In the NEC, what does the term 'unit load' refer to in respect to lighting load calculations?

In the National Electrical Code (NEC), the term 'unit load' refers specifically to volt-amperes per square foot. This measurement is crucial in determining the lighting load for different types of spaces when calculating electrical service requirements.

Using volt-amperes per square foot allows for a standardized approach to estimate the power demands of lighting systems in various environments, taking into account not only the wattage of the lighting fixtures but also their efficiency and the overall electrical characteristics of the systems being designed.

This method is essential for ensuring that electrical installations are adequate for the intended use, contributing to efficient design and safety. Volt-amperes capture both the real and reactive power involved in lighting systems, reflecting a more comprehensive view of electrical consumption than merely measuring in watts, which does not account for power factor.