What is the minimum vertical clearance required for service-drop conductors over a residential driveway, measured at final grade?
Not quite. The answer is C: 12 feet
230.24(B) sets 12 feet as the minimum clearance for service-drop conductors over residential property and driveways for the common 120/208 V, 120/240 V and 277/480 V systems (the figure rises to 15 feet where the system exceeds 300 V to ground). Public streets, alleys, and commercial areas subject to truck traffic require the higher 18-foot clearance instead — confusing the residential and commercial clearance figures is a common exam trap.
Reference: NEC 2023 230.24(B) (Service Drop Clearances)
Checked against multiple published sources
A Mike Holt 2023 NEC series article and an ECM services article both give 12 ft over residential property and driveways in 230.24(B). The 2023 text frames this by system voltage (120/208, 120/240, 277/480 V) rather than the older 300 V-to-ground wording. Neither is the code text.