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The Best Uninterruptible Power Supply (UPS) for 2019: Reviews by Wirecutter

An uninterruptible power supply, or UPS, is basically a surge protector, a battery, and a power inverter (which turns the battery’s stored energy into usable power) wrapped into one unit. The size of the battery dictates how long it can provide power, while the inverter dictates how much power it can output at any one time—often listed as volt-amps (VA) but more easily discussed as watts (W).

A small, inexpensive UPS is great for anyone that wants their home Wi-Fi and Internet to stay online during shorter power outages or brownouts. Unlike traditional phone service that works without power, Internet and digital phone service requires a broadband modem, which may have only a small battery backup—adding a UPS could provide hours of uptime in case you need to reach emergency services.

Larger UPS units with extra power and features can help keep home offices and workstations running during business hours, or for at least long enough to save work and safely shut down vulnerable equipment. If you have a lot of important data on hard drives in a desktop computer or network-attached storage, you may need a UPS so you can prevent your drives from losing data in the event of a sudden power outage. In some cases, a UPS can provide crucial backup power to home medical equipment like CPAP machines for a limited time.

But powering your home theater for a movie marathon during a storm is going to be less feasible and less affordable. If you need long-term power, the capacity to keep appliances like refrigerators plugged in, or to light up your whole house, off-grid solutions like backup generators or professionally installed battery packs are the way to go.

How we picked and tested

We started by considering 93 models from three leading companies: APC, CyberPower, and Tripp Lite. We’ve tested uninterruptible power supplies and surge protectors from these companies in the past, and all the power-product companies have long histories and reputations as reliable. Since a UPS is designed to be used in an emergency, choosing from a reliable brand is crucial to avoid buyer’s remorse at the worst possible time.

To whittle down such a massive list of candidates, we considered the most important factors that go into a great UPS:

Power management: We insisted that any UPS we tested use line-interactive topology, or automatic voltage regulation (AVR), a more advanced form of power management than that used by less expensive “standby” UPS models. AVR means that when power from a wall outlet briefly dips or surges outside of a specified range, a small transformer in the UPS acts like a buffer to compensate without relying on the battery; the UPS switches to battery power only when the transformer can’t handle the variation. This reduces wear and tear on the battery during frequent brownout conditions, prolonging its overall life and providing more-reliable power to sensitive gear like hard drives. Since AVR is available without a huge price premium, it’s a sensible feature to have to get the most from a UPS in the long term.

A UPS without some type of AVR is generally referred to as a “standby” UPS. That’s because the battery is always on standby, ready to jump in anytime the voltage from the wall outlet fluctuates outside a small predetermined range. A standby UPS is fine for many applications, but the battery inside may need to be replaced sooner, and it may not correct voltage fluctuations as quickly as an AVR model. We dismissed any standby models without testing them.

Battery capacity: Most UPS batteries are small, sealed, lead-acid batteries, not so different from a car battery. That makes them much cheaper than the lithium-based batteries in smartphones and laptops, but it’s also why they’re heavier and store less energy.

Manufacturers often publish run-time ratings that outline how long a UPS can keep various wattages running. Since most ratings are based on ideal conditions, we tested our top candidates at two different loads, 50 W and 300 W, to see how they managed in real-world use. Our 50 W load was meant to simulate powering a cable modem and Wi-Fi router. Our 300 W load is closer to a full workstation, as it adds a modern desktop (around 150 W), a 27-inch monitor (88 W maximum), and network-attached storage hard drives (60 W maximum).

Since the batteries will likely start to hold less energy at the three-year mark (and may hold noticeably less energy after the five years) most models we considered have replaceable batteries to extend the life of the UPS. Prices for name-brand replacements range from $30 to $60, and the process is simple enough for a novice to complete in just a couple minutes.

Power output: While battery capacity and runtime measure how long a UPS can supply power, the power output tells you how much it can power at any one time. Most models explicitly include their output in the name or model number in volt-amperes (VA). The smallest UPS models we found with the AVR feature we require output 650 VA, more than enough to run a modem and Wi-Fi router at home. For an upgrade pick, we looked for models with at least a 1,000 VA rating. VA ratings aren’t common in most people’s lives, but they’re power ratings along the same lines as the more-familiar watts (W). For a quick estimation when shopping, you can assume that a UPS’s wattage rating will be about 60 percent of its volt-amp rating. So a UPS rated for 685 VA can probably handle about 400 W. That’s plenty to keep a cable modem (25 W), Wi-Fi router (30 W), and laptop charger (65 W) up and running for a while.

