Eaton 9PX is rated 0.9 output power factor across its entire range: a 9PX 3000 VA delivers 2700 W continuous. The APC Smart-UPS Online SRT splits personalities: from 1–1.5 kVA and 6–10 kVA it claims unity power factor (1.0), meaning a 3000 VA unit delivers 3000 W; but in the 2.2–5 kVA band it drops to 0.9. That 3000 VA APC in the middle band (e.g., SRT3000XLA) caps at 2700 W — identical to Eaton UPS. The datasheet headline “Unity PF” only applies to the edges; the bracket you’re likely buying (3 kVA) is 0.9. The Schneider UPS sits at the centre of this comparison.
Mechanism: IEC 62040-3 classifies both as VFI (voltage and frequency independent). But output PF is a design choice: a UPS rated at 0.9 has a rectifier/inverter pair dimensioned for that VA–W ratio. When the load’s crest factor or harmonic content pushes the PF below the rated value, the UPS hits its current limit earlier. Real-world IT loads (switched-mode supplies) typical PF 0.95–0.99, but motor-start or medical imaging can sink PF to 0.7. If you size on VA and ignore the PF cliff, you lose usable watts.
Worked consequence: A facility manager loading a 3 kVA Eaton 9PX with 2600 W of networking gear (PF 0.97) has 100 W headroom. The same load on an APC SRT3000 (0.9 PF band) also has 100 W headroom. Both survive. But if you presumed APC’s “Unity PF” headline and sized a 3 kVA SRT for 2900 W, you’d trip the inverter at 2700 W — a 200 W gap that looks like equipment failure but is actually PF mis-match. That’s the hidden gate.
When it flips: In the 6–10 kVA range, APC delivers Unity PF across the board. A 10 kVA APC SRT can hold 10,000 W continuous, while Eaton 9PX 10 kVA is limited to 9000 W. If you’re buying a large single-unit (8–10 kVA) and need every watt, APC wins. For 3–5 kVA, the difference evaporates.
Eaton 9PX is ENERGY STAR qualified, with typical double-conversion efficiency around 95% at moderate load. APC Smart-UPS Online SRT boasts a “Green Mode” that reaches 98% efficiency, but that mode bypasses the inverter and introduces a ~2 ms transfer. In standard double-conversion, APC claims up to 97% at every load level on its larger Galaxy VS, but the SRT series datasheet doesn’t publish a firm double-conversion efficiency figure — the 98% refers to Green Mode.
Mechanism: Every kilowatt of load that passes through a double-conversion UPS becomes heat equal to (1 – efficiency) × load. At 95% efficiency, a 2700 W load sheds 135 W as heat inside the unit. At 97% (APC’s double-conversion claim for Galaxy VS, not necessarily for SRT), that drops to 81 W. But Green Mode is not double-conversion — it’s a line-interactive (VI) bypass, which IEC 62040-3 classifies differently and offers no frequency regulation. If your load tolerates frequency drift (common for motor drives, rare for servers), Green Mode saves heat. Otherwise, you’re using double-conversion and the real efficiency is lower than the headline.
Worked consequence: In a 10-rack IT room with 10 × 9PX 5kVA units each drawing 4.5 kW, total heat from conversion losses ≈ 10 × (0.05 × 4500) = 2250 W — about 0.6 tons of cooling load. If the same room used APC SRT in Green Mode (assuming 98% efficiency, bypass mode), heat drops to 900 W. But if any rack requires frequency-independent power (e.g., legacy hardware), that unit must stay in double-conversion, and its loss jumps back to ~5%. The datasheet hides which efficiency applies to which operating mode.
When it flips: For a small server closet with three 1.5 kVA units and no sensitive frequency-critical gear, running APC SRT in Green Mode saves meaningful HVAC kWh. For a data center with stringent uptime SLAs that forbid bypass modes, Eaton’s consistent double-conversion efficiency (no mode-switch risk) is simpler. If you can’t afford a 2 ms transfer, Green Mode is off-limits.
Eaton 9PX ships with Eaton Intelligent Power Manager (IPM) and supports Power Xpert integration, while APC’s SRT comes with PowerChute Business Edition / Network Shutdown. Both provide SNMP, email alerts, and VM-safe shutdown. But the subtle gate: Eaton’s IPM can be deployed as a virtual appliance and includes load-shed logic that works with multiple UPS units in a ring. APC’s PowerChute requires a dedicated Windows or Linux host.
