What is the general purpose receptacle load calculation recommended by NEC?

The National Electrical Code (NEC) recommends a general-purpose receptacle load calculation of 180 volts-amperes (VA) per outlet for dwelling units. This figure is established to ensure that residential electrical systems are adequately designed to handle the expected load from general-purpose outlets, which can be used for a variety of devices such as lamps, appliances, and electronics.

Using 180 VA per outlet provides a conservative estimate that allows for diversity in load usage, meaning that not every outlet will be used at full capacity at the same time. This approach ensures safety and efficiency in electrical design and helps prevent overloading circuits.

In the context of the other options, the reasons for their inaccuracy relate to the NEC's established standards, as a figure higher than 180 VA could lead to oversizing of the electrical system, resulting in unnecessary costs in materials and installation. Conversely, a number lower than 180 VA may not provide sufficient capacity for expected demands, potentially leading to circuit failure or safety hazards. Thus, 180 VA aligns well with the NEC’s intention to balance safety, reliability, and cost.