Service Drop Point of Attachment Height Calculator
Find the minimum height of the point of attachment for an overhead service drop under NEC 230.26: the 10 ft floor above finished grade, and the higher figure the governing 230.24 clearance forces when the span crosses a driveway, a street, or a truck-traffic area. Enter a proposed attachment height for a compliance check.
How to use this calculator
- Pick what the overhead span crosses: a pedestrian-only area, residential property or driveway, or a street / truck-traffic area. Leave it on "floor only" to see just the 230.26 minimum.
- For a pedestrian or residential crossing, enter the nominal voltage to ground (120 for a 120/240 V service) so the 230.24(B) clearance resolves correctly.
- Read the required minimum attachment height and whether the 230.26 floor or the 230.24(B) clearance sets it.
- Optionally enter a proposed attachment height for a compliance verdict.
- Read the verdict: meets 230.26, does not meet 230.26, or needs review when the crossing has not been stated.
NEC reference
This calculator implements NEC 2020 230.26, Point of Attachment. The point of attachment of the overhead service conductors to a building or other structure shall provide the minimum clearances specified in 230.9 and 230.24, and in no case shall it be less than 3.0 m (10 ft) above finished grade. The governing 230.24(B) vertical span clearance is read from the same audited data as the Overhead Conductor Clearance Calculator. NEC 2020 is the site default; the 10 ft minimum is worded the same in the 2017 and 2023 editions.
Results are for reference only. Verify against the applicable adopted edition of the NEC and consult a licensed electrician for code compliance.
The 10 ft floor is a minimum, not the answer
NEC 230.26 is a one-line rule with one number: the point of attachment is never less than 10 ft above finished grade. The sentence before that number is what trips installers up. The attachment must also be located so the overhead span keeps the clearances in 230.24 (above ground and roofs) and 230.9 (from building openings). Because the service drop sags down from the pole to the attachment, the attachment has to sit at least as high as the clearance the span must maintain over whatever it crosses. When that clearance is more than 10 ft, the 10 ft floor is no longer the governing number.
What the span crosses sets the real minimum
The governing vertical clearance comes from NEC 230.24(B) and depends on what is below the span and the nominal voltage to ground. The required attachment height is the larger of the 230.26 floor and that clearance.
| Crossing | 230.24(B) span clearance | Required attachment | Source |
|---|---|---|---|
| Sidewalk / pedestrian-only (≤ 150 V to ground) | 10 ft | 10 ft (floor governs) | 230.26 + 230.24(B)(1) |
| Residential / driveway (≤ 300 V to ground) | 12 ft | 12 ft | 230.24(B)(2) |
| Residential / driveway (> 300 V to ground) | 15 ft | 15 ft | 230.24(B)(3) |
| Street, road, or truck-traffic area | 18 ft | 18 ft | 230.24(B)(4) |
The 230.24(B) clearances are keyed on nominal voltage to ground, not line-to-line system voltage. A 120/240 V single-phase service is 120 V to ground; a 208Y/120 V or 480Y/277 V system is 120 V and 277 V; a 480 V delta is 480 V to ground and uses the 15 ft row.
Worked examples
A 120/240 V service drop crosses a residential driveway to a point of attachment on the house. The 230.26 floor is 10 ft, but the span must clear 12 ft over the driveway under 230.24(B)(2), so the point of attachment must be at least 12 ft above finished grade. A 10 ft attachment meets the bare floor but fails the real requirement.
A drop crosses a commercial parking area subject to truck traffic. The span must clear 18 ft under 230.24(B)(4), so the attachment has to be at least 18 ft. The 10 ft floor is far below the governing clearance here.
A drop lands on a pole-barn wall above a lawn reached only on foot, at 120 V to ground. The span clearance is 10 ft over a pedestrian-only area, the same as the 230.26 floor, so 10 ft at the attachment is the minimum. Conductor sag and the 3 ft clearance from any window that opens still have to be checked.
What this tool does not check
- Conductor sag. The attachment height is the high end of the span; the lowest point of the drop sags below it and must independently meet the 230.24 clearance.
- 230.9 from-building clearance. Open service conductors keep a separate 3 ft horizontal clearance from windows that open, doors, porches, and balconies. This is a horizontal dimension, not a height, and is cross-linked but not computed here.
- Roof and railroad spans. Clearance above a roof (230.24(A), 8 ft base) and over railroad rails (225.18, feeders) belong to the Overhead Conductor Clearance Calculator.
- The service mast and service head. 230.28 strength and support of the mast and 230.54 service-head and drip-loop rules are separate.
Frequently asked questions
How high does the point of attachment have to be?
Never less than 10 ft (3.0 m) above finished grade under 230.26, and high enough that the overhead span still meets the 230.24 and 230.9 clearances, which over a driveway (12 ft) or a street (18 ft) forces the attachment above the 10 ft floor.
Is 10 ft always enough?
No. Ten feet is the floor. If the drop crosses a driveway or a vehicle area, the governing 230.24(B) clearance is higher, and a 10 ft attachment does not comply.
Does voltage change it?
Over residential property the clearance is 12 ft at 300 V to ground or less and 15 ft above 300 V. The clearances use voltage to ground, so a 480 V delta (480 V to ground) uses the 15 ft figure.
How is 230.26 different from 230.24?
230.24 is the clearance of the span above the ground or a roof; 230.26 is the minimum height of the point where the drop attaches to the building, with a 10 ft floor and a requirement to maintain the 230.24 and 230.9 clearances.
What about clearance from windows?
230.9 requires a 3 ft clearance from windows that open, doors, porches, and balconies. That is a separate horizontal check, flagged here and covered by the Conductor Clearance From Buildings tool.
Related calculators
- Overhead Conductor Clearance Calculator: minimum vertical clearance of an overhead span above ground and roofs per NEC 230.24 / 225.18.
- Conductor Clearance From Buildings Calculator: the 3 ft clearance of open conductors from windows, doors, and balconies per NEC 230.9 / 225.19.
- Service Size Calculator: size service-entrance conductors and the grounding electrode conductor from a known load.
- Emergency Disconnect Requirement Calculator: the NEC 230.85 outdoor emergency disconnect for one- and two-family dwellings.
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