UPS Battery Backup: VA Rating and Runtime for a Home Office

Watts, not VA, decide what the unit can run

Every unit here is sold under its VA number, and four of them share a 1500 VA badge while publishing two different watt ratings. The APC BX1500M, APC BR1500MS2 and Eaton 5S1500LCD are each rated 900 W. The CyberPower CP1500PFCLCD is rated 1000 W. The watt figure is the one your equipment has to clear. Add the rated wattage of your desktop’s power supply, your monitor, your modem and your router. That total is the number to check against the watt rating.

The three smallest units are rated 450 W (APC BE850M2), 510 W (CyberPower CP850PFCLCD) and 550 W (Amazon Basics ABMT1000). The 1500 VA units buy headroom above those figures, and they bring bulk with it. The three 900 W towers and the 1000 W CyberPower weigh between 24.3 lb (11 kg) and 27.6 lb (12.5 kg) and stand 9.8 to 11.0 in tall. The CP850PFCLCD weighs 14.9 lb (6.76 kg) at 9.7 in tall. The BE850M2 weighs 9.04 lb (4.1 kg) and stands 5.47 in tall.

Runtime at the load you actually have

The full-load runtime on a spec sheet is the shortest figure the unit will ever deliver, and it describes a load this setup will not present. The published full-load figures here are 2 min at 900 W for the Eaton, 2.5 min at 1000 W for the CP1500PFCLCD, 3 min at 510 W for the CP850PFCLCD and 2 min at 100 percent load for the ABMT1000. None of those tells you what happens with a desktop, monitor, modem and router attached.

The useful figure is the one nearest your actual draw, and the units separate sharply here because not all of them publish one.

• CyberPower CP850PFCLCD: 9 min at half load, alongside the 3 min full-load figure.
• Amazon Basics ABMT1000: 9 min at 50 percent load, measured for ENERGY STAR certification rather than self-reported.
• Eaton 5S1500LCD: 13 min at 420 W. Eaton publishes runtime as a table in 60 W steps, so you can read the column nearest your own load instead of interpolating between two points. The 420 W column is the closest step to half load that this research recorded.
• CyberPower CP1500PFCLCD: 10 min at half load. A lower load runs longer, but CyberPower’s datasheet does not publish a figure at a lower step.
• APC BX1500M, BR1500MS2 and BE850M2: no runtime figure at any load appears in text in the APC datasheets retrieved for this guide.

The APC gap is why all three of its units score low on the runtime factor. The score reflects a figure you cannot check before buying, not a judgment about how long they run.

Waveform decides whether the desktop stays up

A UPS on battery generates its own AC output, and the manufacturers here describe that output in one of two ways. The CyberPower CP1500PFCLCD, CyberPower CP850PFCLCD and APC BR1500MS2 list sine wave output. The APC BX1500M and APC BE850M2 list a stepped approximation to a sinewave. Eaton’s technical specification and brochure do not state a waveform type. For the Amazon Basics ABMT1000, no manufacturer or certification document retrieved states one; the retail listing title describes “Sinewave Technology” without a specification entry.

The distinction matters because of the power supply inside the desktop. CyberPower’s product page for the CP850PFCLCD says the unit “safeguards mid- to high-end computer systems, servers and networking hardware that use conventional and Active Power Factor Correction (PFC) power supplies,” and its specification table lists “Active PFC Compatibility: Yes.” APC’s own FAQ on PFC power supplies and Back-UPS models says these units can take up to 8 ms to transfer to battery, long enough to momentarily remove power from a PFC supply and cause an inrush that can overload the UPS. APC does not state that its stepped-sine Back-UPS models are compatible with active-PFC supplies, and it directs anyone needing PFC compatibility to its Smart-UPS lines.

So by APC’s own account, the BX1500M and BE850M2 are the wrong choice for a desktop with an active-PFC power supply. The BR1500MS2’s datasheet lists sine wave output at the same 1500 VA rating as the BX1500M, but APC does not state active-PFC compatibility for it either. Within the stepped-wave pair, APC lists the BX1500M’s topology as line interactive and the BE850M2’s as standby. The Eaton and Amazon Basics units cannot be placed on either side of this line from their published documents, which is why both score low on the waveform factor despite the Eaton’s detailed runtime table.

Transfer time is the related number. CyberPower publishes 4 ms typical for both PFC Sinewave units. APC publishes 8 ms typical and 10 ms maximum for the BX1500M and BR1500MS2, and 6 ms typical with a 10 ms maximum for the BE850M2. No transfer time appears in the Eaton or Amazon Basics documents retrieved.

Count only the outlets that are on battery

Four devices need to stay up through an outage, so you need at least four battery-backed outlets. Total outlet count is a different and larger number on every unit here, and the surge-only outlets go dark the moment utility power does.

Two units also protect network lines. Both CyberPower units list RJ45 in/out protection rated for 10/100/1000 and PoE, and the CP1500PFCLCD adds RG6 coax in/out. If your modem’s coax line runs past the desk, that is a reason to prefer the larger CyberPower that has nothing to do with wattage.

The battery you will replace

A UPS battery is a consumable. APC publishes a 3 to 5 year design life for the BR1500MS2’s battery, and the unit outlives the cell only if you can swap it. Six of the seven manufacturers state the battery is user-replaceable, and most name a part:

• APC BX1500M: APCRBC124 cartridge
• APC BR1500MS2: APCRBC163 cartridge
• APC BE850M2: RBC17 cartridge
• CyberPower CP1500PFCLCD: RB1290X2 or RB1280X2B, depending on serial number prefix
• CyberPower CP850PFCLCD: RB1280A or RB1290, depending on serial number prefix
• Eaton 5S1500LCD: tool-less user-replaceable, not hot-swappable; no part number appears in the Eaton documents retrieved

The Amazon Basics ABMT1000 uses a 12 V / 9 Ah sealed lead-acid battery, and a third-party battery supplier lists compatible replacements for it. Amazon’s own listing and the ENERGY STAR filing do not state whether the owner is meant to replace it.

Recharge time matters for the second outage, because a unit still recharging has less than its full capacity available. CyberPower publishes 8 hours typical for both units and APC publishes 8 hours for the BE850M2. The two APC Pro towers, the BX1500M and BR1500MS2, publish 16 hours. Eaton and Amazon Basics publish no recharge time in the documents retrieved. Eaton does describe its ABM three-stage charging, which it states extends battery service life by 50 percent and gives advance warning of replacement; that is Eaton’s claim about its own technology, not an independently verified figure.

When 850 VA is enough, and when it is not

For a single desktop, monitor, modem and router, the CP850PFCLCD covers the decision on every factor that can be checked.

Step up to the CP1500PFCLCD when one of these applies. You intend to plug equipment into the battery outlets whose rated wattage approaches 510 W. You want the coax protection or the USB Type-A and Type-C charge ports, which the CP850PFCLCD lacks. You want more battery: the CP1500PFCLCD carries two 12 V / 9 Ah cells to the CP850PFCLCD’s one. Or you want the higher published surge rating and guarantee, 1445 J and $500,000 against 1150 J and $250,000. The trade is bulk: 24.9 lb (11.29 kg) and 14.0 in deep against 14.9 lb (6.76 kg) and 10.2 in deep.

The Amazon Basics ABMT1000 sits between them on watts at 550 W and is the only unit whose runtime was measured by a third party. It also carries the most gaps: no waveform specification beyond the retail listing title, no recharge time, no stated user-replaceable battery and no published equipment guarantee amount. If the desktop’s power supply uses active PFC, the waveform gap alone means the published record cannot confirm it fits.