Snohomish County Public Utility District No. 1

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Surge Protection for Your Home

Where do surges come from?

Most power surges originate inside your home or building and result from motorized or “noisy” equipment. Some surges originate outside your home or building and result from weather, animals, neighbors, traffic accidents, utility equipment malfunctions, and so on. Surges can enter your home through power lines, phone lines, or cable TV connections.

The problem:

The microprocessors and other sensitive circuitry in most modern appliances and equipment – like personal computers, microwave ovens, stereos, televisions, VCRs, and fax machines – make them easily damaged by power surges. Equipment can be ruined in one hit, such as during a lightning or wind storm, or it can be damaged little by little over time.

The solution:

Plug your sensitive equipment into a surge suppressor. It’s an inexpensive “insurance policy” for your valuable equipment.

Features to Look for in a Surge Suppressor:

To ensure adequate protection, look for devices with these four specifications, at a minimum:

1. UL 1449 Listed

  • Conform to Underwriter Laboratory's standard UL 1449 for transient voltage surge suppressors (TVSS).
  • UL 1449 Listing is required for safety; UL Listing as a “power tap” is not sufficient.

2. Peak Surge Current

  • 39,000 amperes or more.
  • Higher is better.
  • Sometimes called Maximum Transient Current or Maximum Surge.

3. UL 1449 Suppressed Voltage Rating

  • 330 volts gives the best protection.
  • Higher voltage ratings give less protection.
  • Sometimes called Clamping Voltage.

4. Energy Rating (Joules)

  • 420 joules or more.
  • Higher is better.
  • Because testing methods for Energy Rating are not standardized, you shouldn't base your choice on Energy Rating alone.

General FAQs:

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What if the packaging doesn't list all these specifications?

Consider buying a different surge suppressor that lists all of the minimum specifications and make sure the device you choose is UL 1449 Listed. Expect to pay at least $30 for a good surge suppressor.

What can't a surge suppressor do?

It cannot protect you from power outages (black-outs) or power sags (brown-outs). It also cannot protect your equipment from nearby lightning strikes.

What about my older home?

Surge suppressors work only if they are plugged into a properly grounded 3-prong outlet. If your house is older and has 2-prong outlets or improperly grounded 3-prong outlets, have a licensed electrician upgrade your outlets.

What about my old surge suppressor?

UL Standard 1449 became stricter in August 1998. Older surge suppressors may be less safe. If you do not see "UL 1449 Listed" stamped or embossed on your device, it may just be just an outlet strip on an extension cord, not a surge suppressor. Replace an old surge suppressor if it is discolored, overheats, or shows signs of melting. If your old surge suppressor has no indicator lights, it may not be working and should probably be replaced.

Other Information to Consider:

Appropriate Connectors & Outlets

  • An outlet for each piece of equipment.
  • Room for AC adapters (transformers).
  • If you are protecting a TV, VCR, telephone, fax, or computer, get a surge suppressor with TV cable connections and/or phone jacks.


  • Status or warning lights to indicate that the device is working (not just that it's on).
  • Sound alarm to indicate surges.

Electrical Noise Protection

  • For EMI (electromagnetic interference).
  • For RFI (radio-frequency interference).

Warranty & Insurance

  • Warranty on surge suppressor of at least 5 years.
  • Warranty on connected equipment of $2,500 to $25,000 or more.