Blackout and brownout are terms associated with electricity. More or less, they are similar in a way but with several significant differences.

While a brownout is a temporary reduction of power, a blackout is the complete loss of power and is often more serious when we speak about brownout vs blackout.

Blackout and brownout are common occurrences, and they are inevitable. As our demand for electricity increases, the same applies to the probability that brownout or blackout will occur at some point to our power systems. Despite efforts to enhance the total system capacity of the power grid system and improve it for optimal performance, it’s still not enough to match peak power demands.

This article on brownout vs. blackout will discuss the meaning of brownout, blackout, their causes, and key differences.

Meaning of Brownout

A brownout is an accidental or deliberate drop in the voltage provided by the electrical grid. In case of an intentional brownout, it’s usually a temporary reduction of the electric voltage supplied by the local utility company as an emergency measure. Brownout is a concept coined from the dimness of incandescent light bulbs when there’s a power reduction.

What Causes Brownouts?

This reduction in system voltage can either be because of a disturbance in the electric grid or imposition by the utility company to lessen the load or avoid a power outage.

Brownouts can also occur because of severe weather conditions or high electricity demand. However, the meaning of a brownout is not consistent across countries. A brownout is not an intentional or unintentional drop in voltage in specific countries but a deliberate or accidental power outage. In essence, blackout and brownout are interchangeable terms in these countries.

Effects of Brownout

Various electrical appliances react differently to a temporary drop in voltage from the electrical power supply system. As a result, some electrical equipment may not be affected, while some can be affected severely. The heat emission of every resistive device, like a water heater, matches the energy consumption, which matches the voltage it receives.

If this resistance is consistent, energy usage will be proportionate to the square of the applied voltage. This will mean that a substantial reduction of heat emission will occur if there is a slightly small reduction in voltage. Unfortunately, this also means your incandescent light bulb will be gone from bright to dim because of lesser heat in the filament and lesser conversion of this heat to light. There will be no damage, but it will significantly reduce efficiency.

Electric motors that convert alternating current to direct current will move at lesser speed or torque. For some specific motor designs, this may not cause any harm. However, the motor may consume more current because of the lower counter electromotive force generated at a reduced armature speed. This can lead to the electrical system overheating and burning out if it lacks an efficient cooling capacity.

Induction motors will suck in more electric current to make up for the voltage drop, but this may make it overheat and burn out. If electric motors make up a significant part of the grid’s load, a voltage drop may not lead to load reduction, which can damage appliances receiving electric power. When direct current is not regulated, it will generate a lesser output voltage for electronic circuits. This voltage generated will lessen in proportion to the load current.

For sensitive electronics such as a cathode-ray tube television, the lesser output voltage will cause the television screen to display dimmer and smaller.

Meaning of Blackout

A blackout can also be called a power cut, power failure, or power loss. It’s the loss or complete interruption of electric power to a consumer. A lot of things can trigger blackouts. Certain factors such as the electrical network configuration or the nature of the blackout affect the duration of a blackout. It can range from a few minutes to a couple of weeks.

What Causes Blackouts?

Notable causes of blackouts include fault at power plants, damaged electric supply wires, substations, or alternate components of the grid, circuit breaker operation, short circuits, or cascading failure. Specific facilities, especially those directly associated with environmental safety such as sewage treatment plants and mines or public health sites such as hospitals, typically have standby generators as a backup source of electric power.

The moment a power outage occurs, they automatically power on. Even telecommunication systems are required to have a backup power source. This can be crucial during lengthy periods of power failure.

Rolling Blackouts

Rolling blackout is the type of blackout that is triggered when power demand surpasses its supply, and some consumers receive electric power supply to the detriment of others. This commonly happens in developing countries, and it may occur unexpectedly or scheduled to occur at a specific time. In the case of the latter, this can induce power outage preparedness.

There are also cases of rolling blackouts happening in advanced countries. A good instance of this was the electricity crisis in California between 2000-2001 when deregulation policies disrupted the wholesale electricity market.

Blackout as a Public Safety Measure

Blackout is also used for public safety to prevent a gas leak from igniting. The Merrimack Valley gas explosions are a notable instance. As a result, the electricity being supplied to several towns was cut off. It’s also used to avoid the occurrence of wildfires in areas where poorly maintained power lines are situated. An excellent example of this is the California blackout in 2019.

Key Differences Between Brownout vs Blackout


Brownouts last for a very short time, while blackouts last for longer. In some cases, blackouts can take weeks, as earlier mentioned.


Brownouts are caused by disturbances (such as extreme weather conditions) in the power grid or deliberately carried out by utility companies to prevent a blackout. On the other hand, blackouts are triggered by faulty transformers, damaged fuses or circuits, or badly maintained power lines.

Effect on Appliances

Brownouts may or may not affect appliances (depending on the appliance), while blackouts don’t affect appliances.

How They Work

Voltage reduces and then returns to optimal level within 1 minute. On the other hand, Blackout is total disruption and cessation of power supply.

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