How to Choose the Right Generator Size (kVA) for Your Business – Avoid These Common Mistakes

Generator man
23 hours ago
2 min read

One of the most frequent questions we get at GES Power is: “What size generator do I need?”

Getting the kVA rating right is critical. Choose too small and it won’t handle your loads. Choose too big and you’ll waste money on purchase, installation, and running costs.

Here’s a practical guide to help you get it right.

Why Generator Sizing Matters

A generator’s kVA rating tells you how much power it can safely deliver. Undersized generators can overheat, trip out, or fail under load. Oversized ones run inefficiently, use more fuel, and cost more upfront.

Step-by-Step Guide to Sizing Your Generator

1. List All Your Critical Equipment

Make a full inventory of everything that must stay on during a power cut:

Refrigeration / freezers
Lighting
Computers & servers
Pumps and motors
Air conditioning or heating
Medical or security equipment

2. Calculate Running and Starting Loads

Running (rated) power – what each item uses normally (in kW or kVA)
Starting surge – motors and compressors can draw 2–3 times more power when starting

3. Apply Diversity Factor Not everything runs at full load at the same time. A good diversity factor is often 0.7–0.8 for many businesses.

4. Add Future Expansion It’s wise to add 20–30% headroom for future growth.

Common Sizing Mistakes to Avoid

Ignoring starting surges – especially with large motors or multiple compressors.
Forgetting power factor – most generators are rated at 0.8 power factor.
Only considering average load – you must size for the peak demand.
Buying purely on price per kVA – reliability and brand matter more in the long run.

Quick Examples

Small retail shop or office → 20–45kVA
Food processing / cold storage → 80–300kVA+
Factory with heavy machinery → 200–1000kVA+
Farm or off-grid home → 8–50kVA

Let the Experts Help

While the above gives you a good starting point, accurate sizing requires proper load analysis. At GES Power we offer free site surveys and load calculations as part of our service.

We’ll visit your site, measure actual consumption, and recommend the perfect generator (with the right engine, canopy, and control panel) for your needs and budget.

Stop guessing and get it right first time.

📞 01246 380525 ✉️ hello@generator-man.co.uk

GES Power Ltd – Your trusted partner for reliable diesel generator solutions across the UK.