a blackout and find out the difference between the two and which one is worse.  

What’s the Difference Between a Brownout vs. Blackout?

Blackout in the Ukrainian capital Kyiv. Capital streets without street lighting. Only the lights of passing cars are visible.

Blackouts can endanger people by affecting visibility or removing access to lifesaving machines.

©Drop of Light/

DefinitionA partial drop in voltage, often purposely controlled by utility companies to manage increased demand for power.The complete loss of electrical power in an area.
Causes– The utility company lowers the voltage in the system by 10% to 25% to prevent a complete power failure or blackout.
– Part of the utility company’s infrastructure is damaged but still working at a lower capacity.
-Structural damage to electrical generators prevents power generation.
– Damage to the wires, transformers, electrical poles, or other electrical system infrastructure prevent power from traveling to an area.  
– High power demand overwhelms the system such as during a failed brownout.
Differences– Some electricity is still available for homes to use.
– The utility companies may be able to impact the length of the voltage drop.
– No electricity is available for use until the problems are corrected.
– Utility companies must determine the cause and fix structures when it is safe to do so.

Although both events feature power outages, the primary difference between a brownout vs. a blackout is that a brownout is a partial drop in voltage levels while a blackout is a total loss of power.

Both of these types of power outages can cause widespread problems. Total blackouts can lead to deaths in care facilities and personal residences when they lack a proper backup method. Moreover, a blackout resulting from a natural disaster, like a hurricane, can last for days or weeks depending on many factors.

To understand the brownout vs. blackout differences, it is easiest to look at three facets: their definition, causes, and differences. From there, we can understand which of the two problems is considered worse.  

Defining Brownout and Blackout

The definition of a brownout is a partial drop in voltage triggered by a utility company in response to a demand for power that exceeds the available electricity from a power station. These temporary drops in power can last from seconds to hours depending on many factors.

The average brownout reduces the available voltage by anywhere between 10 and 25 %. A noticeable result of this occurrence is lights going dim rather than going out. Lights dimming is the origin of the brownout term. Although some appliances and household items can operate during a brownout, they can also malfunction in some cases.

Meanwhile, a blackout is the total loss of power in an area. Numerous causes of these events exist. For example, lightning damage to a New York-based power station in 1977 caused a major blackout in New York City. While most people simply stayed home and tried to stay cool during the summer day, others took to the street and rioted.  

Utility companies are not in control during a blackout. Furthermore, brownouts can turn into blackouts if the power company cannot reconcile the demand for electricity with its ability to provide it.

Causes of Both Types of Power Outage

Blizzard in Chicago

Severe weather often knocks out power.

©Jake Hukee/

Brownouts have two major causes. A power company can create them by deliberately lowering the available voltage in their system in response to excess demand at the structure. They can also happen if a portion of a utility company’s infrastructure is damaged but still operable.

Meanwhile, blackouts have many different causes. They include:

  • Damage to a power plant that prevents power generation entirely.
  • Damage to any of the electrical infrastructure that carries power.
  • High power demands completely overwhelm the grid, including failed brownout maneuvers by a power company.

More specific causes of blackouts exist, but these are some of the major causes of such events. Power companies constantly work to keep power systems online. However, tornadoes, floods, and extended heat waves can result in both types of outages.

Differences Between a Brownout and a Blackout

A nuclear power plant in the distance, with steam billowing from its cooling towers.

Sometimes, the energy demand in an area gets too high, prompting a brownout.


Knowing what causes these outages, it’s time to look at some of the chief differences between them. The biggest difference between the two is that some power is still available to use during a brownout. Lights may flicker and heavy-duty appliances like air conditioners may not operate well. Yet, a home will have some power during these events. Meanwhile, there is no power available during a blackout.

Another difference is that blackouts last longer than brownouts in most cases. Purposeful brownouts give some control to the power company in cases where they purposely lower the available voltage on the system. The temporary drop could last just a few minutes.

That is not always the case, though. Sometimes, brownouts are not deliberate. Neither are blackouts. During a blackout event, utility companies must take time to figure out the root cause of the power outage and fix it. If it’s a simple transformer issue, the blackout can be resolved in a neighborhood in minutes. If a tornado destroyed a local substation, then the blackout could last for days or weeks.  

Which Type of Power Outage Is Worse?

Damaged Electrical Power

Having no power is usually worse than having limited power.


Blackouts are worse than brownouts since there is a total loss of power. The former often results from extreme weather. So, if a bad thunderstorm strikes during a heatwave and knocks out the power, then people will have no way to keep cool. Individuals with health problems could even pass away. Also, blackouts tend to last longer, and a longer period without power can usually be considered worse than a momentary power lapse.

Homes and businesses retain some power during a brownout. While that may seem like a mere inconvenience, it can be worse. A prolonged brownout can damage digital appliances. So, people are forced to not use some appliances during a long brownout to prevent them from being irreparably damaged. Depending on one’s perspective, one type of power outage can be worse than the other. Yet, most people would probably have some power than none at all, especially during a crisis.

Many differences exist between a brownout vs. blackout including their causes and the degree to which an area loses power. Although brownouts may be frustrating, blackouts have directly contributed to human deaths in the past. Large-scale power outages are a significant threat to any nation, so ongoing power grid development and maintenance are needed to keep the availability of electricity.

The photo featured at the top of this post is © pamela ranya/

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About the Author

Kyle Glatz is a writer at A-Z-Animals where his primary focus is on geography and mammals. Kyle has been writing for researching and writing about animals and numerous other topics for 10 years, and he holds a Bachelor's Degree in English and Education from Rowan University. A resident of New Jersey, Kyle enjoys reading, writing, and playing video games.

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