Generator Size Calculator — What KVA Do You Need?

Your Appliances

Generator Recommendation

Running Watts

Startup Watts (Peak)

Recommended KVA

Power Factor

0.8

Power in Africa

Power instability is a daily reality across much of Africa. Nigeria alone has over 60 million generators in use. Choosing the right size saves fuel costs and protects your appliances.

Undersized generator: Overloads, trips, and damages appliances and the generator itself.

Oversized generator: Wastes fuel, increases purchase cost, and may cause wet stacking (diesel).

Sweet spot: Generator should run at 50-75% of capacity for optimal efficiency and lifespan.

KVA vs KW

KW (Kilowatts) = actual power consumed by your appliances.

KVA (Kilovolt-Amperes) = apparent power the generator must produce.

KVA = KW / Power Factor

Most generators have a power factor of 0.8, meaning a 10 KVA generator delivers about 8 KW of usable power.

How to Size a Generator for Your Home or Business

Choosing the right generator size is critical in countries with unstable power supply. An undersized generator will overload and potentially damage your appliances, while an oversized one wastes money on purchase and fuel. This calculator helps you find the sweet spot by totalling the wattage of all your appliances and accounting for startup surge requirements.

Understanding Startup Surge

Many appliances, especially those with motors (air conditioners, refrigerators, pumps, washing machines), require significantly more power to start than to run continuously. This startup surge can be 2-3 times the running wattage. Your generator must handle this peak load, even though it lasts only a few seconds. This calculator automatically factors in surge requirements.

Generator Types Common in Africa

Petrol, diesel and inverter sets: compare manufacturer duty, fuel, noise, service support and verified output rather than choosing by size alone.
Solar and battery systems: require separate energy, autonomy, inverter and battery sizing; generator kVA is not a solar design.

Frequently Asked Questions

What size generator do I need for a 3-bedroom flat in Nigeria?

A typical 3-bedroom flat running lights, fans, TV, refrigerator, and a few small appliances needs about 2.5-3.5 KVA. Add an AC unit and you'll need 5-7.5 KVA. Add multiple ACs and you're looking at 10+ KVA.

Why does my generator trip when the AC starts?

Air conditioners have a high startup surge — typically 2-3 times their running wattage. If your generator is only sized for running watts, the surge will overload it. You need a generator rated for the combined running watts plus the highest single startup surge.

Is it better to buy one large generator or two small ones?

One properly sized generator is usually more efficient and cost-effective. However, for businesses needing redundancy, two generators with an automatic changeover can provide backup if one fails. Some setups use a small generator for low-load periods and a larger one for peak times.

Backup power check

Verify the load schedule before buying a generator

Use the appliance list, running watts, surge watts, power factor, and headroom to create a quote-ready generator sizing brief.

Undated example presets

Local-first, low-confidence planning estimate. No live quote, manufacturer rating or electrical approval is performed.

What to check

Methodology: sum running watts, model startup surge, convert to kVA with the displayed power factor, then add practical headroom.
Confirm appliance labels, motor startup surge, phase, AVR/inverter quality, transfer switch, earthing, ventilation, noise, fuel type, and local technician advice.
Copy or download the load schedule before asking suppliers for quotes so every quote is based on the same appliance list.

Limitations

Disclaimer: planning estimate only, not an electrical certificate, safety sign-off, installer quote, warranty, or official power standard.
Real generator performance varies by altitude, heat, fuel quality, maintenance, load balance, and manufacturer surge rating.
Source/reference note: verify against current manufacturer datasheets, electrician guidance, local wiring codes, and safety rules before installation.

Review result panel

Privacy note: the calculator runs in your browser. Do not paste account numbers, installer contracts, or private customer data into notes you plan to share.