Guide
Home and office UPS backup
A UPS keeps a few important devices running for a short time when the power fails, and softens spikes and dips the rest of the time. For most homes and small offices, that means a computer, a router or modem, and maybe a monitor, not the whole room.
Rule of thumb
Use the plug map below: battery outlets for what must stay up, surge-only outlets for what can wait. Size by adding the watt labels on the gear you'll put on battery, then leave headroom. Expect minutes of runtime, not hours, unless you add an external battery pack the manufacturer supports.
What a UPS is for
Wall power fails, dips, or spikes. A UPS sits between the wall and your equipment. On battery it buys you time to save work and shut down cleanly. On wall power it can also even out minor voltage swings, depending on the design.
It isn't a generator and it isn't a whole-home battery. If you need hours of light and heat, that's a different product.
What to plug in
Most desktop UPS units have two kinds of outlets. The labels matter more than the brand name on the box.
- Battery backup outlets: computer, monitor if you need to see the shutdown, router or modem, VoIP phone base, NAS if you care about a clean shutdown.
- Surge-only outlets: printer, speakers, chargers, and anything that can wait until the power returns.
- Leave space on the battery side. A laser printer or a space heater on battery will empty the pack in moments and can overload the UPS.
How big it should be
UPS size is sold in VA and in watts. Watts are the number to compare with your gear. Add the watt ratings on the power bricks and nameplates for everything you'll put on battery outlets. Pick a UPS whose watt rating is higher than that sum, with room to spare for a future monitor or drive.
VA is often the big number in the model name. It's useful for comparing models in one brand's range, but watts are what your equipment actually draws.
We don't publish a one-size chart here. Loads differ, and the safe answer is the sum of your own labels plus headroom.
How long it will last
On a typical home-office load, many desktop UPS units last a few minutes to maybe a quarter of an hour. That is usually enough to save files and shut down. It is not enough to keep working through a long outage.
Runtime shrinks as you add load and as the battery ages. Manufacturer runtime charts, when they exist, are estimates for new batteries at a stated load.
After you set it up
Plug the UPS into the wall, plug your must-run gear into battery outlets, and charge it fully before you rely on it. Connect the USB or network cable if you want the manufacturer's software to shut the computer down when the battery gets low.
Run a self-test from the front panel or the software once it's charged. Learn what the beeps mean in your manual so an outage doesn't feel like a mystery alarm.
UPS versus a surge strip
A surge strip only clamps spikes. When the power fails, everything on it goes dark. A UPS keeps battery outlets alive for a short time. If your only goal is spike protection for a lamp or a charger, a surge strip is enough. If you need time to shut a computer down, you want a UPS.
When the battery wears out
UPS batteries usually last a few years. Heat and frequent outages wear them faster. When you see a replace-battery warning, or runtime collapses, search the model on the label on the back or bottom of the UPS. We only name a battery when the manufacturer's own list names one for that exact model.
A new battery that doesn't fix the unit may mean the UPS itself has failed. In that case, service or a new UPS is the honest next step.