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What is a brownout?

Brownouts: What are They? Are They Bad for Computers?

Have you ever noticed your lights dimming or flickering? This is usually caused by a brownout.

However, most homeowners don’t understand brownouts and how harmful they can be.

So we’re answering a list of the most commonly asked questions about this electrical phenomenon.

What is a brownout?

Brownout Lamp Dim

Sometimes called a voltage sag, dip, a brownout is a drop in voltage to your home / business electrical system. Unlike blackouts, you still have power, just less of it. Think of a brownout as the opposite of a power surge. Brownouts typically last from a few minutes to a few hours. They get their name from the color they turn your lights (a dimmed brown instead of brilliant light).

What causes brownouts?

There are 2 main sources of brownouts: external (outside your home / business) and internal (inside your home / business).

External causes of brownouts include:
  • Power grid problems (too much demand and not enough electricity)

  • Power failure at power plants

  • Intentional “throttling” of electricity during peak demand

Internal causes of brownouts include:
  • Too many electrical appliances on a single circuit

  • Inadequate wiring for a large appliance (like an air conditioner, freezer or refrigerator)

  • Bad wiring in the home

To tell if the problem lies in your home or is more widespread, when you experience a brownout, see if your neighbors are also having problems. If not, the problem lies in your demise and you may need to hire an electrician to find the cause.

Are brownouts bad for my computers (and other electronic appliances)?


Don’t take brownouts lightly. The irregular power supply during the brownout can ruin your computer and other electronic devices.

Electronics are created to operate at specific voltages, so any fluctuations in power (both up and down) can damage them.

Also, when your power eventually comes back, the voltages wildly bounce around for a moment (power surges). Those fluctuations can also harm your electronic devices.

How you can protect your electronic devices and appliances

Take these precautions:

  • Unplug computers, TVs, printers, routers, major appliances and cellphones if you’re home during the brownout although impractical in business premises

  • Install surge protected power distribution units power. Again, these won’t protect your devices during a brownout, but can help against the surges that result afterward. But make sure you don't contraveine BS6396:2008

  • six individually fused sockets rated at 3.15 Amps each, or

  • four individually fused sockets rated at 5 Amps each

  • Install a surge protection system. While this won’t help you during a brownout, it can protect against the surges that usually happen after a brownout has ended.

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