Festival Lighting Power Load Calculator
Calculate the total power draw of a festival lighting rig — fixture by fixture — with per-phase distribution, estimated neutral current (including the triplen-harmonic current non-linear LED loads push down the neutral even on a balanced rig), kW and kVA, a recommended generator size, and the required service size with the NEC 80% continuous-load rule applied. Handles both 120V line-to-neutral loads (standard lighting) and 208V line-to-line loads (chain motors, 208V video and distro). Enter the service you actually have on site — in amps or kVA — for a go/no-go headroom check. Built for tour managers, lighting designers, and festival production crews planning power distribution.
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Last reviewed: April 2026Report an error
Fixtures & Loads
Default workflow: enter your fixtures and the calc auto-balances them across all 3 phases — what a competent distro tech does on-site. Toggle "Manual phase assignment" above only if you're spec'ing a fixed distro layout.
Amps per leg from your tie-in spec — gives a go/no-go headroom check.
Drives the neutral-current estimate. LED switching supplies push 3rd-harmonic current down the neutral even when the legs are balanced.
Recommended Service Capacity
60 A
16.1 kW / 16.9 kVA on 208V 3-phase. Worst leg (L1): 47 A, 0.0% imbalance. Neutral ≈ 28.2 A. Spec 60A service per leg + a 25 kVA generator (NEC 80% rule).
Per-Phase Breakdown (auto-balanced)
Imbalance: 0.0%
L1WORST
47 A
5,360 W
L2
47 A
5,360 W
L3
47 A
5,360 W
Worst-case sanity check (if everything lands on one leg)
Absolute maximum: 140.9 A on one leg → would need 200 A service per leg (NEC 80% rule). For comparison, your auto-balanced spec is 60 A. If your distro layout is constrained or untested, plan toward the worst case.
Estimated Neutral Current
28.2 A
Imbalance portion: 0 A · Harmonic portion: 28.2 A
Real Power
16.1 kW
16,080 W
Apparent Power
16.9 kVA
load before margin
Generator Size
25 kVA
continuous-duty
Worst-Leg Amps
47 A
Service Capacity
60 A
Per-Phase Load Distribution
The L1 bar (highlighted) is the worst leg — service must be sized to this. Dashed red line shows your recommended service capacity after applying the NEC 80% rule.
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The Formula
- P_fixture = Watts per fixture (from spec sheet)
- PF = Power factor (LED ~0.95, magnetic ballast ~0.85)
- V_LL = Line-to-line service voltage (208 V for 3-phase festival service)
- V_LL/√3 = Line-to-neutral voltage (per leg, ~120 V on 208V service)
- 0.80 = NEC 80% continuous-load rule — applied to the breaker and the generator alike
- kVA = Apparent power = real power (kW) ÷ power factor — what distros and gennies are rated in
- L-L amps = 208V line-to-line load current — carried by BOTH legs of its pair (motors, 208V video/distro)
- Leg total = Phasor (vector) sum of a leg's line-to-neutral and line-to-line currents at their voltage angles. Balanced delta → √3 · I_pair, not 2 · I_pair.
- imbalance = Fundamental neutral current from L-N loads: √(I₁²+I₂²+I₃² − I₁I₂ − I₂I₃ − I₃I₁)
- harmonic = Triplen-harmonic neutral current from non-linear LED loads: k × avg leg current (k ≈ 0 linear, 0.25 mixed, 0.6 non-linear)
Source: NEC 2023 Article 210.20 ↗
How to Use This Festival Power Calculator
- 1Add each fixture: name, watts, count, connection type (120V line-to-neutral or 208V line-to-line), and phase assignment.
- 2Pick service voltage (208V 3-phase is standard for festivals).
- 3Set power factor (LED ~0.95, arc/discharge ~0.85).
- 4Optional: set fixture load type (all-LED rig = non-linear) and your available on-site service — in amps or kVA — for a headroom check.
- 5Read per-phase amps, neutral current, kW/kVA, recommended service size, and generator size.
Frequently Asked Questions
- A mid-size festival main stage might pull 400-800A on 208V 3-phase. A small club rig might be 100-200A. Headlining tours can hit 1500A+ with multiple LED walls and large lighting.
- Power factor is the ratio of real power (watts) to apparent power (volt-amps). LED fixtures with switching power supplies are near 1.0 (efficient). Older arc/discharge fixtures with magnetic ballasts run 0.8-0.9 — meaning more amps drawn than the wattage suggests.
- 3-phase 208V is industry standard because it splits the load across three legs, cutting current per leg by 1.73x. Single-phase 240V is used for smaller rigs (<10,000W). Generators almost always output 3-phase for events.
- Most festival lighting runs 120V line-to-neutral — one hot leg plus the neutral. But chain motors, some 208V LED video processors, and 208V distro feeds run line-to-line: across two hot legs, with no neutral. They draw current differently, and a 208V line-to-line load puts current on both of its legs at once. Set each fixture group's connection type so the per-leg amps come out right — and so the neutral estimate correctly excludes the 208V loads, which have no neutral path.
- Not by simple addition — a 208V line-to-line current and a 120V line-to-neutral current sit at different voltage angles, 60° apart in the balanced case. The leg total is the PHASOR (vector) sum of every current touching it. The headline consequence: a balanced 3-phase delta load (three equal 208V loads, one on each pair) gives the textbook I_line = √3 × I_pair per leg, NOT 2 × I_pair. A naive scalar add over-states the per-leg amps by roughly 15% and would push your service one breaker size larger than it actually needs. The calculator uses the proper phasor sum so the numbers match what a licensed electrician would compute by hand.
- Two reasons. Any imbalance between the three legs returns on the neutral — that part is zero when the rig is perfectly balanced. But LED fixtures and any switching power supply draw current in sharp pulses rich in 3rd-harmonic content, and those triplen harmonics are in phase on all three legs, so they add up in the neutral instead of cancelling. A balanced all-LED rig can still push 50-70% of a hot leg down the neutral. NEC 220.61 treats the neutral as a current-carrying conductor for non-linear loads — size it at least equal to the phase conductors.
- kVA. Watts (kW) is real power — the work your fixtures do. kVA is apparent power — what the generator, distro, and cables physically have to carry. They differ by power factor: kVA = kW / PF. Generators and distros are rated in kVA, so always spec to the kVA figure. A 50kW rig at 0.9 power factor needs a generator rated for about 56kVA.
- Use the kVA figure, not kW — generators are rated in kVA, and sizing to watts alone under-specs the genny. Add headroom on top, since generators derate at high temperatures and altitudes. If you already have the tie-in or generator spec, enter it as your available service for a direct headroom check.
- Many fixtures (especially older tungsten or arc) have 3-5x inrush at turn-on for ~100ms. Modern LED fixtures with soft-start are negligible. For old racks, use a phased turn-on sequence to avoid breaker trips.
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