Outlets: All outlets on a home UPS provide surge protection, limiting the amount of extra voltage that could reach and potentially damage anything plugged into them. But generally only half of the outlets will be connected to the battery backup in case of an outage—and are prominently marked as such. That’s why we focused on models that had at least eight outlets total, since you’ll have only four of them in a power outage. In most home offices, this shouldn’t cause a problem, but it does require some planning in terms of making sure the right things are plugged into the right outlets.

Power Quality: For each model we tested, we looked at the power output using a digital oscilloscope provided by Bitscope. This let us see how well the inverters in each UPS converted the DC energy stored into the battery into the AC power provided by the outlets. Specifically, the oscilloscope let us look at two aspects of power quality: which models introduced the least amount of electrical noise into the line, and how well the modified sine wave inverter in each model imitated the kind of power that comes out of a standard wall outlet. For our upgrade pick, we also required a pure sine wave inverter (see the next item).

Pure sine wave power: A modified sine wave (MSW) inverter turns the DC power stored in the battery into the AC power you need coming out of the outlets. Because MSW inverters are less expensive to make and work well for most devices, they’re the the most common type of inverter used in UPS units (including our top pick). But MSW inverters create only a close approximation of the kind of AC power that comes out of a wall outlet—it’s not quite the same. Most gadgets that charge with a power brick (including smartphones, tablets, and laptops) won’t care much, since the power brick does extra conversion anyway. But anything expecting AC power for moving parts like motors won’t work normally on an MSW inverter, and audio equipment can pick up buzzes of interference from them. And some home medical devices just won’t work with MSW power. In any of those cases, you need pure sine wave (PSW) inverters instead.

Pure sine wave inverters, and the UPS models that use them, replicate the smooth wave of power that comes from a wall outlet powered by a utility company. These inverters are more expensive to make and thus less common when it comes to inexpensive or occasional-use power sources. We’ve come across multiple online discussions discussing how to provide backup power for CPAP machines and whether MSW or PSW were better. We reached out to ResMed, makers of a variety of home respiratory care devices, to find out what they recommend. Amy Cook, the company’s marketing director, told us that many of the company’s newer products have power converters or even lithium-ion battery backups available. But if you plan on using a different power source, “older-generation PAPs (S8 and earlier) that are using modified sine wave inverters cannot power their respective humidifiers.” Given the importance, not to mention cost, of equipment like CPAP machines, we’d recommend you opt for a battery backup made by the same manufacturer, if available. If not, we prefer to stick to PSW inverters—like the one included in our upgrade pick—to avoid any problems.

Extra features: A basic UPS doesn’t need a lot of features to do its job, but other features we considered include status displays that show battery charge and remaining runtime right on the unit and power-management software that lets you monitor and manage a UPS (over USB) from your computer. Neither feature is crucial for a UPS in most homes—the power goes out and you know you have limited network or computer time to do what you need to do. But a status display is a nice-to-have feature that can help calm power anxiety, and power management software that works on any operating system future-proofs changes in your setup so that your UPS can be just as useful years down the line as it is the first day you plug it in.

Every UPS from a reputable brand comes with some basic surge protection built in, which is good because you can’t plug your UPS into a surge protector or plug a surge protector into a UPS. Unfortunately, most affordable UPS units don’t offer much protection compared with a dedicated surge protector. In previous tests, electrical engineer Lee Johnson took apart our UPS samples to examine their guts. Based on his assessment, we found that our picks should protect your equipment about as well, if not for as long, as basic surge protectors we’ve tested before.

Our pick: CyberPower CP685AVR

Our pick

The CyberPower CP685AVR is our first choice for anyone who wants a UPS to keep their home network and modem online during short blackouts. Unlike competitors at similar prices, the CP685AVR can compensate for quick voltage sags and surges without switching to battery, which helps prolong the life of the battery and provide more-reliable power. The four battery-backed outlets can keep basic home networking gear running for about an hour, and all eight outlets have basic surge protection to fit plenty of equipment day to day. No setup is required for the UPS to do its job, but anyone who wants to monitor power consumption or manage shutdown settings can do so over USB with a Windows, Mac, or Linux computer—the closest competitors offer software only for Windows.

