Power Load Calculations

This SOP defines the standards and procedures for calculating, verifying, and documenting electrical loads for all MP/RV events. Accurate load calculations are essential for safe power distribution, system reliability, and preventing breaker trips, voltage drop, or equipment damage.

Load calculations must be completed before power systems are deployed.

Purpose

  • Ensure all power systems are operated within rated limits.

  • Prevent overloads, phase imbalance, and unsafe conditions.

  • Standardize how electrical loads are calculated and documented.

  • Support coordination between technical departments.

  • Provide a defensible reference for power planning decisions.

Who This SOP Is For

  • Power technicians

  • Lighting, audio, and video leads

  • Technical Directors

  • Project Managers responsible for power scope

  • Warehouse staff assisting with prep

Anyone planning or approving power systems must understand load calculations.

Scope

This SOP applies to:

  • Feeder and distro load planning

  • Lighting, audio, video, and auxiliary systems

  • Temporary power and generator systems

  • Indoor and outdoor event power

This SOP does not replace licensed electrical engineering where required.

Load Calculation Fundamentals

  • All loads must be known or conservatively estimated.

  • Continuous loads must be derated appropriately.

  • Phase balance is critical for three-phase systems.

  • Neutral current must be considered.

  • Diversity factors must be used cautiously.

Guessing loads is unacceptable.

Load Data Sources

Use the most accurate available data:

  • Manufacturer specifications

  • Nameplate ratings

  • Power monitoring tools

  • Historical job data

  • Bench testing when required

When in doubt, assume worst-case.

Department Load Breakdown

Lighting

  • Fixture wattage (maximum draw)

  • Quantity of fixtures

  • Control and network devices

  • Consoles and peripherals

Lighting loads often dominate the system.

Audio

  • Amplifier maximum draw

  • Console and processing gear

  • RF racks and accessories

Account for peak draw during transients.

Video

  • LED wall processors and tiles

  • Projectors

  • Cameras and switchers

  • Playback systems

Video systems may have high inrush current.

Auxiliary & Support

  • FOH power

  • Network switches

  • Charging stations

  • Work lights

  • Specialty effects

Small loads add up.

Single-Phase Calculations

For single-phase loads:

  • Watts = Volts × Amps

  • Calculate amperage based on maximum wattage.

  • Apply derating for continuous loads.

Example: - 120V × 10A = 1200W

Three-Phase Calculations

For balanced three-phase loads:

  • Watts = √3 × Volts × Amps

  • Balance loads evenly across phases.

  • Avoid excessive neutral current.

Unbalanced systems increase risk.

Continuous Load Derating

  • Continuous loads (>3 hours) should not exceed: - 80% of circuit rating

  • Apply derating to: - Breakers - Feeder - Distro outputs

Derating provides safety margin.

Phase Balancing

  • Distribute loads evenly across phases.

  • Avoid concentrating high-draw equipment on one phase.

  • Monitor neutral current.

  • Rebalance if changes occur.

Phase imbalance causes inefficiency and overheating.

Generator Load Planning

  • Calculate total connected load.

  • Add startup and inrush margins.

  • Target 60–80% generator capacity.

  • Account for fuel consumption and runtime.

  • Avoid last-minute load additions.

Generators must never be maxed out.

Documentation Requirements

Load calculations must be documented for:

  • Large or complex shows

  • Generator-powered events

  • Multi-distro systems

  • Outdoor events

Documentation should include: - Load list by department - Phase assignments - Total and per-phase load - Safety margin

Documentation supports accountability.

Verification & Testing

  • Verify calculations against real-world measurements.

  • Use power meters when available.

  • Monitor loads during setup and show.

  • Adjust as needed.

Calculated loads must match reality.

Changes & Additions

  • Any load changes must be reviewed.

  • Recalculate affected circuits.

  • Do not add equipment without approval.

  • Communicate changes immediately.

Unplanned additions cause failures.

Responsibilities

Power Technicians

  • Perform and verify load calculations.

  • Balance phases.

  • Monitor loads during operation.

Department Leads

  • Provide accurate equipment lists.

  • Communicate changes promptly.

Project Managers

  • Ensure load planning is completed.

  • Approve scope changes affecting power.

Warehouse Staff

  • Provide accurate equipment data.

  • Assist with prep verification.

Quality Control

  • No system energized without load planning.

  • Loads remain within rated limits.

  • Phase balance maintained.

  • Documentation completed when required.

Load calculation discipline prevents outages.