Buying & comparison
UPS for a NAS: APC vs CyberPower vs EcoFlow
A source-backed guide to choosing a UPS for a NAS or home server — why an Active-PFC PSU needs a pure sine wave, line-interactive vs online, and auto-shutdown.
Who this is for
A NAS without a UPS is one brownout away from a corrupt pool or an interrupted write. But the wrong UPS is almost as bad: most modern NAS and PC power supplies use Active PFC, and a cheap stepped-sine UPS can make them shut down at the moment of transfer. This guide compares the three things a home operator actually picks between, with the spec that matters most — output waveform — front and center. Size the runtime for your real load with the UPS runtime estimator, and start with what a UPS is and whether you need one.
Bottom line
For an Active-PFC NAS, the rule is simple: buy a pure sine wave UPS. A line-interactive pure-sine unit — CyberPower CP1500PFCLCD (best value, more usable watts) or APC Back-UPS Pro BR1500MS2 (ecosystem, 3-year warranty) — is the home sweet spot, and both shut your NAS down cleanly over USB. Online double-conversion is overkill for most homes. An EcoFlow DELTA 2 gives hours of runtime and LiFePO4 longevity, but it's an EPS with a slower switchover and no native NAS auto-shutdown — great for long backup, weaker as an automatic guardian.
How to choose
- Pure sine wave (for Active PFC) — the #1 rule
- Most NAS/PC power supplies use Active PFC. On a stepped/simulated-sine UPS, the zero-output gap during the switch to battery can make an Active-PFC supply shut down or fail to transfer. Buy a pure/true sine wave UPS for a NAS — not a cheap stepped-sine model.
- Topology: line-interactive is the home sweet spot
- Line-interactive with AVR (the APC Back-UPS Pro and CyberPower PFC lines) transfers fast enough (~6–10 ms) for Active-PFC gear and is far cheaper than online double-conversion, which gives zero transfer but is overkill for most homes.
- Watts vs VA, and runtime
- The watt rating (not the VA number) is the real ceiling for your load, and runtime depends on how much of that you draw — size it with the UPS runtime estimator rather than trusting a headline minute figure.
- Auto-shutdown integration
- For a NAS, the UPS should trigger a graceful shutdown before the battery dies. APC (PowerChute) and CyberPower (PowerPanel) units do this over USB and are supported by Network UPS Tools (NUT) on Synology, TrueNAS, and Unraid. A portable power station typically has no such daemon.
- Battery chemistry and life
- Desktop UPSes use sealed lead-acid (SLA) batteries with a ~3–5 year service life; budget for a replacement. LiFePO4 power stations (EcoFlow) last thousands of cycles (~10 years) but trade that for the EPS switchover caveat.
The options
Runtime figures depend entirely on your load, so they aren't compared here — size yours with the runtime estimator. The decisive spec is the output waveform.
APC Back-UPS Pro BR1500MS2
APC (Schneider Electric)A line-interactive, true-sine-wave UPS with AVR — the mainstream home/NAS pick when you want a real UPS with replaceable batteries, clean transfer, and the APC/PowerChute ecosystem.
Best for
A NAS, desktop, or small server with an Active-PFC supply where you want true sine wave, USB auto-shutdown via PowerChute/NUT, user-replaceable batteries, and a 3-year warranty.
Watch-outs
Sealed lead-acid (~3–5 year life, long recharge). It's the 'Pro'/MS2 line that's true sine — the cheaper APC Back-UPS (BE/BN) models are stepped/simulated and should be avoided for an Active-PFC NAS. Line-interactive still has a brief transfer (not zero); for zero-transfer you'd step up to Smart-UPS On-Line.
| Spec | Value | Verification |
|---|---|---|
| Topology | Line-interactive with Automatic Voltage Regulation (AVR). | Manufacturer-confirmedsource |
| Output waveform | True/pure sine wave on battery; ~8 ms typical / 10 ms max transfer. (The cheaper BE/BN APC models are stepped sine — avoid those for Active-PFC gear.) | Manufacturer-confirmedsource |
| Why pure sine matters | An Active-PFC NAS/PC supply can shut down on a stepped sine wave's transfer gap; a pure sine wave is continuous and avoids it. | Researchedsource |
| Rating | 1500 VA / 900 W — the 900 W figure is the real load ceiling; runtime depends on your draw (size it with the estimator). | Manufacturer-confirmedsource |
| Battery | Sealed lead-acid, user-replaceable; ~3–5 year design life, ~16 h recharge; 6 battery-backup + 4 surge-only outlets, LCD. | Manufacturer-confirmedsource |
| NAS auto-shutdown | USB auto-shutdown via APC PowerChute and NUT — supported by Synology DSM, TrueNAS, and Unraid (NUT plugin). | Manufacturer-confirmedsource |
CyberPower CP1500PFCLCD
CyberPowerA line-interactive pure-sine-wave UPS explicitly built and marketed as Active-PFC compatible — the value pure-sine pick for a NAS or PC, with more usable watts than the comparable APC.
