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Power & Generator

Work out the current per phase and the generator size for your rig from the total load, single or three phase. Updates live as you type.

5 · Power Draw & Generator Sizing

Current per phase and the generator you need.

Single: I = W ÷ (230 × PF). 3-phase: I per leg = W ÷ (√3 × 400 × PF). Genset kVA ≈ (W ÷ PF ÷ 1000) × surge. Balance loads across legs.

About this calculator

Work out the current per phase and the generator size for your rig from the total load, single or three phase. Updates live as you type.

Questions

How do I size a generator for an event?

Take the total continuous load in watts, divide by the power factor to get kVA, then multiply by a surge or headroom factor (around 1.25) so motor and amplifier inrush does not stall the set. Never load a generator to 100 percent; leaving headroom keeps the voltage and frequency stable.

How do I work out the current per phase?

For a single-phase 230 V supply, current equals watts divided by (230 times the power factor). For a three-phase 400 V supply, current per leg equals watts divided by (root-three times 400 times the power factor). Spreading load evenly across the three legs keeps each leg within its breaker.

What is power factor and why does it matter?

Power factor is the ratio of real power (watts) to apparent power (VA). Switch-mode gear like LED and audio amps often runs around 0.9. A lower power factor means more current and a bigger generator for the same watts, so it directly affects the size you need.

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