A 200 kW critical load, sized to a standard UPS frame with full N+1 redundancy — plus how much battery energy a 15-minute ride-through actually needs.
| Critical load | 200 kW at 0.9 power factor |
| Design margin | 20% |
| Redundancy | 2 UPS frames, N+1 (either one can carry the full load alone) |
| UPS rated output PF | 0.9 |
| Required backup time | 15 minutes |
| Battery depth of discharge / inverter efficiency | 80% / 92% |
| DC bus voltage | 480 V |
With 2 frames installed and N+1 redundancy, either frame alone must carry the full margined load.
| Check | Requirement | Actual | Status |
|---|---|---|---|
| Recommended UPS frame size | n/a (this is the sizing result) | 300 kVA (270 kW) per frame, 2 frames installed | ✓ PASS |
| Battery nameplate energy | n/a (this is the sizing result) | 67.9 kWh (≈141.5 Ah at 480 V) | ✓ PASS |
Key insight: Depth of discharge and inverter efficiency both shrink usable energy relative to nameplate battery capacity — a battery can't be discharged to 0% DoD without damage, and DC-to-AC conversion isn't lossless, so the nameplate battery has to be meaningfully larger (67.9 kWh here) than the 50 kWh the load actually needs, purely to account for those two real-world losses.
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Open UPS Sizing calculator →N+1 specifically means N units are needed to carry the load, plus 1 spare — with N=1 required unit and 1 spare (2 total installed), each individual frame has to be sized for the full margined load, since either one must be able to run the entire critical load alone if the other fails or is taken down for maintenance. This is the same underlying principle as the N-1 redundancy convention used in the Transformer Sizer calculator, just phrased from the opposite direction (N+1 installed vs. N-1 surviving).
No — this is explicitly a quick sizing estimate (usable energy = load x time, then correcting for DoD and efficiency), not a full IEEE 485 duty-cycle section-by-section design. For a final battery specification, especially one with a varying load profile rather than one constant load for the whole backup period, the dedicated Battery & DC System Sizing calculator's full method should be used instead.