How Old Is Your Surge Protector

If your surge protector is more than two years old, there is a good chance that it's time to replace it as they have a definite lifespan. Every time it does its job, it takes a little more damage and wears out a little bit more. At some point in time your surge protector will stop protecting your gear from power surges and become a simple power strip or worse.

When worn out, a surge protector can actually start passing voltage incorrectly (something I know from personal experience). It’s hard to tell when a surge protector loses its ability to protect the gear plugged into it, so, if you’re still using an old surge protector you purchased ten years ago, it’s probably long past the time to replace it. A surge protector is designed to catch power spikes (high voltage that could potentially damage your electronic equipment) before it does any harm to the equipment plugged into it, but there’s nothing a surge protector can do about low voltage issues.

Most surge protectors also function as a power strip, providing additional electrical outlets for you. If you’re connecting your computer, modem router, television or other gear, there’s a good chance you will want some extra electrical outlets anyway and a power strip that’s also a surge protector will provide those outlets. You can find simple power strips that offer no surge protection as well, but with the difference in price between a plain power strip and a surge protected power strip being minimal, you're better off spending a few dollars more for the surge protected variety. As inexpensive and simple to install as they are, it's never a bad idea to ensure all of your expensive electronic equipment is connected to the power through one.

Surge protectors don’t last forever. When a voltage spike from the electrical outlet they are plugged into passes through one, your surge protector is designed to absorb that excess voltage so your equipment doesn't. When this happens, it has to do something with that extra voltage to protect any devices connected to it. To do this, a surge protector uses a component called an MOV (metal oxide varistor). When the voltage spikes, the surge protector sends that extra voltage through the MOV. The MOV breaks down a little (or a lot, depending on the severity of the voltage spike) each time it is forced to do its job so the excess voltage doesn't damage your devices. Each time the MOV is forced to do this, whether from small increases in voltage or large ones, the surge protection offered by that MOV is lessened. In other words, your surge protector can only absorb so many surges before it stops functioning as a surge protector and starts functioning as a plain old power strip (or worse) which will allow everything through to your devices.

A surge protector is rated in joules (a measurement of energy) and the higher the rating, in joules, the more protection it provides. But, keep in mind that it's going to degrade with every voltage spike and higher voltage spikes will cause more of that degradation than smaller ones. This will go on until that surge protector is completely worn out. It's all cumulative. For example, if you were using a surge protector rated for 1000 joules and there is a 999 joule spike on your electrical lines, that surge protector is pretty much worn out, but if the voltage spike you are being protected from is only in the 10 joule range, you could handle about 99 more of those before your surge protection is completely gone. Since it is impossible without some specialized and expensive equipment to determine exactly how high the spike that hit your home was, it's probably not a good idea to wait around until you've experienced 990 electrical events before investing in some new protection.

Just for comparison purposes, this, from the University of Illinois Department of Physics:

     “The energy of an average 3 mile long lightning strike is one billion to ten billion joules. To keep a 100-watt light bulb going for one second, one hundred joules of energy will be used. With one billion joules, the light bulb will be lit for 116 days.” And since the sheer amount of power in a lightning strike is so high, even the best, non-commercial surge protector isn't going to help. I was unable to find any information about how much power is coming through your electrical lines during the kind of voltage spike associated with a transformer going out or being reconnected, but I'm sure we can assume it's going to be very substantial. Maybe not like a lightning strike right outside your house, but significant just the same.

How do you know when it's time to replace it?

It is very difficult, almost impossible, to tell when a surge protector has taken so many hits that it is time to replace it. Some surge protectors have built in lights that are designed to alert you to this problem and inform you when the protector needs to be replaced and, in a perfect world, you could depend on that. I wouldn't, though. Remember that each high voltage event breaks down the MOV in that surge protector a little more than the one before and, without that specialized, expensive equipment mentioned above, you just can't be sure how much “life” yours has.

Obviously, if your surge protector is indicating that it is no longer protecting you, it's time to replace it. Don’t ever assume that the surge protector you've been using for the last 5 years is still working properly because a warning light hasn’t come on. What you can assume is that, the older it is, the more likely it needs to be replaced and with the electrical events we've experienced around here in the last year, it would be a good idea to assess your present risks. Anytime your surge protector has absorbed a serious power spike (like those caused by lightning nearby) you should replace it immediately.


There really isn't an exact lifespan (as measured in time) of a surge protector. It all depends on its original rating (in joules) and how much energy it has been forced to absorb. As a simple precaution, in areas prone to high electrical variances, many people recommend replacing your surge protector every two years. Not a bad idea, but remember that even then, depending on how highly rated your surge protector was when originally purchased, how many times it has taken a hit, how hard those hits were and how long it has been taking them is what really determines when it is time to replace it or not. And, do you really know all of those factors?