E91 vs Eaton 9355
The Xtreme Power E91 Series and the Eaton 9355 are three-phase online double-conversion UPS platforms for 208/120V applications. Both deliver premium double-conversion protection with integrated maintenance bypass; they differ most in usable real-power output, operating efficiency, physical footprint and weight, and standard ownership coverage. The E91 delivers full usable kW at unity power factor, higher efficiency, and a significantly smaller, lighter installation, with factory start-up and a longer standard warranty. The 9355 provides comparable topology and longer raw internal runtime, but at reduced 0.9-PF usable output and in a larger, heavier chassis. The E91 spans 10–40 kVA; direct 9355 comparisons are provided at 10–30 kVA.
Where the E91 leads
- Full usable kW at unity power factor (1.0) — vs the 9355’s 0.9 PF, which derates usable watts from the same kVA.
- Higher operating efficiency (up to ~94% vs ~91% online), reducing energy and cooling load.
- A significantly smaller and lighter installation — the 9355 reaches substantially higher weights at matched capacity.
- Factory start-up included as standard, plus a longer standard electronics warranty.
- Defined runtime at full rated load, with external battery cabinets for expansion.
Compact three-phase UPS platforms, side by side
| Specification | Xtreme Power E91 Series | Eaton 9355 | Advantage |
|---|---|---|---|
| Usable output (power factor) | Full kW at unity PF (1.0) | Reduced kW at 0.9 PF | More usable watts from the same kVA |
| UPS topology | Online double-conversion | Online double-conversion | Comparable premium protection |
| Operating efficiency | Up to ~94% online | ~91% online | Lower energy & cooling load |
| Maintenance bypass | Standard (integrated) | Standard (integrated) | Both integrated |
| Footprint | Compact integrated cabinet | Larger chassis | Smaller, denser installation |
| System weight | Significantly lower | Substantially higher (up to ~1,160 lb) | Lower floor loading, easier logistics |
| Internal runtime | Defined at full rated load | Longer raw minutes, larger/heavier cabinet | Eaton longer, but at lower load & far heavier |
| Runtime scalability | External battery cabinets | External battery cabinets | Comparable scalability |
| Warranty (electronics) | 2 years standard | 1-year parts | Longer standard coverage |
| Start-up & labor | Factory start-up included | Start-up optional; 90-day labor | More comprehensive standard coverage |
| TAA compliance | TAA compliant | TAA compliant | Both eligible for federal procurement |
Both are true online double-conversion three-phase UPS with integrated bypass and TAA eligibility. The E91 leads on usable unity-PF capacity, efficiency, footprint, weight, factory start-up, and standard warranty across the line; the 9355 posts longer raw internal runtime, but at reduced 0.9-PF output and substantially higher size and weight. Specifications are based on publicly available manufacturer documentation; confirm current Eaton 9355 figures against Eaton documentation, and see the per-capacity pages for model-specific specs.
Choosing between them
Both deliver premium online protection, so the decision turns on usable capacity, efficiency, installation footprint, and ownership. Choose the E91 for full unity-PF usable kW, higher efficiency, a smaller and lighter cabinet, factory start-up, and a longer warranty; the 9355 fits where longer base-cabinet runtime is the priority and a larger, heavier enclosure is acceptable, or where an existing Eaton standard governs.
Choose the E91 Series if you need
- Full usable kW at unity power factor
- Higher operating efficiency
- A smaller, lighter installation
- Defined runtime at full rated load
- Factory start-up included as standard
- A longer standard electronics warranty
- TAA-compliant procurement
The 9355 may fit if you need
- An existing Eaton standard governs the facility
- Longer base-cabinet internal runtime is the priority
- A larger, heavier enclosure is acceptable
- Eaton service ecosystem continuity
Related comparisons
Standardizing compact three-phase UPS across your facilities?
Xtreme Power supports E91 three-phase UPS sizing, runtime planning with external battery cabinets, modernization strategy for legacy three-phase UPS, and TAA-compliant procurement for healthcare, education, retail, industrial, and enterprise infrastructure.