Two different jobs
People often lump these devices together, but they handle different problems.
A surge protector is designed to limit short spikes of excess voltage so they do not reach the equipment plugged into it. A backup power supply, often called a UPS or battery backup, contains a battery that keeps equipment running for a limited time when the wall power fails, so you can save your work and shut down properly. Many battery backups also include some surge protection, and many offer some conditioning for small voltage dips and rises, but the features vary by model.
A plain power strip is neither. It adds outlets and nothing more. Some strips look just like surge protectors, so read the label and packaging rather than guessing from appearance.
What they guard against
Power problems come in several forms:
- Surges and spikes. A brief jump in voltage, which can come from the power grid, from large appliances switching on and off, or from storms. Electronics may survive minor ones for years and be damaged by a bigger one.
- Sags and brownouts. The voltage drops for a short period. A computer may restart or freeze when this happens.
- Outages. Power disappears entirely. An unsaved document is lost, and a drive that is writing data at that moment can end up with damaged files.
A surge protector addresses the first problem. A battery backup addresses the other two, at least briefly. Neither is a guarantee. A very large event, such as a direct lightning strike, can overwhelm any consumer device, and manufacturers’ own materials usually say so. During a severe storm, unplugging valuable equipment from the wall is the most dependable step, which includes disconnecting cables that enter the building where sensible and safe.
How surge protectors wear out
This is the part most people miss. The internal parts of many surge protectors absorb energy each time they handle a surge, and they gradually degrade. A device that has taken several large hits, or many small ones over many years, may still deliver power to your outlets while no longer offering much protection. The outlets work, the switch works, and nothing signals that the protective part is gone.
Some models have an indicator light that shows when protection is active, or when it has ended. If yours has one, pay attention to it, and replace the unit when the maker says protection is gone. Without an indicator, a sensible approach is to replace a protector after a significant electrical event such as a nearby lightning strike, or after several years of use, even though the exact lifespan varies. Check the maker’s guidance for a recommended replacement period.
Choosing a surge protector by general rating
The packaging usually gives several figures. You do not need to memorize them, but you should understand what they mean in general.
- Energy rating. Often listed in joules, this indicates how much surge energy the device is designed to absorb. A higher number generally suggests more capacity before the protective parts wear out. Compare like with like, and treat the number as a rough guide.
- Clamping voltage. This is the voltage level at which the device begins to divert a surge. A lower figure is generally better, because less excess voltage passes through.
- Safety certification. Look for a mark from a recognized testing organization in your region. Avoid unmarked or unusually cheap units, as these can be a fire risk.
- Outlet count and spacing. Large adapters can block neighboring outlets, so check the layout.
- Build. A solid cord and sturdy housing suggest better construction.
Do not plug one surge protector or power strip into another. Daisy-chaining can overload the first outlet and creates a fire hazard. Also avoid plugging heat-producing appliances such as space heaters into a protector meant for electronics, since they can draw more current than it is rated for.
Choosing a backup power supply
A battery backup is rated mainly by how much load it can handle, usually given in volt-amperes and watts. Add up the power used by the equipment you plan to protect, and choose a unit with a comfortable margin above it. The labels on your equipment, or the maker’s specifications, list their power draw. If you are unsure, leave a generous margin or ask the maker or a qualified electrician.
Think about what you want the unit to do. For most home users the goal is not to keep working for hours. It is to give a few minutes to save files and shut down normally. A larger unit gives more runtime but costs and weighs more.
Things to remember:
- Plug in the computer and monitor, and consider the router and modem if you want your connection to survive a brief outage. Do not plug in printers, especially laser printers, which can draw heavy current. Check the unit’s manual.
- Batteries inside these units wear out, typically over a few years, and they will not hold a charge as long as they once did. Many units give a warning or a test option. Follow the maker’s advice on replacement, and dispose of old batteries properly. Our guide to battery disposal covers the general principles, and electronics recycling is the right route for the whole unit.
- Test the unit occasionally as the maker describes.
Desktops, laptops and where they fit
A desktop gains the most from a battery backup, because a sudden power loss turns it off instantly. A laptop has its own battery and keeps running through an outage, so a surge protector is often enough for it. Good battery care also helps a laptop when it spends most of its time plugged in, and constant charging is a separate topic. External drives, network equipment and printers also benefit from surge protection.
Surge protection is a layer of safety, not a substitute for backups. Even with perfect power, drives fail. Keep your important files safe with proper backup basics.