Most people are looking for a UPS to solve one of three problems in a blackout: powering a digital-phone modem for contacting emergency services and loved ones, preventing damage to something that needs to be properly shut down, or passing the time until the electricity comes back. The CP685AVR can keep a combination of a common broadband modem and Wi-Fi router (about 50 W) on for about an hour. The runtime decreases if you add devices to the other two battery-backed outlets. Even though power outages have increased in some parts of the US in recent years, they tend not to last too long (PDF), so a basic UPS should get you by in even the most unreliable regions.

When a UPS battery kicks in during a power outage, it offers better value the longer it can last.

The “AVR” in the model name CP685AVR stands for Automatic Voltage Regulation, one of the power-management features we required. Many inexpensive UPS models don’t include this option, leaving out the transformer and instead functioning as “standby” backups that can only switch to battery. Even APC, a leading competitor, doesn’t offer AVR in any models available for a similar price. The closest competitor that does is the Tripp Lite AVR650UM, which we tested our top pick against.

When a UPS battery does kick in during a power outage, it offers better value the longer it can last. When we tested the CP685AVR with a 50 W load meant to mimic the power requirements of a broadband modem and home Wi-Fi router, it lasted 57 minutes before shutting down. The Tripp Lite AVR 650UM managed only 38 minutes in the same test. Given the similar prices, that’s a lot more value packed into the CyberPower model.

The CyberPower CP685AVR and competing Tripp Lite models have similar maximum outputs, 390 W and 325 W, respectively. There are other similarities, too. They’re nearly identical in size, each with eight outlets. Though all eight outlets offer surge protection, only four on either model are backed up by battery power during a blackout. That’s a common arrangement, and the outlets are clearly marked, so you just have to make sure that your most important gear gets plugged into the right outlets.

The pure sine wave from a residential wall outlet.

Modified sine wave inverters, like the one in the CP685AVR, provide power that mostly works the same as power from a wall outlet but looks very different when examined.

The modified sine wave of the Tripp Lite TLAVR650UM.

The pure sine wave from a residential wall outlet.

Modified sine wave inverters, like the one in the CP685AVR, provide power that mostly works the same as power from a wall outlet but looks very different when examined.

None of the keep-your-network-up models we tested, including our top pick, do a particularly great job of imitating pure sine waves with their MSW inverters, though the CyberPower waveform looked closer to what we’ve come to expect when examining many MSW inverters on an oscilloscope. If you think you might fall prey to the side effects of MSW, check out our upgrade pick below, which produces PSW power instead.

There’s no status display on the CP685AVR, but it’s rare to find a UPS in this price range that has one along with the other features we think are crucial, including AVR and a long runtime. The only feedback you’ll get when the power goes out is a double beep every 30 seconds, and a more-continuous alarm when you have less than five minutes of power remaining. But if your UPS is going to live near a computer, you can see more detail by connecting to it via USB and downloading the free CyberPower Power Panel application. You can use this software to see the battery’s charge and the UPS status, monitor power consumption, change the alarm settings, and even customize certain events like having your computer safely shut down automatically when the power goes out. CyberPower, TrippLite, and APC all offer this type of software for Windows computers, but only CyberPower offers a Mac version.

CyberPower’s AVR Series has user reviews dating back almost 10 years. Although we’ve become wary of user-review averages for some product categories, most users have found the CyberPower offering to be a solid UPS, which is about what you’d expect for a utilitarian device. All three companies we considered for this category—CyberPower, APC, and TrippLite—offer a three-year warranty on any UPS.

Flaws but not dealbreakers

The CyberPower CP685AVR is a simple UPS that focuses on providing power at a good price, but that means giving up some conveniences. In particular, it has only one button, which turns the unit on or off. That means there’s no way to mute the alarm that chirps when power goes off unless you attach it to a computer and use the free Power Panel application. Without a way to quiet it, the CP685AVR will chirp every 30 seconds when it’s providing power during an outage. It’s annoying, but a common design for basic UPS models like this one.

Runner-up: CyberPower CP800AVR

Runner-up

If our top pick is out of stock and you don’t need (or want to pay for) the extra output or pure sine wave power that sets our upgrade pick apart, get the CyberPower CP800AVR. It’s nearly identical to the CP685AVR, our top pick: It has the same automatic voltage regulation (AVR) power management we like, similar one-hour runtime when powering a modem and router during an outage, and even the same dimensions and design. The only difference is that the CP800AVR can deliver about 15 percent more power at any given moment during a blackout, which isn’t enough to make a huge difference in how you’d use it.

