General Lighting Loads

When you are calculating the total electrical load for a building — whether to size a panel, feeders, or service entrance — you need a starting number for lighting. Instead of counting every fixture, the NEC lets you use a simple multiplier based on the building's square footage and occupancy type. For a house, you multiply the square footage by 3 VA per square foot. For an office, you multiply by 2 VA. For a warehouse, you use a much lower 0.25 VA per square foot. The floor area is calculated from the outside dimensions of the building and includes all habitable floors. For dwelling units, you exclude open porches, garages, and unfinished spaces that cannot be adapted for future use. These numbers represent the minimum general lighting load for your calculations — your actual lighting design may end up using more or less energy, but this is the code-required starting point for sizing the electrical infrastructure.