E91 15 kVA vs Liebert EXS15KN
The Xtreme Power E91 15 kVA and the Liebert EXS15KN are online double-conversion UPS systems for 208/120V three-phase applications, both delivering full 15 kVA / 15 kW with internal VRLA batteries. The E91 delivers longer internal runtime at full load, a shorter cabinet height, and broader standard warranty and start-up coverage; the EXS15KN offers comparable efficiency and battery chemistry in a taller enclosure.
Where the E91 15 kVA leads
- Longer internal runtime at full load (11 vs 8 min @ 15 kW).
- A shorter cabinet height (40.2 vs 51.2 in).
- Full 15 kVA / 15 kW usable output.
- Equivalent high-efficiency operation.
- Broader standard warranty with start-up included.
15 kVA three-phase UPS, side by side
| Specification | Xtreme Power E91 15 kVA | Vertiv Liebert EXS15KN | Advantage |
|---|---|---|---|
| Rated capacity | 15 kVA / 15 kW | 15 kVA / 15 kW | Equal usable power |
| Voltage | 208/120V, 3-phase | 208/120V, 3-phase | Direct electrical match |
| UPS topology | Online double-conversion | Online double-conversion | Equivalent protection |
| Battery architecture | Internal VRLA batteries | Internal VRLA batteries | Equivalent chemistry |
| Internal runtime (full load) | 11 min @ 15 kW | 8 min @ 15 kW | Longer standard runtime |
| Efficiency (online / ECO) | Up to 94% / 98% | Up to 94% / 99% | Comparable; EXS 99% ECO |
| Dimensions (W × D × H) | 11.9 × 34 × 40.2 in | 13 × 25.6 × 51.2 in | Shorter cabinet |
| Output distribution | Optional receptacles | Optional receptacles | Equivalent flexibility |
| Warranty & start-up | 2-year + start-up included | 1-year standard | Broader coverage |
| TAA compliance | TAA compliant | TAA available | Eligible for federal procurement |
Both are true online double-conversion three-phase UPS with full 15 kW usable output and internal VRLA batteries. The E91 leads on full-load runtime (11 vs 8 min), a shorter cabinet, and broader warranty with start-up; the EXS posts a marginally higher ECO figure (99 vs 98%). Confirm Liebert EXS specifications against current Vertiv documentation.
Choosing between them
Choose the E91 for longer full-load runtime, a shorter cabinet, and broader warranty with start-up; the EXS15KN fits where an existing Vertiv standard governs.
Choose the E91 15 kVA if you need
- Longer runtime at full rated load
- A shorter cabinet height
- Full 15 kW usable capacity
- Integrated start-up coverage
- Longer standard warranty
The Liebert EXS15KN may fit if you need
- Facilities standardized on Vertiv infrastructure
- Alignment with existing EXS deployments
- Vertiv 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.