Complete Guide to Generator Sizing in Kenya

Why Generator Sizing Matters

Choosing the wrong generator size is one of the most common and costly mistakes we see at Emerson Energy. An undersized generator won't power your essential equipment, while an oversized one wastes fuel and money.

After 20+ years of installing generators across Kenya, here's our complete guide to getting it right.

Step 1: List Your Power Requirements

First, identify everything you need to power during an outage:

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Essential Loads (Must Have)

Lighting - LED bulbs use 7-15W each, incandescent use 60-100W

Refrigerator - 100-400W running, 1,200-2,000W starting

Phone chargers - 5-10W each

Laptop - 50-100W

WiFi router - 10-20W

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Comfort Loads (Nice to Have)

Television - 80-200W

Fans - 50-100W each

Air conditioner - 1,000-5,000W (depends on BTU rating)

Water heater - 1,500-4,500W

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Business Loads (For Offices/Shops)

Desktop computer - 200-500W

Printer - 50-500W (laser printers draw more)

POS machine - 30-50W

Security system - 50-200W

Cold room - 3,000-10,000W

Step 2: Calculate Total Wattage

Add up all your running watts, then account for starting watts (motors need 2-3x running watts to start).

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Formula: Total Running Watts + Highest Starting Watts = Minimum Generator Size

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Example Calculation: Item Running Watts Starting Watts | |

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-| 10 LED lights 100W 100W | Refrigerator 200W 1,200W | TV 150W 150W | 2 Fans 160W 160W | WiFi Router 15W 15W | Total 625W N/A |

Minimum size: 625W + 1,200W (fridge starting) = 1,825W

For safety, add 20-25%: 1,825W x 1.25 = 2,280W minimum

Recommended: 3kVA generator (accounts for future additions)

Step 3: Consider These Kenya-Specific Factors

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Altitude Adjustment Nairobi is at 1,795m altitude. Generators lose about 3.5% power per 300m above sea level.

Derating for Nairobi: Multiply needed watts by 1.2 to compensate.

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Power Factor Kenya uses 50Hz power. Most generators are rated at 0.8 power factor.

Formula: kVA x 0.8 = kW available

A 10kVA generator provides ~8kW actual power.

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Voltage Requirements

Single phase: 240V (homes, small businesses)

Three phase: 415V (industrial, large motors)

Generator Sizing Quick Reference Table

Application Recommended Size Notes | |

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-| Small apartment 2.5-3.5 kVA Lights, fridge, TV, phones | 3-bedroom house 5-7.5 kVA Add AC or water heater | Large home 10-15 kVA Multiple ACs, full backup | Small shop 5-10 kVA Lighting, refrigeration | Medium office 15-25 kVA Computers, AC, equipment | Restaurant 25-50 kVA Kitchen equipment, cold rooms | Factory 50-500+ kVA Industrial motors, machinery |

Fuel Consumption Guide

At 75% load (efficient operation):

Generator Size Diesel (L/hr) Petrol (L/hr) | |

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| 5 kVA 1.2-1.5 2.0-2.5 | 10 kVA 2.5-3.0 N/A (diesel only) | 20 kVA 4.0-5.0 N/A | 50 kVA 10-12 N/A |

Common Sizing Mistakes to Avoid

1. Ignoring starting watts - Motors need 2-3x power to start 2. No room for growth - Always add 20-25% buffer 3. Forgetting power factor - kVA ≠ kW 4. Altitude ignorance - Critical in highland areas 5. Single device focus - Consider everything running simultaneously

Need Expert Help?

Our team has sized thousands of generators across Kenya. For a free consultation:

📞 Call: +254 768 860 665 or +254 782 914 717 📍 Visit: Our showroom in Nairobi 💬 WhatsApp: Send your power bill for instant sizing

We'll analyze your actual consumption and recommend the perfect generator size, brand, and model for your specific needs.

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*Published by Emerson Energy - Kenya's trusted power solutions partner since 2005*