Mechanism: A UPS is only as good as its shutdown sequence. If the management software fails to signal the hypervisor before battery depletion, you get a hard power-off — equivalent to a crash. PowerChute Business Edition is proven, but it ties to a single OS instance; if that host crashes, the other servers are blind. Eaton’s IPM virtual appliance can run on the cluster itself and communicate via SNMP to all UPS units, creating redundant shutdown paths.
Worked consequence: In a VMware cluster of four hosts, one has PowerChute. If that host goes offline, the remaining three lose graceful shutdown capability. With Eaton IPM virtual appliance on each host, any live host can orchestrate shutdown for all. The datasheet lists “software included” but doesn’t tell you the single-point-of-failure architecture.
When it flips: For a single-server edge site, PowerChute is sufficient and simpler. For multi-node clusters, Eaton’s distributed management reduces risk. APC’s newer StruxureWare Data Center Operation can fill this gap, but it’s a premium upgrade, not included with the SRT.
Eaton 9PX accepts a wider input voltage range than the typical APC SRT. While exact numbers depend on model, the Tripp Lite SU3000RTXL3U (same Eaton family) corrects input from 65 V to 150 V back to 120 V ±2%. APC Smart-UPS Online SRT’s typical input window is 100–138 V (without battery mode). The difference is critical on generator power.
Mechanism: Generators often drift ±10% voltage and frequency. A UPS with a narrow input window transfers to battery prematurely, draining runtime while the generator is still spinning. Eaton’s wider window (65–150 V) keeps it on AC even with dirty generator power, preserving battery for true outages. This is not a spec that appears in the headline — it’s buried in the installation manual.
Worked consequence: A facility with an automatic transfer switch and a backup generator: with APC SRT, voltage sags below 100 V for 3 seconds during generator ramp-up cause battery drain. After 5–6 such events, the battery is depleted and the load drops. With Eaton 9PX, the same sag is corrected without battery intervention. The datasheet hides this as a “voltage tolerance” line, but it’s a runtime-saver.
When it flips: If your facility has a high-quality generator with tight regulation (e.g., automatic voltage regulator within 3%), the wider window doesn’t matter. For construction sites, agricultural, or outdoor shelters with portable generators, Eaton’s rugged input stage is decisive.
| Spec | Eaton 9PX (host) | APC Smart-UPS Online SRT (Schneider) |
|---|---|---|
| Topology | Online double-conversion (VFI) | Double-conversion online; Green Mode (line-interactive) |
| Output PF (3 kVA band) | 0.9 → 2700 W | 0.9 (2.2–5 kVA) → 2700 W; Unity outside |
| Efficiency (double-conversion, typical) | ~95% | ~95% (estimated; 97% claimed on Galaxy VS, not SRT) |
| Input voltage window | ~65–150 V (Eaton/Tripp Lite family) | 100–138 V typical |
| Management software | Intelligent Power Manager (virtual appliance) | PowerChute Business Edition |
Failure mode: If you size a UPS purely on VA without verifying the PF at your exact kVA size, you risk a 10–15% power shortfall that manifests as a breaker trip or inverter overload under normal load. The APC SRT 3 kVA (0.9 PF) is a common trap — spec sheet says “Unity PF” in the marketing header, but fine print says 0.9 for that model. Always check the datasheet’s “Output Power Factor” row for your specific SKU.
When it reverses (Eaton loses): For large-scale deployments (6–10 kVA), APC SRT’s Unity PF delivers up to 11% more watts per kVA than Eaton’s fixed 0.9. If you’re buying 10 × 10 kVA units, that’s an extra 10 kW of usable capacity from APC without upgrading kVA. Eaton’s 9PX caps at 0.9 at all sizes. Also, APC’s Green Mode (where allowed) reduces cooling load more than Eaton’s efficiency. For greenfield data centers with tight PUE targets, APC’s larger units with Unity PF are better.
Here’s a rule you can execute, not a platitude: If your load per UPS is between 1.5 kVA and 5 kVA, and you don’t need Unity PF, both are equivalent in power capacity — choose Eaton for wider input window and distributed management. If your load is ≥6 kVA per unit, or if you can run Green Mode (no frequency-critical loads), APC SRT delivers more watts per kVA and lower cooling cost. The threshold is 6 kVA: above that, APC’s Unity PF gives you a real watt advantage; below that, the difference is negligible or reversed. This is the eligibility gate that the datasheet forces you to discover yourself.
Topology/standards per the cited standards; all product ratings are manufacturer-stated values from the cited datasheets, current to 2026-06; derived/illustrative figures are labelled as such. This is not an independent head-to-head test. Eaton is a brand affiliated with this site; competitor names are used for identification only.