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UPS battery backup

Minutes: ride through a flicker, or shut down cleanly.

24 guides

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Portable power stations

Hours: a charged battery, with no fuel to store.

33 guides

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Portable generators

Days: as long as the fuel lasts, always outdoors.

57 guides

Best picks and comparisons

Start here

UPS battery backup

Minutes: ride through a flicker, or shut down cleanly.

Portable power stations

Hours: a charged battery, with no fuel to store.

Portable generators

Days: as long as the fuel lasts, always outdoors.

Guide 08 · UPS

How to Estimate Battery Backup (UPS) Runtime for Your Devices

Your UPS runtime depends on two things: how many watts your plugged-in devices actually draw, and the maker's runtime chart at that load. Measure the load, find it on the chart, and plan for less runtime as the battery ages.

Updated Drafted and checked with AIFact-checked by the HoldBackup editorial team How this guide was madeBased on manufacturer specs and owner reports, not HoldBackup's own testing.

On this page
  1. Step 1: Find the load you will put on battery
  2. Step 2: Read the runtime chart at your load
  3. Why real runtime is often shorter than the chart
  4. How to stretch the runtime you have
  5. Waveform, and when a UPS is the wrong tool
  6. Sources

Affiliate disclosure: some store links on HoldBackup are affiliate links. If you buy through one, HoldBackup may earn a commission at no extra cost to you. As an Amazon Associate I earn from qualifying purchases. How HoldBackup makes money

The verdict

Buy a sine wave UPS whose maker publishes a runtime chart, then confirm that chart shows enough minutes at the load you measured with your own devices.

See the store link

What we check

  • Runtime chart at your measured load
  • Watt rating above your total load
  • Number of battery-backed outlets
  • Output waveform for your devices
  • Replaceable battery and warranty terms
Compact tower UPS: upright unit on small feet with a narrow front display strip, a lit round power button and two vent slots on its side

Drawing of backup power equipment.

Store link UPS

CyberPower CP1500PFCLCD PFC Sinewave UPS Battery Backup and Surge Protector

One listing to compare. Check its specs against the list above before you buy.

Maker's US pageCyberPower's US page lists it with Purchase Online.cyberpowersystems.com Checked

What owners reportOwners report it works with home server and NAS shutdown software and lasts for years with fresh batteries. Forum owners also say the batteries can give out with no warning from the unit.TrueNAS forum, Unraid forum, The FPS Review forum Checked

PriceAmazon sets it, and it changes. The button takes you to today's price.

Store linkPaid link

The unit named above, on Amazon.

Check price on Amazon

HoldBackup earns a commission if you buy through this link. Amazon sets the price.

Step 1: Find the load you will put on battery

Runtime is set by what sits on the battery-backed outlets, not by everything plugged into the UPS. Many units also have surge-only outlets. Those protect against spikes but go dark in an outage, so they do not count toward runtime.

List every device you want running during an outage. Then find each one's power draw. The most accurate way is a plug-in watt meter, used while the device does its normal work. The label or power brick is a fallback, but it usually shows a maximum rating, so it will make your estimate look shorter than real life.

Add the numbers together. That total, in watts, is the load you will look up.

  • Check the device label or power brick for a watts or amps rating
  • Check the maker's spec page for typical power use
  • Use a plug-in watt meter for the real number during normal use
  • If your UPS shows current load on a display, read it with everything running

Step 2: Read the runtime chart at your load

UPS makers publish runtime charts or tables that show minutes of backup at different loads. Find your total on that chart. If your load falls between two rows, use the lower runtime to stay on the safe side.

For example, if your modem, router, and monitor read a combined 60 watts on a watt meter, find 60 watts on the maker's chart and read the minutes next to it. That is your starting estimate for a new, fully charged battery.

Also confirm your total stays under the UPS watt rating. UPS units list both VA and watts. The watt number is the limit that matters for your load.

Why real runtime is often shorter than the chart

Charts assume a new, fully charged battery at room temperature. Your real runtime will drift from that. Batteries lose capacity with age and heat, and a battery that was not fully recharged after the last outage will not deliver full runtime.

Load also changes. A computer draws more under heavy work than at idle, and devices you add later raise the total. Runtime does not fall in a straight line as load rises, so a small increase in load can cost more minutes than you expect.

  • Leave margin between your needed minutes and the chart figure
  • Recheck your load when you add or swap devices
  • Keep the UPS in a cool, ventilated spot
  • Test runtime occasionally by running on battery with your normal load

How to stretch the runtime you have

The simplest way to get more minutes is to put less on battery. Keep only what you need during an outage on the battery-backed outlets, and move printers, speakers, and extra monitors to surge-only outlets or another strip.

For a computer, set up automatic shutdown software so the machine saves work and powers down before the battery runs out. If you mainly want your internet up, a UPS carrying only the modem and router lasts far longer than one also carrying a desktop.

Waveform, and when a UPS is the wrong tool

Many desktop computers use power supplies with active PFC. These tend to run best on a UPS with sine wave output, which is why a unit like a PFC sinewave model is a common choice for computer setups. Check your device maker's guidance if you are unsure.

A UPS is built to bridge short outages and give you time to shut down safely. If you need hours of backup, a portable power station or a generator is usually the better fit.

Sources

Recorded AI check: Sep 29, 2026. The sources below may include later additions. AI checks compare factual numbers and checkable claims with web sources; they do not verify every statement.

Best UPS battery backup for a home and APC vs CyberPower compare units from the makers' numbers. Every guide in this class is in UPS battery backup.

How this guide was made

  1. Drafted and checked with AI. An AI model wrote the draft from the guide's topic. A second AI pass looked for factual numbers to check against web sources. This does not verify every statement. A draft that fails the check is held for review.
  2. Fact-checked by the HoldBackup editorial team. On , a person on the HoldBackup editorial team reviewed this guide against its sources. That is a review of the writing, not a test of any unit.
  3. General guidance only. No prices, rankings, or test results, because we have none to back them. Check any number against the maker's own spec sheet.
  4. No lab tests, and we say so. HoldBackup has not run any unit named here.
  5. The store link is not a pick for this guide. It goes to a unit in this product class that this guide does not review. Check it against the list above before you buy.
  6. Labelled store links. A store button goes straight to Amazon with HoldBackup's affiliate tag. HoldBackup counts the click. A live button carries a "paid link" label, and the disclosure sits above the first one on every guide.

Questions

If I cut my load in half, will my UPS last twice as long?

Not exactly. Runtime does not change in a straight line with load, and lighter loads often gain more than you would expect. Read the maker's runtime chart at both loads instead of doing simple math.

Can I use the wattage printed on my power brick?

You can, but it is usually a maximum rating, so your estimate will come out on the short side. A plug-in watt meter used during normal work gives a more accurate number.

Do the surge-only outlets count toward runtime?

No. Surge-only outlets lose power in an outage. Only devices on the battery-backed outlets draw from the battery, so only those count toward your load.

How do I know when my UPS battery is wearing out?

Watch for shorter runtime during tests or outages and any battery warning from the unit or its software. Check the maker's guidance on battery replacement and your warranty terms, and retest runtime from time to time.

Where does the price button go?

Straight to Amazon. Amazon sets the price and availability, and both can change.

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