How big is the United States's transmission network?

OverWatts maps 239,100 km of transmission line in the United States, across 55,378 segments, plus 1,767 substations. This is mapped length from OpenStreetMap, not an operator-reported total — where OSM is incomplete the figure is a floor, never a ceiling.

What voltage is the United States's grid?

Most of the mapped network is high voltage (220–379 kV): 188,200 km of 239,100 km. The highest voltage tagged anywhere in the country is 1,333 kV.

Who operates the grid in the United States?

Florida Power & Light, ITC, Public Service Company of Colorado and 5 others are tagged as operators on mapped segments. Operator tags are present on 23% of the United States's segments, so this ranks who is *recorded*, not market share.

What interconnectors connect the United States to its neighbours?

16,568 MW of cross-border transfer capacity to Canada, Mexico, plus 4,400 MW planned. Capacities are from the Global Transmission Database (v1.0, 2023).

United States · electricity network

United States power grid

Q: How complete is the grid map for the United States?

Moderate — 25.2 km of mapped line per 1,000 km² of land, ahead of 67% of the 153 countries with any mapped grid. Coverage grades how completely OpenStreetMap has drawn the network, not how much network exists; large, sparsely-populated countries score low for geographic reasons alone.

OverWatts maps 239,100 km of the United States's electricity transmission network across 55,378 line segments and 1,767 substations, the 3rd most-mapped grid of 153 countries. Its backbone is high voltage (220–379 kV), carrying 188,200 km — 79% of the mapped length, with the highest tagged voltage at 1,333 kV. That works out to 25.2 km per 1,000 km² of land — moderate OpenStreetMap coverage, ahead of 67% of mapped countries. It is connected to 2 neighbouring grids by 16,568 MW of existing cross-border transfer capacity, with a further 4,400 MW planned.

Open the grid lens →United States profile →

239,100 km

Mapped transmission line

1,767

Substations

of 153 mapped grids

16.6 GW

cross-border · 2 neighbours

1,333 kV

Highest voltage

OpenStreetMap coverage

Moderate25.2 km / 1,000 km²ahead of 67% of 153 mapped countries

This grades how completely OpenStreetMap has drawn the United States's network — not how much network exists. Large, sparsely-populated countries score low for geographic reasons alone, and every kilometre here is mapped length, so the totals are a floor rather than an operator-reported figure. 21% of segments carry a real line name and 23% an operator tag.

Mapped line length by voltage

≥765 kV3,856 km 2%
380–764 kV47,000 km 20%
220–379 kV188,200 km 79%
<220 kV10 km 0%
Voltage untagged20 km 0%

55,378 segments · a segment is credited to the country containing its midpoint, so a border-crossing line counts once, on one side.

16.6 GW existing · 4.4 GW planned · capacities from the Global Transmission Database v0.1 (CC BY 4.0), existing as of 2023

On the interactive map

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Load against the network

1168 GW

Operating generation

Data centres mapped

135

km of line per substation

25.2

km per 1,000 km²

Where there is room to connect a new load depends on published hosting capacity, which most operators release only as their own map. OverWatts does not yet ingest those feeds, so these are the density measures the open data supports — generation and mapped demand against mapped network — not a headroom figure.

Segment counts from OSM `operator` tags, merged across spellings. Present on 23% of segments — this ranks who is recorded, not market share.

How the United States compares · mapped grid by country

1. People's Republic of China624,300 km
2. India271,000 km
3. United States of America239,100 km
4. Russia165,600 km
5. Brazil160,000 km

Frequently asked

How big is the United States's transmission network?: OverWatts maps 239,100 km of transmission line in the United States, across 55,378 segments, plus 1,767 substations. This is mapped length from OpenStreetMap, not an operator-reported total — where OSM is incomplete the figure is a floor, never a ceiling.
What voltage is the United States's grid?: Most of the mapped network is high voltage (220–379 kV): 188,200 km of 239,100 km. The highest voltage tagged anywhere in the country is 1,333 kV.
How complete is the grid map for the United States?: Moderate — 25.2 km of mapped line per 1,000 km² of land, ahead of 67% of the 153 countries with any mapped grid. Coverage grades how completely OpenStreetMap has drawn the network, not how much network exists; large, sparsely-populated countries score low for geographic reasons alone.
Who operates the grid in the United States?: Florida Power & Light, ITC, Public Service Company of Colorado and 5 others are tagged as operators on mapped segments. Operator tags are present on 23% of the United States's segments, so this ranks who is *recorded*, not market share.
What interconnectors connect the United States to its neighbours?: 16,568 MW of cross-border transfer capacity to Canada, Mexico, plus 4,400 MW planned. Capacities are from the Global Transmission Database (v1.0, 2023).

Elsewhere in the United States

Transmission lines Substations Power plants Data centres

Network geometry: OpenStreetMap (ODbL) © OpenStreetMap contributors, ingested and measured by OverWatts · derived 2026-07-26. Counts every mapped line of 220 kV and above; the map layer draws the ≥380 kV backbone only, so it shows less than is measured here.