Consumer and small commercial electrical lines must be buried between 6 and 24 inches underground, while large commercial and industrial lines must be buried between 30 and 36 feet underground. Electrical lines for carrying current to a home or building must be buried deep enough to avoid digging accidents by homeowners and others.
Consumer or small commercial lines are often encased in different gauges of conduit before being buried at a depth of 24 inches. Electrical lines may be buried at other depths as well. For example, some projects use a depth of 6 inches when the line is encased in half-inch gauge metal conduit with waterproof conductors.
Direct-bury underground feeder (UF-B) line can be buried at a depth of 12 inches if it meets certain criteria. It must have GFCI protection before it is buried and the line being buried is limited to 120 volts and must use no higher than a 20-amp fuse or breaker.
THWN-2 conductors inside PVC must be buried at a depth of 18 inches, while UF-B line must be buried at 24 inches or deeper.