Best for
Anyone who wants pure sine wave and Active-PFC compatibility at the friendliest price, with 1000 W of usable power, a color LCD, and free PowerPanel software (or NUT) for graceful shutdown.
Watch-outs
Sealed lead-acid (the usual ~3–5 year replacement cadence). Line-interactive, so there's still a small transfer to battery (not a zero-transfer online unit). Confirm the current revision ('a' suffix) at purchase.
| Spec | Value | Verification |
|---|---|---|
| Topology | Line-interactive with AVR (GreenPower energy-saving design). | Manufacturer-confirmedsource |
| Output waveform | Pure sine wave; explicitly marketed as 'Active PFC Compatible'. | Manufacturer-confirmedsource |
| Why pure sine matters | CyberPower notes a simulated sine wave's zero-output gap can crash Active-PFC PSUs at the switch to battery; pure sine is continuous output. | Manufacturer-confirmedsource |
| Rating | 1500 VA / 1000 W — more usable watts than the comparable APC; runtime depends on load (size it with the estimator). | Manufacturer-confirmedsource |
| Outlets & LCD | 12 NEMA 5-15R outlets split into battery+surge and surge-only banks, plus a tiltable color LCD. | Manufacturer-confirmedsource |
| NAS auto-shutdown | Free PowerPanel software (Windows/Linux/macOS) for USB auto-shutdown; also widely supported by NUT on Synology/TrueNAS/Unraid. | Manufacturer-confirmedsource |
EcoFlow DELTA 2
EcoFlowA LiFePO4 portable power station with an EPS pass-through mode — far longer runtime and battery life than a desktop UPS, but an EPS rather than a true zero-transfer UPS.
Best for
Operators who want one box that doubles as long-duration backup (hours for a router + NAS), recharges fast, lasts thousands of cycles, and can go portable/off-grid — whose gear tolerates the EPS switchover.
Watch-outs
It's EPS pass-through, not online: switchover is slower and less defined than a line-interactive UPS — borderline for sensitive Active-PFC gear. And it has no native NUT/Synology/TrueNAS USB integration, so a NAS won't shut down automatically the way it does with APC/CyberPower.
| Spec | Value | Verification |
|---|---|---|
| Topology / mode | EPS (emergency power supply) pass-through — auto-switches to battery when the grid drops; not a true online/zero-transfer UPS. | Manufacturer-confirmedsource |
| Battery chemistry & life | LiFePO4 (LFP), 3000+ cycles to 80%+ capacity (~10 years), 5-year warranty — far beyond sealed lead-acid. | Manufacturer-confirmedsource |
| Capacity & output | 1024 Wh capacity, 1800 W AC output (up to 2200 W with X-Boost), expandable — hours of runtime rather than minutes. | Manufacturer-confirmedsource |
| Switchover caveat | EPS switchover is community-reported around ~30 ms (some low-power loads slower) — slower than a line-interactive UPS (~6–10 ms), so it's borderline for sensitive Active-PFC gear. | User-reportedsource |
| Recharge speed | 0–80% in ~50 minutes via fast AC charging, plus up to 500 W solar — versus the ~16 h recharge of a typical SLA UPS. | Manufacturer-confirmedsource |
| NAS auto-shutdown | No native NUT/Synology/TrueNAS USB daemon — monitoring is via the EcoFlow app, so it does not trigger an automatic graceful NAS shutdown. | Researchedsource |
Pick by use case
A NAS that must shut down gracefully, and you want the established ecosystem and a 3-year warranty
→ APC Back-UPS Pro BR1500MS2. True sine wave, line-interactive, USB auto-shutdown via PowerChute/NUT, and APC's support footprint — a safe default for an Active-PFC NAS.
The best-value pure-sine UPS with more usable watts for the money
→ CyberPower CP1500PFCLCD. Pure sine, explicitly Active-PFC compatible, 1000 W (vs the APC's 900 W), and free PowerPanel — the value pick that still shuts a NAS down cleanly.
You want hours of runtime, LiFePO4 longevity, and portability, and your gear tolerates an EPS
→ EcoFlow DELTA 2. Far more capacity and battery cycles than a desktop UPS, with fast recharge and solar input — accepting the EPS switchover and the lack of automatic NAS shutdown.
The cheapest correct protection for an Active-PFC NAS
→ CyberPower CP1500PFCLCD. It hits the one non-negotiable (pure sine wave for Active PFC) at the lowest cost while still doing graceful USB shutdown.
Run the numbers
Turn the decision into a calculation before you buy — size the capacity, the backup, and the UPS for your exact setup.
Related runbooks
How we verified this guide
2026-06-17 · Reviewed by HomeTechOps. Verified against APC/Schneider Electric, CyberPower, and EcoFlow official product pages plus NUT, Synology, and TrueNAS docs on 2026-06-17. The Active-PFC pure-sine-wave rule is sourced to CyberPower and APC; the EcoFlow EPS switchover (~30 ms) is community-reported and labeled as such, not a first-party UPS spec. Runtime depends on load — size it with the estimator. No prices are listed; we link out.
Source-backed checks
HomeTechOps turns official docs and conservative safety rules into a shorter runbook. These links are the source trail for the page direction.