For a 20 amp load, what size THHN wire should be used?

In the context of a 20 amp load, the appropriate size of THHN wire is 12 gauge. This is because wire gauge is closely related to its current-carrying capacity, which is determined by its diameter and material. For copper wire, the National Electrical Code (NEC) recommends that a 12-gauge wire can safely handle up to 20 amps for general purposes under normal conditions.

Selecting a wire size that matches the load is crucial for ensuring safety and efficiency in electrical installations. A wire that is too small for the load can overheat and potentially cause a fire hazard, while a wire that is too large might be unnecessary and unnecessarily costly. Therefore, 12-gauge wire is the standard choice for a 20 amp load, providing a balance of safety and efficiency.