How to Choose the Right Diesel Generator for Your Business: Complete Buying Guide
Buying a diesel generator involves more than picking a kVA rating. This guide walks you through load calculation, sizing, open vs silent selection, brand considerations, and the 7 specifications that actually matter.
Rishabh Power Solutions Engineering Team
1 min read
Quick Answer
To choose the right diesel generator: (1) Calculate your total connected load in kW, (2) Add 20–25% safety margin, (3) Divide by 0.8 to convert to kVA, (4) Choose the next standard kVA rating up.
Step 1: Calculate Your Total Connected Load
| Equipment | Typical Load |
|---|---|
| Split AC (1.5 ton) | 1.5–1.8 kW |
| Desktop computer + monitor | 0.3–0.5 kW |
| Lift/Elevator (6 person) | 7.5–11 kW |
| Submersible pump (5 HP) | 3.7 kW |
| CNC machine | 5–15 kW |
| X-ray machine | 10–30 kW |
Account for Motor Starting Surge
Electric motors draw 3–6 times their running current during startup. DOL start: multiply by 3. Star-delta: multiply by 1.8. VFD/soft-start: multiply by 1.2.
Step 2: Size Your Generator
Required kVA = (Total Load in kW × 1.25) ÷ 0.8
Example: Small Office
8 ACs (12 kW) + 40 LEDs (0.96 kW) + 15 PCs (6 kW) + lift (7.5 kW) = 27.6 kW → (27.6 × 1.25) ÷ 0.8 = 43.1 kVA → 50 kVA generator
Step 3: Open vs Silent
| Feature | Open Frame | Silent/Acoustic |
|---|---|---|
| Noise | 85–95 dB(A) | 65–75 dB(A) |
| Cost | Base price | 15–30% premium |
| Best for | Factories, rural | Hospitals, hotels, offices |
CPCB requires ≤75 dB(A) at 1 metre — most open-frame units exceed this.
The 7 Specs That Matter
- kVA rating (Prime vs Standby)
- Engine make and model
- Alternator brand
- Fuel tank capacity
- Noise level (dB at 1m)
- Control panel type (Auto-start AMF)
- CPCB-IV+ compliance — read our guide
Frequently Asked Questions
What size for a 3-bedroom house?
A 3BHK with 3 ACs needs about 8–10 kW → 15–20 kVA generator.
What about a small factory?
Typically 62.5–125 kVA. Send us your load list for free sizing.
How long does a diesel generator last?
15,000–30,000 running hours before major overhaul. With regular AMC/CMC maintenance, 15–20 years in standby use.
Get Help
Request a free quote or call +91 9810145225. Browse our range — 3.5 to 1500 kVA.
Rishabh Power Solutions Engineering Team
Power engineering insights from Rishabh Power Solutions