How to Choose the Right Generator Size: A Practical Step-by-Step Guide
Nama Jeddah Team • January 25, 2026
Choosing the wrong generator size can be costly: too small means outages and breakdowns, too large means wasted fuel and money. In this practical guide, we walk you through step by step how to calculate your needs and select the perfect generator.
Step 1: List All Electrical Loads
Start by creating a comprehensive list of every device and piece of equipment the generator will power. For each item, note:
- Wattage (W): Usually printed on the data plate or in the user manual.
- Starting current: Some devices like AC units and motors need 2–3x their normal current at startup.
- Operating hours: Does the device run continuously or intermittently?
Step 2: Calculate Total Load
Add up the wattage of all devices running simultaneously. Practical example:
| Equipment | Qty | Watts Each | Total |
|---|---|---|---|
| Site lighting | 20 | 100 | 2,000 W |
| Split AC units | 4 | 2,500 | 10,000 W |
| Concrete mixer | 1 | 5,000 | 5,000 W |
| Computers & office | 5 | 500 | 2,500 W |
| Total | 19,500 W | ||
Step 3: Add Safety Margin
Add 25% to 30% above total loads to cover starting currents and unexpected demands. In our example: 19,500 × 1.25 = 24,375 W ≈ 25 kW. You'd need at least a 30 kW generator.
Quick Guide: Which Generator for Which Use?
| Generator Size | Ideal Use | Examples |
|---|---|---|
| 10 – 30 kW | Small offices, limited events | Site cabin, small exhibition |
| 50 – 100 kW | Medium construction sites, events | Villa construction, wedding |
| 150 – 300 kW | Large projects, small factories | Residential project, production |
| 400 – 1000 kW | Mega projects, complexes | Commercial project, field hospital |
Important Tips When Choosing a Generator
- Don't run at max capacity: The ideal load is 70–80% of maximum capacity for longer life and better efficiency.
- Choose the right fuel: Diesel is more efficient and cost-effective for continuous operation. Gasoline is lighter and quieter for light use.
- Noise level: For events and residential areas, choose silent generators with sound-dampening enclosures.
- Ventilation: Ensure adequate airflow around the generator to prevent overheating.
- Regular maintenance: Generators need regular oil and filter changes for optimal performance.
Let Us Help You Choose the Right Generator
We provide generators from 10 kW to 1,000 kW with delivery, installation, and maintenance. Contact us at +966 58 069 9998 or via our contact form.
FAQ
What's the difference between kW and kVA?
kW is the actual usable power, while kVA is the apparent power. The relationship: kW = kVA × 0.8 (power factor). When choosing, focus on kW.
Can I run air conditioners on a generator?
Yes, but AC units need starting current up to 3x their normal draw. Choose a generator with enough capacity to handle this surge.
How much fuel does a generator consume?
Depends on load and capacity. As a rule of thumb, a 100 kW diesel generator consumes approximately 20–25 liters/hour at 75% load.