M90S-4S vs Eaton 9PXM8S8K
The Xtreme Power M90S-4S and Eaton 9PXM8S8K are single-phase modular online double-conversion UPS for IT, network, and edge infrastructure. Both are modular and scalable; the M90S-4S is configured to a higher rating (12 kW at unity power factor) than the 9PXM8S8K (7.2 kW at 0.9 PF), so it delivers more usable watts and longer baseline runtime. Size to your actual load when comparing.
What the M90S-4S brings
- Covers the 9PXM8S8K 7.2 kW load with headroom, at unity power factor (12 kW vs 7.2 kW)
- Longer baseline internal runtime before adding battery modules
- Integrated maintenance bypass as standard (optional or external on the Eaton)
- Chassis plus module-level diagnostics for faster service
- Longer standard warranty (3 years vs 2)
Side-by-side specifications
| Specification | Xtreme Power M90S-4S | Eaton 9PXM8S8K | Advantage / consideration |
|---|---|---|---|
| Usable power | 12 kVA / 12 kW (unity PF) | 8 kVA / 7.2 kW (0.9 PF) | M90S covers the load with headroom (also a higher-rated unit) |
| Topology | Online double conversion | Online double conversion | Equivalent protection |
| Scalability ceiling | Up to 12 kVA (4-slot chassis) | 8 kVA, scalable to 16 kVA | 9PXM8S8K scales higher (to 16 kVA); step to the M90S-6S for more headroom |
| Internal runtime (full load) | Approx. 9 min @ 12 kW | Approx. 6 min @ 7.2 kW (base) | M90S – longer baseline runtime |
| Maintenance bypass | Standard, integrated | Optional / external | M90S – integrated bypass |
| Rack / tower mounting | Rack kit (M90S-RMK) or tower | Rack / tower convertible | Both rack and tower capable |
| Display & diagnostics | Chassis LCD + module-level displays | Single chassis LCD | M90S – module-level visibility |
| Certifications | UL, cUL, TAA | UL, cUL, TAA | Both TAA compliant |
| Warranty | 3 years (electronics & batteries) | 2-year limited | M90S – longer coverage |
Specifications based on publicly available manufacturer documentation; confirm against current vendor data. The M90S-4S is configured to a higher rating (12 kW) than the 9PXM8S8K (7.2 kW), so several advantages reflect the larger size as well as the unity-power-factor design. Match the configuration to your actual load.
Choosing between them
Both are single-phase modular online UPS. The M90S-4S leads on usable kW (unity PF), baseline runtime, integrated bypass, module-level diagnostics, and warranty. The 9PXM8S8K is a lower-density, Eaton-standardized option. Because the M90S-4S is rated higher, size both to your real load before comparing.
Choose the M90S-4S if you need
- Up to 12 kW usable output (unity PF) from a modular chassis
- More power headroom without oversizing kVA
- Integrated maintenance bypass as standard
- Module-level diagnostics for faster service
- A longer (3-year) standard warranty
The Eaton 9PXM8S8K may fit if you need
- Alignment with an existing Eaton 9PXM platform
- A lower-density configuration around 7 kW usable
- Modular expansion within the Eaton ecosystem
Frequently asked questions
No. The M90S-4S is configured to 12 kVA / 12 kW (unity power factor), while the 9PXM8S8K base is 8 kVA / 7.2 kW (0.9 PF). The M90S-4S delivers more usable watts and longer runtime, but it is also a higher-rated unit, so size both to your actual load.
Two reasons: the M90S-4S is rated to a higher capacity, and it runs at unity power factor (1.0), so kVA equals kW. The 9PXM8S8K runs at 0.9 PF, so its 8 kVA yields 7.2 kW.
Yes. The 9PXM8S8K is 8 kVA scalable to 16 kVA in its 8-slot chassis, while the M90S-4S tops out at 12 kVA. For loads at or near the 9PXM8S8K 7.2 kW rating, the M90S-4S is the closest-fitting match with headroom; for loads that will grow past 12 kVA, use the M90S-6S, which scales to 24 kVA.
Yes. Maintenance bypass is standard and integrated on the M90S-4S, which lowers installation cost and saves space; on the 9PXM8S8K it is optional or external.
Yes. The M90S-4S is UL, cUL, and TAA compliant, making it eligible for federal and regulated-market procurement. The 9PXM8S8K is also TAA compliant.
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