How Many Joules Does My Surge Protector Need?

 November 20, 2023 |  4 minute read time

Among the factors to consider when choosing a surge protector—outlet count, optimal cord length, etc., the most important factor may be the joule rating.

Karenann Brow

What Are Joules?

A joule is a measure of energy released over a period of time. For example, an average lightning strike releases about one billion joules of energy over a fraction of a second.

A surge protector joule rating indicates how much energy it can absorb before it fails. The higher the number of joules, the greater the surge protection provided. Keys to determining the amount of protection needed include the type and value of the equipment to be protected.

Valuable Equipment Needs a Higher Joule Rating

You may be wondering, “How much surge protection do I need?” The answer depends on whether you are protecting a $500 PC or a $5,000 home theater. Obviously, the higher the value of your equipment, the higher the surge protector joule rating required. While any device that gets plugged into an AC outlet can benefit from surge protection, inexpensive components such as lamps, digital clocks and blenders don’t need a high level of protection.

A unit with up to 1000 joules of surge protection is adequate for these small electronics. Some components have sensitive circuitry requiring protection, but don’t store extensive data. Units with surge protector ratings of 1000 to 2000 joules will provide sufficient protection for power tools and office equipment such as printers, copiers and routers. Consider the highest joule ratings—2000 and above—for home theater components, gaming consoles and any computer that stores important data… anything from customer lists to financial information to irreplaceable photos and personal records.

Location is also a Factor

In areas with frequent lightning storms, a higher level of protection is required. However, Mother Nature alone doesn’t create all the surges playing havoc with your electronics. Problems at the utility company can also create power spikes. Within industrial areas, tools and heavy equipment can cause damaging surges and line interference too.

Even in the quietest residential neighborhood, up to 80 percent of all surges originate inside the home or office. When power tools start up, when the air conditioner cycles on and even when the refrigerator or oven kicks on and off, small surges you may not notice can strike your electronics. A whole-house surge protection system will not prevent these types of voltage spikes.

How a Surge Protector Works

When the voltage rises above the acceptable level, the surge protector suppresses the excess voltage to prevent it from causing harm. Specifically, internal components called metal oxide varistors (MOVs) absorb the excess voltage and divert it safely to the ground wire, preventing it from reaching the connected equipment.

How a surge protector works

Is Your Surge Protector Still Working?

Surge protectors don’t display how many joules of protection are available, but most models include an LED that lets you know protection is present. However, these lights might be ignored or are out of sight when the surge protector is located behind furniture or under a desk. No surge protector lasts forever. If you’ve had a major electrical event, such as lightning that caused a power failure, or if your units have been in use for a few years, today is a great time to make a small investment in new surge protectors and greater peace of mind.