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What is a brownout vs blackout?

What is a brownout vs blackout?

Power outages can be disruptive and dangerous, especially when they occur unexpectedly. There are two main types of power outages: brownouts and blackouts. Both involve disruptions in electrical service, but there are important differences between the two. Understanding what causes brownouts and blackouts, and learning how to prepare for them, can help minimize the impact when they occur.

What is a Brownout?

A brownout is a drop in voltage in an electrical power supply system. It typically lasts for minutes to hours. The reduction in voltage causes the electricity supply to become unstable, which can cause disruptions and damage to equipment.

Some key characteristics of brownouts:

– Voltage drops significantly, but some electricity flow is still present.

– Power levels can fluctuate, going up and down during a brownout.

– Lights may dim and electronic devices may work poorly or slowly.

– Brownouts often occur when power demand exceeds supply, such as on hot summer days when air conditioner use surges.

– Brownouts do not cause power to go completely out, but can disrupt and damage sensitive electronics.

What Causes Brownouts?

Some of the most common causes of brownouts include:

– Increased electrical demand – If demand surges due to high usage of heating/cooling systems, appliances, etc., it can overload the system and cause voltage drops.

– Problems with power generation – Issues with power plants and other infrastructure can cause supply disruptions leading to brownouts.

– Failures along transmission lines – Damage or disruptions along transmission lines from power plants can reduce voltage.

– Weather issues – Heat waves, storms, and other extreme weather can damage power equipment and cause brownouts.

– Accidents – Accidental damage to power poles, transformers, and other grid components can necessitate voltage reductions.

What Happens During a Brownout?

When a brownout occurs, the reduced voltage can cause multiple effects:

– Lights dim – Incandescent bulbs and CFLs will get noticeably dimmer. LED lights may be less affected.

– Voltage-sensitive electronics may fail or work intermittently. These include medical devices, motors, and digital electronics.

– Devices may run slower. Electric motors in appliances will operate under lower power.

– Damage to electronics – Voltage fluctuations during brownouts can damage sensitive electronics and shorten their lifespan. Surge protectors help.

– Lower energy efficiency – Devices like air conditioners run less efficiently with reduced voltage input.

– Safety systems may activate – Safety mechanisms may shut off devices if voltage drops too low.

How to Prepare for a Brownout

To limit the impacts of a brownout, you can take these steps to prepare:

– Get surge protectors – They will help safeguard electronics from voltage spikes and dips.

– Unplug unused electronics – This prevents accidental damage if there are power fluctuations.

– Have emergency lighting ready such as flashlights and battery-powered lanterns.

– Keep batteries charged for backup power needs. External battery packs can charge phones.

– If you rely on medical devices, discuss a backup plan with your doctor.

– If on a municipal power grid, contact your utility company to report any service issues.

– For a home backup generator, ensure it is tested and fueled. Install a transfer switch.

– Know how to safely reset tripped breakers and electrical equipment.

What is a Blackout?

A blackout is a total loss of electrical power. It is also referred to as a power outage or outage for short. Unlike a brownout, a blackout causes all electric lights and appliances to stop working.

Some key characteristics of blackouts:

– All power is lost, plunging affected areas into darkness.

– Loss of electricity can last minutes, hours, or even days depending on cause and infrastructure.

– Widespread grid failures lead to large multi-state blackouts.

– Even small localized blackouts can impact thousands of electricity customers.

– Lack of power poses safety risks and enables crime such as looting.

What Causes Blackouts?

Some typical causes of blackouts include:

Cause Description
Grid/power plant failures Mechanical or operational failures during power generation and distribution.
Overloaded grids Electricity demand exceeds capacity at times of peak usage.
Power lines damaged Storms, accidents, or other issues that damage infrastructure.
Equipment failure Breaker, transformer, or insulation failures that interrupt service.
Short circuits Typically when power lines touch each other or the ground.
Operator error Human mistakes made by utility staff.

Effects and Risks of a Blackout

When blackouts strike, the loss of power causes wide-ranging effects:

– Darkness – Loss of lighting except for battery or generator backups. Increased risk of accidents and crime.

– Communication blackouts – No internet, TV/radio, or phone service. Hampers coordination of recovery efforts.

– Transportation disruptions – Traffic signals out, rail lines affected. Mass transit shuts down. Air travel delays.

– Food spoilage and water contamination – Refrigeration and pumping stations lose power. Health hazards arise.

– Loss of heating/AC – Extreme health risks for vulnerable populations if power loss is prolonged.

– Economic losses – Businesses forced to close. Production halted. Transactions and commerce disrupted.

– Safety and security issues – Alarms, security cameras/systems, street lights disabled. Fire and crime risks increase.

How to Prepare for a Blackout

These tips will help you prepare for power outages:

– Have flashlights and batteries. Candles are fire hazards.

– Charge external battery packs to charge phones when power is out.

– Unplug unused appliances and electronics to avoid damage during an outage.

– Have a battery-powered or hand-crank radio for news updates.

– Stock up on non-perishable foods and bottled water.

– Know how to manually open electric garage doors, security gates, etc.

– Install a home generator with fuel supply. Ensure proper generator safety.

– Have a cooler and ice packs to keep food cold if the outage is prolonged.

– Keep cash on hand since ATMs won’t work during a blackout.

– Use surge protectors to protect electronics when power is restored.

– If on life support, discuss backups with your doctor or care provider.

Differences Between Brownouts and Blackouts

While both brownouts and blackouts involve disruption of electrical service, there are key differences:

Brownout Blackout
Voltage level Decreased Zero
Lights Dim Out
Electronics May work poorly Turn off
Outage duration Minutes to hours Hours to days
Causes Overloaded grids, issues with power distribution Equipment failure, accidents, natural disasters
Geography Localized Can be widespread


Brownouts and blackouts can both be significant disruptions, but blackouts tend to have wider-ranging effects due to the total loss of power. Being prepared with backup lighting, communications, food and water, and alternate power sources can help minimize the impacts to daily life and work. Following local utility companies on social media can provide advance warnings if a brownout or blackout is planned for repairs. Taking preventative measures to safeguard equipment against voltage surges can also help minimize damage. Though disruptive, being informed about the distinctions between brownouts and blackouts helps promote readiness and resiliency.