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 generators (0.5-10 KVA): Cheapest to buy, common for small homes. Popular brands: Sumec Firman, Tiger, Elepaq, Honda
- Diesel generators (5-500+ KVA): More fuel-efficient, longer-lasting, better for businesses. Popular: Mikano, FG Wilson, Perkins, Caterpillar
- Inverter generators (1-7 KVA): Quieter, more fuel-efficient, better for electronics. Growing in popularity
- Solar + inverter systems: No fuel cost, silent, increasingly affordable. Best for consistent loads
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.