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DATA CENTER POWER & COOLING

UPS Capacity & Battery Backup Runtime Calculator

Plan UPS capacity and battery autonomy from critical load, redundancy and real battery derating assumptions.

UPS capacityBattery bankRuntimeLoad margin
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Engineering inputs

Set the engineering assumptions and design parameters.

UPS load, redundancy & battery

Battery autonomy model

Battery runtime is an engineering estimate. Final autonomy must be checked against the exact UPS/battery manufacturer discharge curve.

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Engineering results

Review calculated capacity, limits and design checks.

Engineering results

Required UPS capacity
Recommended modules
UPS utilization
1 module failed
Estimated runtime
Required battery
Usable battery energy
Estimated bypass current

What this tool checks

UPS kW/kVA capacity, modular N/N+1/N+2 sizing, one-module failure headroom, energy-based battery autonomy, target-runtime battery sizing, recharge planning and bypass current estimation.

Engineering boundary

Battery discharge is nonlinear in real systems. Use this result for planning and compare it with the exact manufacturer runtime chart, battery cabinet configuration, end-of-discharge voltage, ambient temperature and site electrical protection design.

FAQ and references

Why size both kW and kVA?

UPS output has both real-power and apparent-power limits. The selected system must satisfy both.

Why add headroom?

Headroom allows for load growth, transients and avoiding continuous operation near the UPS limit.

Is battery runtime linear with Ah?

This calculator provides an energy-based planning estimate. Real runtime depends on battery chemistry, discharge rate, voltage cut-off, age, temperature and the manufacturer runtime curve.

What does N+1 mean here?

The active UPS modules required for the design load are calculated first, then one extra module is added. The one-module-failed state is checked separately.

Can this replace a vendor UPS selector?

No. Use the manufacturer runtime curve, battery cabinet limits, bypass rating, fault-current data and site electrical rules before final selection.

Engineering references

Schneider Electric — UPS sizing and load considerations · APC UPS Selector

Content reviewed: 2026-09-10

ENGINEERING WORKFLOW

Continue the engineering workflow

Current workflowData Center Critical Power & Cooling Workflow

Move from rack load through UPS protection, generator/ATS ride-through, precision cooling, airflow containment and facility PUE as one critical-infrastructure planning sequence.

Step 2 of 6
PreviousNetwork Rack Power & Cooling CalculatorCalculate rack power, current, cooling load, energy and cost.NextGenerator + UPS Transfer & Ride-Through PlannerPlan UPS ride-through, generator start/retry timing, ATS transfer, redundancy and critical-load continuity after utility failure.

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