Last Updated on February 1, 2025
Electrical disturbances are on the rise. In 2020 1.33 billion hours of power outages occurred in the United States. A 73% increase from 2019. These electrical disturbances take two forms, blackouts and brownouts. But what’s the difference?
A Blackout is a term given to the complete disruption of an electrical system. In contrast, a brownout is only a temporary voltage drop. Brownouts are typically premeditated, whereas blackouts come at a moment’s notice and without warning. Both are hard to prevent and are affected by environmental factors and the supply of energy.

What Is a Blackout?
A blackout is a complete disruption in the flow of power within any given service area. Blackouts come without warning and can last an indeterminate amount of time.
The most common cause of a Blackout is extreme weather, damaging power lines, and other electrical equipment. As a result, blackouts are hard to predict.
Rolling Blackouts
While most blackouts are unintentional rolling blackouts are the rare exception.
Rolling blackouts are systematic temporary power outages used to restore balance to the supply and demand of the electrical system.
Typically rolling blackouts are authorized by a government agency or electrical supplier. They are a last resort in a series of emergency procedures after a shortage in the power supply.
Rolling blackouts occur on a much smaller scale than blackouts. They are induced with the desire to prevent a prolonged, more widespread blackout.
While rolling blackouts are deliberately induced, they can last for an indeterminate amount of time, much like regular blackouts.
What is a Brownout?
A brownout refers to the temporary drop in voltage in an electrical power supply system. Brownouts can last between a few minutes to a couple of hours. Typically a utility will decrease its voltage by 10-25%.
The name brownout derives from the dimmer light emitted by lighting as a result of the diminished voltage.
Appliances and electrical equipment respond to brownouts in different ways. The reduced voltage can severely hinder some, while others show no signs of being affected.
The power reduction has little effect on heating and lighting systems. Such appliances can operate at suboptimal voltage levels effectively.
However, appliances that require precise voltages cannot function under these conditions. Long-term brownouts can cause unnecessary wear on sensitive electronic devices.
Intentional Brownouts
Unlike blackouts, brownouts can be intentionally imposed. Electrical providers can do a deliberate brownout as an emergency measure to prevent the system from stopping completely (causing a blackout).
The theory behind this method is to reduce the burden on the electrical system and keep some degree of power rather than losing it altogether.
What is the Difference Between a Blackout and a Brownout?
Blackouts and brownouts are both disturbances in the electrical supply, so what makes them different? Here is a summary of the key differences.
Blackout | Brownout |
---|---|
Unintentional | Intentional |
Last for an undetermined amount of time | Last for a few minutes to a couple of hours |
Complete disruption to the power supply | Temporary reduction in power supply |
Few methods of prevention | Few methods of prevention |
What Causes a Blackout?
There are an array of different factors that can lead to a blackout:
- Storms or extreme weather: heavy rain, snow, and wind can all contribute to the destruction of electrical equipment and power lines resulting in an outage.
- Earthquakes: earthquakes can be one of the cause s
- Trees: Hind weeds can cause trees to fall and damage power lines.
- Animals: Small animals such as squirrels, snakes, and birds can all cause damage to power lines
- High power demand: Heatwaves and freezing temperatures can cause people to rely more heavily on electrical appliances. This increased demand across the board creates a greater electricity demand and can cause outages.
- Vehicles: A vehicle crashing into a utility pole could cause a temporary power outage.
- Excavation digging:
How to Prevent Blackouts?

With the causes of blackouts being so unpredictable and usually dictated by nature, little can be done to prevent blackouts from occurring. Reducing energy consumption and turning off appliances is one effective way of decreasing the risk of a blackout.
However, the high energy demands that usually bring about blackouts come at times of extreme heat or cold when such energy demands are vital for survival.
See Also: Best Generators from Generac
What to do in the event of a Blackout?
In the event of a blackout, turn off all electrical appliances. Avoid the temptation of turning on any generators or grills indoors and away from windows. These items can release carbon monoxide and can potentially be deadly.
To reduce the impact of a blackout, ensure you have the following items in your home.
- A good supply of nonperishable food and bottled water
- Candles and torches or other non electrical dependant lighting
- First aid kit
What Causes a Brownout?
There are an array of different factors that can lead to a brownout:
- High power demand: an increased need for power may cause voltage fluctuations as the supplier struggles to meet demands.
- Severe weather: extreme weather can damage power lines, and a need for energy suppliers to redirect electricity to where it is needed most.
How to Prevent Brownouts?
There are few ways to prevent a brownout. If the power shortage results from a disturbance in your electrical grid, there is little you can do.
However, if the brownout is a result of a shortage or fault in your homes own power supply, several measures can be taken:
Limit the Use of Large Electrical Appliances
Appliances such as washing machines and air conditioning can consume a lot of electricity. Make sure that such appliances are used efficiently to prevent using too much power.
Use Appliances Only When Needed
Everyone likes to have all their appliances on all of the time. What people do not understand is the amount of energy that is required. Help cut down the risk of a power shortage by turning on your appliances as and when they are needed.
Check Electrical Circuits Regularly
Inspect your circuit breakers for any signs of corrosion or bad terminals. If so, repair or replace them immediately.
What to do in the event of a Brownout?
In the event of a brownout, the first thing to do is not to panic. Next, get in contact with your electrical provider to see if the reduction in power is caused by a disturbance in the electrical grid.
If this is not the case, that means the brownout is a consequence of a disturbance in the home. Such an event can be brought about by the overuse of power or a fault in your home’s electrical supply. If so, contact an electrician immediately and arrange a meeting so they can assess the problem.
In both instances, to help prevent damaging any electrical equipment, turn off all electrical appliances. A sudden surge in voltage can cause necessary wear and tear on appliances. Once the power has returned to normal, turn the electrical appliances back on.
See also: Can a generator run in the rain?
Final Thoughts
There it is, a complete and comprehensive guide to the differences between blackouts and brownouts. At first sight, they may seem very similar. Still, on closer inspection, it is clear that crucial distinguishing factors separate the two.
Blackouts are highly unpredictable and definitive cuts in power. In comparison, brownouts are organized and are a temporary reduction in voltage.
Either way, you know what to do in either instance and effectively prepare for each event.
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