A surge protector blocks sudden spikes of voltage so they don’t fry your electronics. A UPS (uninterruptible power supply) does that too, but it also has a battery that keeps your gear running when the power cuts out. So the real difference between a UPS and a surge protector is the battery.
Let’s look at what each one does, and when you’d want one over the other.
What a surge protector does
A surge protector is basically a power strip with protective parts inside. When the voltage jumps, those parts divert the extra energy so it doesn’t reach your devices. It costs little and has no battery to replace.
It can’t do anything about a blackout, though. When the lights go out, so does everything plugged into it. And it doesn’t smooth out brief dips in voltage, either.
What a UPS does
A UPS sits between the wall and your equipment, holding a battery ready. If the power drops, it switches over in a fraction of a second, so your computer never notices. That gives you a few minutes to save your work and shut down properly.
Most models also include surge protection built in. Better ones even correct small voltage sags and swells, which is handy if your lights flicker during storms.
What each one protects against
| Problem | Surge protector | UPS |
|---|---|---|
| Voltage spikes | Yes | Yes |
| Total power outage | No | Yes, for a short time |
| Brief dips or flickers | No | Yes |
| Voltage sags and swells | No | On many models |
| Needs battery replacement | No | Every few years |
When a surge protector is enough
If a sudden power cut wouldn’t cost you anything, a surge protector is fine. That includes a lamp, a TV, a phone charger or a printer. Nothing’s lost if they shut off, so there’s no reason to pay for a battery.
When you want a UPS
Now think about your desk. Say you’re typing a long report or in the middle of a video meeting when the power blinks. Without backup, your computer restarts and your work may be gone. A UPS protects against exactly that.
- A desktop computer with unsaved work
- A modem and router, so your internet stays up
- A network drive or storage device that can be damaged by sudden shutdowns
- Any equipment you’d hate to reboot in the middle of a task
Our guide to the best UPS battery backup for home office use is a good starting point. Short on desk space? The best compact UPS battery backups for home office list keeps things small, and the best affordable UPS battery backups for home offices picks help if you’re watching costs.
Do you need both?
Usually, one device does the job. Because most UPS units already include surge protection, you don’t need to stack a surge protector in front of one. In fact, plugging a UPS into a power strip is often discouraged by manufacturers, so plug it straight into the wall.
The sensible setup is this: UPS for the computer and network gear, surge protectors for everything else. That way each device gets the protection it needs, and you’re not buying batteries for a lamp.
Reading the labels when you shop
Both products come with a pile of numbers, and it’s easy to feel lost. Here’s what to look at.
- Joule rating (surge protectors): this shows how much energy the unit can absorb before it wears out. Higher is better.
- Watts and VA (UPS): the watt rating tells you how much gear the unit can power. Add up what you plan to plug in, and choose a unit with room to spare.
- Outlet count and spacing: bulky power adapters can block neighboring outlets, so check the layout.
- Indicator lights: a surge protector’s protection light shows when its protective parts have worn out. If it goes off, replace the strip.
Surge protectors wear out
Here’s something many people don’t know. A surge protector absorbs energy every time it takes a hit, and eventually it can’t protect anymore, even though it still passes power. It looks fine and works as a regular power strip, but the protection is gone. If a big storm or a power event happens near you, think about replacing it, and don’t count on one that’s many years old.
Protect the lines, too
Spikes don’t only come through the wall outlet. They can arrive through the cable or phone lines that connect to your modem or router. Many UPS units and surge protectors have ports for that line. If yours does, run the line through it. It’s a small step, but it closes a gap.
A simple setup for most desks
- Plug a UPS into the wall.
- Connect your computer, monitor, modem and router to its battery outlets.
- Put your printer and lamp on a surge protector in a different outlet.
- Test the UPS now and then.
Frequently asked questions
Does a UPS replace a surge protector?
For the devices plugged into it, yes. Most UPS units have surge protection built in, so a separate one isn’t needed for those devices.
How long does a UPS keep my computer on?
Usually a few minutes to a bit longer, depending on the load. It’s meant to give you time to save and shut down, not to work through a long outage.
Can I plug a laser printer into a UPS?
It’s best not to. Laser printers draw a large burst of power and can overload a UPS. Use a surge protector for the printer instead.
The bottom line
A surge protector guards against spikes; a UPS guards against spikes and outages. For anything where losing power means losing work, choose a UPS, and use surge protectors for the rest. To work out the right capacity, our guide on what size UPS you need for a home office walks you through it.