How much power does my event need? Event power calculator

The short answer

Add up the running load of everything on the event in watts, divide by the power factor (about 0.9) to get kVA, then add about 25% headroom for starting loads and late additions to size the generator. Spread single-phase loads evenly across L1, L2 and L3 so no phase carries much more than the others. Event power runs at 230V single-phase and 400V/415V three-phase, never 110V.

Event power calculator

Power factor

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How it works

Load: watts from each item's rating plate, times how many.
kVA: kW divided by the power factor. 0.9 is a sensible planning figure for a mixed event load.
Phase current: single-phase loads draw watts ÷ (230 × power factor) on their phase. Three-phase loads draw watts ÷ (1.732 × 400 × power factor) on each phase.
Generator: total kVA plus 25%, rounded up to the next common size.

Before you rely on it

Event power must be designed, installed and inspected by a competent person, following BS 7909.
Check voltage drop on long cable runs with our cable size calculator.
Use RCD protection where the public or crew can reach, and protect cables across public routes.

Questions we get asked

What size generator do I need for an event?

Add up the running watts, divide by about 0.9 to get kVA, then add 25%. A 40kW event load is about 44kVA, so plan around a 60kVA generator. Our calculator does the sums and checks the phase balance.

Why does phase balance matter?

A three-phase generator is sized by its busiest phase. If one phase carries far more than the others, you need a bigger generator than the total load suggests, and the neutral carries more current. Spread single-phase loads evenly.