Since the CP800AVR uses the same size battery as our top pick, it’s no surprise that it lasted about as long in our testing. When fully charged, the UPS powered a 50 W load (similar to what you might need to power a broadband modem and Wi-Fi router) for an hour. As you plug in additional power-hungry equipment, that runtime will go down—all the way to just three minutes (PDF) when fully loaded.

For the CP800AVR, a full load is 450 W, compared to 390 W for our top pick. That’s a small difference, especially since ideal setups will only use half that maximum to help maintain battery life in the long run. That brings the 60 W difference down to a real-world difference of just 30 W—less than what most laptop chargers use. If you need more power during an outage, you’re better off with our upgrade pick, which is rated for 600 W and adds additional benefits like pure sine wave power, extra outlets, and a status display.

The CP800AVR shares the same design and outlets (eight, four with battery backup) as our top pick, the CP685AVR. It also similarly lacks a status display to monitor the battery level, but you can use the CyberPower Power Panel application on a Windows, Mac, or Linux PC connected via USB to monitor the UPS and make minor tweaks like silencing the alarm.

The pure sine wave from a residential wall outlet.

The CP800AVR uses a modified sine wave inverter to turn the DC power in the battery to a rough approximation of standard AC power.

The APC BR700G is a modified sine wave inverter as well, though it does a better job at smoothing out its peaks and valleys.

The pure sine wave from a residential wall outlet.

The CP800AVR uses a modified sine wave inverter to turn the DC power in the battery to a rough approximation of standard AC power.

As was the case with all of the more-affordable UPS models, our runner-up uses a modified sine wave inverter that will work fine for most electronics with a power brick—including phone chargers, laptops, routers, and modems—but may cause problems for sensitive electronics like audio gear or home medical equipment. When we showed the waveforms recorded from our two top picks to Lee Johnson, an electrical engineer with whom we frequently collaborate, he noted slight differences in the two and suggested that the CP800AVR may have some sort of extra filter before the outlet. But Johnson agreed that there’s no evidence that the slight difference would have an impact on most devices. If you’re concerned about that, you need a pure sine wave inverter like the one inside our upgrade pick.

Upgrade pick: CyberPower CP1000PFCLCD

Upgrade pick

If you need more power, more outlets, or to power sensitive electronics like audio or home medical equipment in a blackout, the CyberPower CP1000PFCLCD is the best choice. It costs around twice the price of our top pick, but it can keep a desktop computer setup running long enough to shut down safely, includes an upgrade to pure sine wave (PSW) power, adds an LCD status display to the front and two more outlets to the back, and has an output roughly 50 percent higher when the power goes out. The battery is roughly the same size as our top pick’s, though, so it won’t last much longer when powering the same devices.

Like our top pick, and any of the pure sine wave models we considered, the CP1000PFCLCD uses automatic voltage regulation (AVR). By putting less wear and tear on the battery, AVR should help to extend the overall life. And when it is time for a replacement, name-brand batteries cost around $35 and take a few minutes to swap in without any tools.

The CP1000PFCLCD is smaller than many workstation UPS units, which means that its battery is smaller than what you get with some competitors and won’t keep you running much longer than our top pick given the same load—a 50 W router and modem combo should last around an hour. And while it can handle a desktop computer, display, and a few accessories, in our tests, it could power a 300 W load for only about eight minutes. That’s enough time to shut down computers and hard drives safely, but definitely not enough to keep you working through a bad storm. (The APC BR1000MS, which sells for a similar price, has a larger battery inside and is rated to last around 50 percent longer than our pick, but an annoying flaw kept us from recommending it.) In contrast, the largest CyberPower UPS in this line is rated for nearly twice the runtime of our pick, but at over $200, we’re not convinced it’s a good value or a necessity for most people. With 300 W of gear plugged in, the larger unit is rated to last only 19 minutes, 10 minutes longer than our pick’s rating. My own survey of popular CPAP machines showed that most use between 30 W and 100 W, depending on the settings. That’s a big range, but a CPAP in the middle of it would likely last around 45 minutes connected to our upgrade pick.

The more gear you have plugged in, the less runtime the battery will provide. The CP1000PFCLCD is rated to put out 600 W at any one time, but we never recommend running a UPS at a full load. Not only do you risk overloading it—causing the UPS to shut down, trip its breaker, or in severe cases damage it—but larger loads will wear out the overall battery life faster. Besides, if you put 600 W of gear on this model, the battery would conk out after just three or four minutes.