Why Generator Sizing Matters

Selecting the right generator size is one of the most important decisions you'll make when investing in backup or prime power. An undersized generator won't handle your load, leading to equipment damage and unexpected shutdowns. An oversized unit wastes fuel, increases maintenance costs, and never operates at peak efficiency.

At ATOS Generators, we manufacture diesel power generator units ranging from 13 KVA to 3,000 KVA, powered by world-class engine brands including Baudouin, Perkins, Cummins, and Volvo. With this range, we can serve everything from small retail operations to large industrial facilities.

Understanding KVA vs. kW

Before sizing your generator, it's essential to understand the difference between KVA (Kilovolt-Amperes) and kW (Kilowatts):

KVA — Apparent power, which is the total power output of the generator
kW — Real power, the actual usable power after accounting for the power factor
Formula: kW = KVA × Power Factor (typically 0.8)

For example, a 500 KVA generator delivers approximately 400 kW of usable power. Always size your generator based on kW demand, then convert to KVA.

Step-by-Step Sizing Guide

Step 1: List All Equipment

Create a comprehensive list of every piece of equipment that will run on the generator. Include:

Motors and compressors (note starting vs. running watts)
HVAC systems
Lighting and office equipment
Specialized machinery
Safety and communication systems

Step 2: Calculate Total Load

Add up the running wattage of all equipment. For motors and compressors, multiply the running wattage by 3 to account for startup surge. This gives you the peak demand.

Step 3: Add a Safety Margin

Always add a 20-25% safety margin above your calculated peak demand. This accounts for:

Future expansion
Unexpected load increases
Optimal generator efficiency (generators perform best at 70-80% load)

Step 4: Consider Your Application

Different applications have different requirements:

Standby Power: For occasional use during outages — size to cover essential loads
Prime Power: For continuous operation in areas without grid power — size for full facility load with generous margin
Peak Shaving: To supplement grid power during high-demand periods — size based on the load you want to offset

Common Sizing Examples

Application	Typical Size Range
Small retail / office	20 – 100 KVA
Medium commercial building	100 – 500 KVA
Hospital / data center	500 – 1,500 KVA
Industrial / manufacturing	1,000 – 3,000 KVA
Construction site	100 – 1,000 KVA

Why Choose ATOS for Your Generator Needs?

With over 420 completed projects and 30+ years of experience, ATOS Generators provides:

Custom generator solutions designed to your exact specifications
Premium engines from Baudouin, Perkins, Cummins, and Volvo
Factory Acceptance Testing (FAT) per ISO-8528 standards
Comprehensive after-sales support and genuine spare parts
Synchronization panels for multi-generator setups when your needs grow

Don't guess on generator sizing. Contact our engineering team today for a free power assessment and custom quotation tailored to your facility's requirements.

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How to Choose the Right Generator Size for Your Business

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