How to Calculate Diesel Generator Capacity

Correct capacity calculation prevents equipment failure and wasted cost.

Step 1: List Loads

List all power-consuming equipment with wattage or kilowatt rating. Include lighting, motors, pumps, HVAC and office equipment.

Step 2: Calculate Motor Loads

Motor loads (pump, fan, compressor) have high starting factors. Multiply their power by 1.25 to 3.

Step 3: Sum Total Load

Add all loads and add 20% for future growth.

Step 4: Apply Derating

If installed above 1000m altitude or 25°C temperature, apply power reduction factor.

Step 5: Choose Final Capacity

Choose a generator that covers 70-80% of calculated load. Never choose at 100% capacity.