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UPS battery backup

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

24 guides

Best picks and comparisons

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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 21 · UPS

UPS VA vs Watts: How to Read a Battery Backup (UPS) Rating

Size a UPS by its watt rating, not its VA number. VA is usually the bigger figure on the box, but watts tell you how much real load the unit can carry. Add up your devices in watts, leave headroom, then check the maker's runtime chart at that load.

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. VA and watts are two different limits
  2. Find your own load in watts
  3. Watts set the ceiling, the runtime chart sets the minutes
  4. Other checks on the spec sheet
  5. Common sizing mistakes
  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 UPS whose watt rating sits comfortably above your measured load, and let the maker's runtime chart at your own wattage decide between models.

See the store link

What we check

  • Watt rating above your measured load
  • Runtime chart at your load
  • Output waveform (pure sine or simulated)
  • Battery-backed vs surge-only outlets
  • Outlet count and spacing
  • Warranty and battery replacement 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.

VA and watts are two different limits

Every UPS lists two ratings. VA, or volt-amperes, is apparent power: voltage times current. Watts are real power: the work your devices actually do. Because of how electronics draw current, the watt figure is usually lower than the VA figure.

A UPS has to stay under both limits. In practice, the watt rating is the one you hit first with modern electronics, so it is the number that decides whether a unit can carry your load.

Some boxes print the VA number large and the watt number in small type. If you only see VA, look up the spec sheet before you buy. A UPS without a clear watt rating is hard to size.

Find your own load in watts

Do not guess. Draws vary by model, so get the number from your own gear.

For example, if your computer, monitor, and router add up to 300 watts on a watt meter, you want a UPS whose watt rating is well above 300, not one whose VA rating is 300.

  • Check the label on each device or its power brick.
  • Look up the maker's spec page for the exact model.
  • Use a plug-in watt meter to measure real draw while the device is busy.
  • Add every device that will plug into a battery-backed outlet.
  • Leave headroom so the UPS is not running at its limit.

Watts set the ceiling, the runtime chart sets the minutes

The watt rating tells you the most a UPS can carry. It does not tell you how long it will last. Runtime drops as load rises, and the drop is not a straight line.

Find the maker's runtime chart or calculator and read it at your measured wattage. For example, if your load is 300 watts, look up the minutes listed at 300 watts, not at full load or a light load.

If the minutes are too short for your needs, a larger UPS helps, but for outages lasting hours a portable power station or generator usually serves you better.

Other checks on the spec sheet

Once the watt rating fits, compare units on how they deliver power. The listing on this page, the CyberPower CP1500PFCLCD PFC Sinewave UPS, lists sine wave output in its name. Confirm the watt rating, outlet layout, and runtime on the maker's spec page before you order.

  • Waveform: pure sine wave output is the safer choice for computers with active PFC power supplies. Check your power supply's spec if unsure.
  • Outlets: many units split outlets into battery-backed and surge-only. Put critical gear on the battery side.
  • Spacing: count how many large power bricks will fit side by side.
  • Display and software: a screen or USB link that shows load and runtime helps you confirm your sizing.
  • Warranty: check the length and whether the battery is covered and replaceable.

Common sizing mistakes

Most sizing problems come from reading the wrong number or skipping the measurement.

  • Buying by VA alone and overloading the watt limit.
  • Using a device's maximum rating as its typical draw without measuring.
  • Plugging a laser printer or space heater into a battery outlet.
  • Expecting the full rated load to run for long on battery.
  • Forgetting that batteries lose capacity with age, so new-unit runtime will shrink.

Sources

Recorded AI check: Oct 5, 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

Which number matters more on a UPS, VA or watts?

Watts. Size the UPS so your measured load in watts sits comfortably below its watt rating. The VA rating is usually higher and can make a unit look bigger than it is for your load.

Can I convert VA to watts myself?

Not reliably, because the ratio depends on the UPS design. Use the watt rating the maker publishes on the spec sheet. If no watt rating is listed, choose a different unit.

How much headroom should I leave?

Enough that the UPS is not running at its limit. For example, if your load measures 300 watts, choose a unit whose watt rating is clearly above that, then confirm the runtime at 300 watts on the maker's chart.

Does a bigger UPS mean longer runtime?

Often, but not always. Runtime depends on battery capacity and your load. Compare models by reading each maker's runtime chart at your own wattage.

Where does the price button go?

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

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