What demand factor percentage should be applied to the nameplate rating load for at least four appliances in a single-family dwelling?

The demand factor is a crucial concept in electrical load calculations, particularly in residential settings. For a single-family dwelling, the code specifies that there can be a significant reduction in the calculated load when it comes to assessing the demand for multiple appliances that are not likely to operate simultaneously at full capacity.

When dealing with the nameplate rating load for four or more appliances, a demand factor of 25% is appropriate. This factor reflects the reality that not all appliances will be used at the same time or at their maximum load. By applying this percentage, you can more accurately estimate the actual load that needs to be supplied by the electrical system, ultimately leading to efficient and safe electrical design.

In essence, the 25% demand factor acknowledges typical usage patterns, helping to optimize the size of conductors and overcurrent protective devices while maintaining safety standards in the electrical system. This approach adheres to the National Electrical Code (NEC) guidelines, ultimately supporting better energy management in residential applications.