Surge protectors are electronic devices designed to protect appliances such as computers and audio visual equipment from damage in case of an electronic power surge. Lightning can cause these surges, or electrical equipment failure.

Surge Suppressors and Power StripsAPC PER7T surge protectorCredit: Amazon

Some of these protectors are no more than power strips with multiple outlets that offer little protection from a power spike. The surge suppressor should be commensurate with equipment it’s protecting. There are several things that determine how much protection a surge protector offers electrical appliances.

Surge suppressors come in a variety of configurations and prices. The more expensive have more features, but a modestly priced unit can offer satisfactory protection.

Underwriter Laboratories (UL)

Surge suppressors should meet Underwriter Laboratory’s standard UL 1449. It should also have this rating for clamping voltage.


The joule rating indicates how much energy the protector can absorb before it fails. It indicates how much energy is absorbed and dissipated before system overload. A minimum joule rating of 200 – 400 is required. A rating of 600 and higher is recommended.

Peak Amps

This is similar to the joule rating, but more accurate. It is the peak surge current, and the suppressor should be rated at least 200 amps and higher is better.

Clamping Voltage

The clamping voltage is the amount of excess voltage that triggers the suppressor to restrict the incoming over voltage. The lower the clamping voltage offers better surge protection. A 330 rating is good for a television, but less is better for computer equipment. The Underwriters Laboratories (UL) do a 500-amp test. Check that the surge protector reflects these results.

Let Through Voltage

This is the amount of voltage that passes through to the equipment. UL standards use 330 as the standard.

Response Time

The lag or response time is the time it takes for the protector to react to a sudden power spike. A surge protector should respond to the spike in less than one nanosecond. The best are capable of a few picoseconds. A nanosecond is a billionth of a second, and a picosecond is a trillionth of a second. Even with the best surge protector with the shortest response time, it’s possible for the spike to let enough electricity through to damage appliances.

Phone, Cable and TV Protection

Phone lines are susceptible to power spikes. A modem and fax is vulnerable if connected to telephone lines. A good surge protector will protect them from spikes


The warranty should be for at least five years. The best offer coverage of $10,000 to $20,000 on equipment.

Higher end surge suppressors have more features and options, but a moderately priced unit will provide proper protection. A modestly priced surge protector will better protect equipment than a power strip. The quality of surge protectors varies between models. Appliances such as computers require higher standards than a television.