Free tool

Event power calculator

Put in what you are hanging. It gives you the amps per leg, the breaker or feed to ask for, and the generator size — and it shows the two bits of arithmetic people drop.

This is a planning estimate, not an electrical design. It does not know your venue, your cable runs, your voltage drop, the ambient temperature or your local code. A qualified electrician signs off the tie-in. Use this to order the right feed, not to wire it.

Your rig

The supply

What you are plugging into: Power factor of the load:

A worse power factor means more current for the same watts, not less. If you are not sure, 0.9 is a safe middle.

The two things people get wrong

1. Dropping the √3 on three phase

On a three-phase supply the current per leg is watts ÷ (volts × √3), not watts ÷ volts. Ten kilowatts on a 208 V three-phase distro is 27.8 amps a leg. Drop the √3 and you get 48 amps, and you order a 60 amp feed you never needed. It is an expensive way to be careful.

2. Sizing the breaker to the load

A load that runs more than three hours is a continuous load, and a breaker may only carry 80% of its rating continuously. A show is continuous. So 40 amps of rig needs a 50 amp breaker, not a 40 — size it to the load and it trips in the second hour with the house in.

And one for generators: kVA is not kW

Generators are sold in kVA and rated at 0.8 power factor. So 20 kW of rig is a 25 kVA set, not a 20. Ask for the kW number and you get a set that is 20% too small, and it browns out the moment the moving lights all home at once.

Doing this on the actual show

A calculator is a sanity check. The real question is what is hanging where, and that is what 3D Event Builder is for — lay out truss, video walls, stages and rigging in 3D at real size, with real part numbers, and the pull sheet counts itself. It runs in a browser. Seven days free.