This post was done in partnership with The Wirecutter, a buyer's guide to the best technology. Read the full article with more details and background information here.

Surge protectors don't last forever. Like lightbulbs, they need to be replaced every few years when they wear out. Just because your old surge protector passes power to your devices doesn't mean it's still actively protecting them—in fact, you probably need a new one. After assessing more than 30 hours of research, and 32 hours of testing by an electrical engineer, we found that most surge protectors that cost just above $20 will provide adequate protection from surges. Our extensive research and testing showed that more-expensive units didn't provide enough additional benefit to be worth their higher cost. And of the units we tested, our top pick is the 10-outlet Tripp Lite TLP1008TEL, because it stops passing power when it's no longer effective at blocking surges.

Most surge protectors rely on an easily ignored LED indicator to tell you when they've ceased protecting your gear. We picked the TLP1008TEL because when its ability to block surges wears out, it cuts the power off entirely. So long as your devices are energized, you know that surge protection remains in place and have no ambiguity as to when it needs to be replaced.

If this Tripp Lite is unavailable, the Belkin PivotPlug is also a capable surge protector and has an excellent design that offers more outlets at a similar price. But, unlike the Tripp Lite, it still provides power even after the protection ceases being effective, alerting you by the failure of an indicator LED. You might prefer a unit that functions this way if you're plugging in hard drives or other sensitive electronics that you fear might be harmed by a sudden shutdown, but for most people this won't be a concern. With a total of 12 outlets, the Belkin model includes eight tilting outlets along its sides that allow you to fit all manner of power blocks at myriad angles.

For lighter duty, like under night stands or side tables, the Accell Powramid D080B-015K is the way to go. It has two USB ports and six outlets that are usable even with larger plugs, all in a comparatively small package. The USB ports put out a combined 2.1 amps, enough to charge one smartphone or tablet at high speed or two devices at low speed. Due to the Powramid's small size, Accell used a compact circuit that might not last quite as long, but offers a great deal of protection. Even at their lower price, Accell products safely prevent power from passing through when the protection fails—you'll know when it's time to replace it in a few years.

Tripp Lite's SpikeCube is perfect for traveling in areas with spotty grids. It covers just one outlet, but has performance comparable to that of the bigger picks squeezed into a pocketable package. If you want something on the go with more outlets than the SpikeCube and you are less concerned about surge protection, check out our full travel USB surge protector guide.

Who this is for

A surge protector offers peace of mind when you're concerned about sudden power spikes that could fry your expensive electronics. You may live where severe weather regularly causes power fluctuations (though a surge protector won't help you in the event of a direct lightning strike), or be on an electrical utility's system that can't provide good, consistent power. You may also just want figurative insurance—more about actual insurance later—against an unlikely event that requires a small investment to forestall.

Because a surge protector is a "better safe than sorry" device, experts recommend getting one that stops providing power the moment the internal circuitry that protects against surges stops working. For most people, that isn't a problem, because most modern hardware can cope with the sudden loss of power—and better the loss of a power strip than the destruction of hardware that could cost thousands of dollars to replace.

However, if you have equipment that could be damaged by a sudden loss of power or mission-critical gear that can't ever go down or that needs a specific shutdown or power-up sequence (a hard disk drive, for example), you shouldn't be looking at a surge protector at all. Instead, you want a uninterruptible power supply, or UPS. A UPS is basically just a big battery that you place between your outlet and your gear, and most of them have surge protection built in.

If you live in an area with a stable power grid and a mild climate, you can probably skip the surge protector without too much risk. Ultimately, though, the low cost of surge protectors makes them worthwhile for a vast majority of people looking to stave off this one type of catastrophe.

How we picked

Many home office and home theater surge protectors come with ports that promise to protect your cable or phone lines, but we feel comfortable without them on our main pick. Though phone and cable lines certainly can carry surges into your home, many technicians and Internet providers discourage running data lines through surge protectors because, they say, it can introduce noise and degrade performance—a claim we weren't able to prove or disprove. In any case, our testing and tear-downs showed many manufacturers put wimpier protection (if any at all) on these auxiliary ports, so skipping them probably puts your modem or cable box at only slight risk.

Noise filtering is a common "premium" feature on the more-expensive surge protectors, but because most models performed similarly last year, we didn't test it on this year's models. In any case, all power supplies, whether internal or external, have noise filtration built in—in most cases, enough already to prevent any noise coming in on the AC line from interfering with the operation or performance of your electronics. Noise filtration probably isn't something you need to worry about unless you're having some sort of noise problem (usually manifested as static) in your audio or video gear or computer peripherals.

Though many surge protectors are sold with "connected equipment coverage," we didn't consider that in making our selections. We suggest you read the fine print because often you'll have to leap through a bunch of hoops to collect in the event of disaster. If you want financial protection you can count on, don't get it from a tech manufacturer. Just make sure to double-check that your electronics are covered by your homeowners policy or renters policy.

If your home theater costs more than a compact car, series mode protection may be worth investigating, but the technology isn't worth the huge price tag for most people. These surge suppressors are made by companies like Brickwall and Torus Power, and came on the market much more recently than the metal oxide varistor (MOV)-based protectors that we considered. Series mode protection is superior to MOV-based protection on pretty much every point, except for one big one: cost.

It would cost more than 10 times as much to replace our MOV-based pick with a similar number of series mode protected outlets from a reputable manufacturer. Though the series mode protector will theoretically pay for itself after 30 to 50 years (depending on how surge-prone your abode is), the upfront cost is simply too high to bear for most people. Spending $300 on a device to protect $2,000 worth of equipment from a rare disaster scenario is not worth it. We think it makes more sense to spend roughly $20 for a device that stops passing power when it's kaput and then replace it every few years.

Once we had a good idea of what features we could leave out, we surveyed 835 of our readers to learn about their expectations and narrow the criteria. Most of our respondents have six to seven devices plugged in, but wanted between eight and 12 outlets in a full-featured new unit, and were willing to spend up to $50. Features like USB outlets were less important than designs that accommodate bulky power supplies.

For lighter-duty use, our survey respondents generally had just three or four devices in use and the desire for a couple more, so we focused on units with six outlets that sell for less than $30. The smaller, lower-powered chargers used in a bedroom are less likely to have huge power bricks, so outlet spacing is less important than useful perks like USB ports.

We reached out to the manufacturers to verify clamping voltage, response times, and failure behaviors on top models, and after all that our final test list comprised the Belkin Conserve, the Belkin PivotPlug 12-Outlet BP112230-08, the APC P11VNT3 3020J 11-outlet SurgeArrest, the Tripp Lite TLP1008TEL, and the Tripp Lite Isobar HT10DBS for office and home theater use; and the Accell Powramid, the Accell Power Genius, and the Belkin PivotPlug 6-Outlet for bedroom and light-duty use.