H‑Infinity

An undersized UPS means critical loads lose power when you need them most. An oversized UPS wastes capital and operates inefficiently. Our UPS sizing study calculates the exact kVA and kWh requirements for your critical load profile, recommends the optimal topology (standby, line-interactive, double-conversion), and specifies battery bank capacity for your required backup duration.

01What is UPS Sizing?

UPS sizing goes beyond adding up the connected load. It involves a detailed analysis of:

Load Profiling

Identify all critical loads, classify them by importance, measure or estimate their active (kW) and apparent (kVA) power demands, and account for diversity and simultaneity factors.

Power Factor

Different loads have different power factors. The UPS must be sized for apparent power (kVA), not just real power (kW).

Harmonic Content

Non-linear loads (VFDs, SMPS) generate harmonics that increase UPS thermal stress. K-factor and derating calculations are essential.

Future Expansion

Account for planned load growth, N+1 redundancy requirements, and modularity for phased capacity expansion.

02Why Proper UPS Sizing Matters

The consequences of improper UPS sizing are costly and potentially catastrophic:

▸Data Centre Outages — An undersized UPS during a grid failure can cause server shutdowns, data loss, and business disruption costing millions per hour.
▸Medical Equipment Failure — Hospitals rely on UPS for life-critical equipment. Sizing must account for all ICU, OR, and lab loads with full redundancy.
▸Wasted Capital — Oversized UPS systems waste 20–40% of capital expenditure and operate at poor efficiency (60–70% load) increasing energy costs.
▸Battery Underestimation — Incorrect battery sizing means backup time is shorter than specified, leaving critical loads unprotected when needed most.

03Our Approach

Our UPS sizing methodology follows a systematic engineering approach:

1. Load Survey & Classification

Categorise loads by criticality (Tier I–IV per TIA-942 or EN 50173), determine individual kW/kVA demands, and apply diversity factors.

2. UPS Topology Selection

Recommend optimal topology: double-conversion online for Tier III/IV, line- interactive for Tier I/II, considering efficiency, transfer time, and fault ride- through requirements.

3. Battery Sizing Calculation

Calculate battery Ah capacity for required backup time (typically 15 min to 8 hours), accounting for end-of-life derating, temperature compensation, and voltage drop in cables.

4. Redundancy Analysis

Evaluate N, N+1, 2N, or 2N+1 redundancy architectures based on load criticality and availability requirements.

04Scope of UPS Sizing

Our comprehensive UPS sizing studies include:

▸Critical Load Schedule — Detailed list of all critical loads with kW, kVA, PF, and phase requirements.
▸UPS Capacity Sizing — kVA rating with 20–25% future expansion margin.
▸Battery Bank Design — Number of batteries, series/parallel configuration, Ah rating, and estimated weight/footprint.
▸Single Line Diagram — UPS system SL D showing input distribution, UPS, batteries, and critical load panels.

05Standards & Compliance

✓IEC 62040 — UPS Requirements

✓EN 50173 — IT Infrastructure cabling

✓TIA-942 — Telecom Infrastructure Standard

✓IEEE 485 — Pb-A Battery Sizing

06Why H-Infinity

We've sized UPS systems for data centres, hospitals, telecom exchanges, and industrial control systems — from 10 kVA rack-mounted units to 2 MW three-phase installations. Our studies consider total cost of ownership including efficiency, maintainability, and expandability, not just upfront capital cost.

UPS Sizing