Higher-voltage lines are a small share of the grid but carry most of the power
The U.S. transmission network spans 422,000 miles across six voltage classes.
Lines at 345 kV and above represent just 23% of total line-miles but account for
63% of power-carrying capacity. HVDC, measured by thermal ratings rather than AC surge impedance,
is the most land-efficient technology per unit of power moved.
422,429Total line-miles
86,901GW-miles capacity
52,244Lines
489Owners
Line-Miles vs. GW-Miles by Voltage Class
Line-miles (physical distance)
GW-miles (power × distance)
Land Use: Right-of-Way per Unit of Capacity
Higher-voltage lines need wider corridors—275 ft for 765 kV vs. 85 ft for 115 kV.
But because AC power capacity scales with V², the right-of-way per GW drops sharply with voltage.
HVDC, with no reactive losses and just two conductors, is the most land-efficient of all.
Physical ROW Width
ROW to Move 1 GW
The land cost of low voltage
Right-of-way to carry 1,951 MW—the thermal capacity of a single 765 kV line
115 kV
36 parallel lines
765 kV
1 line
11.2×
more land at 115 kV
Acres of Right-of-Way per GW-Mile
Most of the land goes to the smallest lines
The U.S. transmission grid occupies 6 million acres of right-of-way—roughly the size of New Hampshire.
Lines at 100–161 kV consume 40% of that land but deliver just 15% of power capacity.
Lines at 345 kV and above use 38% of the land and deliver 67% of the power.
6.0MAcres of ROW
9,451Square miles
0.25%of contiguous U.S.
Total Right-of-Way Acres vs. GW-Miles by Voltage Class
Data: HIFLD Electric Power Transmission Lines (52,244 features, Feb 2026). AC capacity: surge impedance
loading (SIL = V² / 300Ω). HVDC capacity: known thermal/converter ratings by project.
Right-of-way widths: typical U.S. utility standards (EPRI, FERC siting guidelines).
Distances: Haversine formula on polyline geometry. Population: 335M (2025 est.).
Source: Homeland Infrastructure Foundation-Level Data (HIFLD), via ArcGIS Feature Service.
See also: Macrogrid expansion analysis | Interactive map.