How to Calculate Temporary Site Power Capacity
Site power requirement is calculated as: Required kVA = Total Wattage ร Demand Factor รท Power Factor รท 1000. The demand factor (0.75 default) reflects that not all equipment runs at peak load simultaneously. Power factor (0.8 default) is the ratio of real power to apparent power โ motor loads draw more apparent power than their nameplate wattage suggests.
When sizing a generator, select one rated at least 1.25ร the calculated kVA to handle startup surges from motors. Common construction generator sizes are 20, 30, 50, 100, and 200 kVA โ choose the next standard size above your result.
Add all powered equipment using the table, enter the correct wattage per unit, adjust demand and power factors to match your site conditions, then click Calculate.
Frequently Asked Questions
Check the equipment nameplate or product manual. Nameplate values are usually rated at full load. Some equipment lists amperage โ multiply by voltage to get watts (P = V ร I).
This is a planning tool for temporary power estimation. For permanent electrical installations, consult a licensed electrician โ local codes and load calculations must be followed.