Grip & Electric (G&E)
Film Set Lighting Power & Circuit Load Calculator
Calculate electrical amperage draw, 80% safety headroom, and prevent blown circuit breakers on location shoots.
Add every light, monitor, and charging bank sharing the same wall circuit breaker.
The Grip & Electric (G&E) Location Power Guide
Tripping a circuit breaker on an indie set wastes valuable production time and can damage sensitive digital camera sensors, solid-state media drives, and ballast electronics. Understanding how electricity flows on location is a core safety skill for every director of photography, gaffer, and camera assistant.
1. The Paper Amp Formula: Watts / Volts = Amps
Electrical power is governed by Watt's Law, mathematically expressed as Power (Watts) = Voltage (Volts) × Current (Amps). To quickly calculate the electrical current any light draws from a wall outlet, divide the fixture's power draw by the line voltage. For example, a 1200W HMI light running on a standard 120V US outlet draws 10 Amps of current (1200 / 120 = 10A).
2. The 80% Continuous Load Rule
National electrical codes specify that standard thermal-magnetic circuit breakers must not exceed 80% of their maximum rated capacity for continuous loads (defined as any electrical draw lasting three hours or more). On a standard 15-Amp household circuit in North America, your continuous load ceiling is 12 Amps (1,440 Watts). On a 20-Amp commercial circuit, the continuous limit is 16 Amps (1,920 Watts). Operating above 80% causes breaker thermal elements to heat up and trip unpredictably mid-take.
3. Mapping Location Outlets and Breaker Panels
Never assume two physical wall sockets belong to different electrical circuits. In residential houses and offices, four to eight wall outlets across multiple rooms are frequently wired in series to a single 15A breaker. Before plugging in large LED fixtures or hair/makeup stations, send an electrician or production assistant to map the circuit breaker panel using a receptacle tester or circuit breaker finder tool.
4. Stinger Cable Gauges & Heat Dissipation
Extension cords (called "stingers" on film sets) resist electrical flow, generating heat along the copper wire. The American Wire Gauge (AWG) system measures wire thickness, where smaller numbers denote thicker wire:
- 14 AWG: Rated up to 15 Amps for short runs under 50 feet. Suitable for smaller LED panels and monitor stations.
- 12 AWG: Standard film set workhorse stinger. Rated for 20 Amps up to 100 feet with negligible voltage drop.
- 10 AWG: Heavy-duty stinger for continuous high-draw fixtures (1200W+ spotlights) or long distance runs from generators.
Always fully uncoil stingers and cable reels before powering on lights. Leaving a coiled cable carrying heavy amperage creates an induction coil that traps heat, melting insulation and creating a severe fire hazard.
Worked examples: what each circuit will actually carry
The tool treats 80 per cent of the breaker rating as the safe load. Four of its voltage and breaker combinations are shown below. The last column rounds down, because a fixture that only partly fits still trips the breaker.
| Circuit | Voltage | Breaker | Theoretical | Safe continuous | 300 W fixtures |
|---|---|---|---|---|---|
| US 15 A | 120 V | 15 A | 1,800 W | 1,440 W | 4 × 300 W |
| US 20 A | 120 V | 20 A | 2,400 W | 1,920 W | 6 × 300 W |
| UK 13 A | 230 V | 13 A | 2,990 W | 2,392 W | 7 × 300 W |
| EU 16 A | 230 V | 16 A | 3,680 W | 2,944 W | 9 × 300 W |
Working to the theoretical figure is how location shoots trip breakers. An American 15 amp circuit is nominally 1,800 watts and safely carries 1,440, which is four 300 watt fixtures rather than six.
Two further things the arithmetic does not show. Everything else on the circuit counts, including the kettle in the room next door, because domestic wiring rarely matches the room layout. And LED fixtures draw a surge at switch-on above their running figure, which the tool does not model, so leave some room below the safe limit.