Idaho has 1,271 high-voltage and bulk transmission line segments totalling roughly 10,811 miles, operated by 18 distinct utilities and federal agencies across the Western Interconnection (WECC market). Of that total, 2,009 miles are extra-high-voltage (345 kV and above) — the long-distance backbone that moves power across the state.
The interactive map below shows every transmission segment in Idaho from the HIFLD/CISA US Electric Power Transmission Lines dataset, colour-coded by voltage class. Click any line for the operating utility, voltage, status, and the substations it connects. Or browse the national US transmission map to compare Idaho to every other state.
Idaho Electric Transmission Network by the Numbers
- 1,271 total transmission line segments covering ~10,811 miles (HIFLD/CISA dataset)
- 2,009 miles of extra-high-voltage transmission (345 kV and above) — the long-distance backbone
- 18 distinct operators own or operate transmission infrastructure in the state
- Voltage profile: 512 miles of 500 kV plus 1,497 miles of 345 kV
- Grid context: part of the Western Interconnection, balanced through WECC
- 492 of the segments (about 2,559 miles) are flagged as inferred in the source dataset — routing was estimated rather than digitised from authoritative source data
Voltage Class Breakdown for Idaho
Every transmission segment in the dataset is tagged with a voltage class. Here is how Idaho’s 10,811 miles of line break down:
| Voltage class | Miles | Segments | Share |
|---|---|---|---|
| 500 kV | 512 | 7 | 4.7% |
| 345 kV | 1,497 | 19 | 13.8% |
| 220 – 287 kV | 2,788 | 119 | 25.8% |
| 100 – 161 kV | 3,668 | 609 | 33.9% |
| Under 100 kV | 2,346 | 510 | 21.7% |
Top Transmission Operators in Idaho
Idaho Power is the largest transmission operator in Idaho with 4,728 miles of line — about 43.7% of the state total. The top four operators (Idaho Power, Pacificorp, Bonneville Power Administration, Avista) control about 88.3% of Idaho’s transmission mileage between them.
| Rank | Operator | Line miles | Share |
|---|---|---|---|
| 1 | Idaho Power | 4,728 | 43.7% |
| 2 | Pacificorp | 2,750 | 25.4% |
| 3 | Bonneville Power Administration | 1,207 | 11.2% |
| 4 | Avista | 858 | 7.9% |
| 5 | Northwestern Energy Llc – (Mt) | 179 | 1.7% |
| 6 | Raft River Rural Elec Coop | 147 | 1.4% |
| 7 | Salmon River Electric Coop | 111 | 1.0% |
| 8 | Idaho County L&P Coop Assn | 108 | 1.0% |
| 9 | Fall River Rural Elec Coop | 106 | 1.0% |
| 10 | Northern Lights | 99 | 0.9% |
Most-Connected Substations in Idaho
These substations have the highest number of incoming and outgoing transmission line connections in the HIFLD dataset — effectively the busiest hubs in the Idaho grid.
| Rank | Substation | Line connections |
|---|---|---|
| 1 | Goshen | 20 |
| 2 | Boise Bench | 17 |
| 3 | Brownlee | 15 |
| 4 | Midpoint | 11 |
| 5 | North Lewiston | 11 |
| 6 | Caldwell | 10 |
| 7 | Rathdrum | 10 |
| 8 | Grace | 10 |
| 9 | Unknown201591 | 9 |
| 10 | Unknown201292 | 9 |
Idaho’s Longest 500 kV and HVDC Corridors
These are the longest individual EHV (extra-high-voltage) and HVDC line segments in Idaho — the inter-regional transmission spine of the state.
| Corridor | Owner | Voltage | Miles |
|---|---|---|---|
| Hemingway — Burns | Pacificorp | 500 kV | 131 |
| Hemingway — Midpoint (500Kv) | Pacificorp | 500 kV | 130 |
| Bell — Taft | Bonneville Power Administration | 500 kV | 96 |
| Dworshak — Taft | Bonneville Power Administration | 500 kV | 90 |
| Lower Granite — Hatwai | Bonneville Power Administration | 500 kV | 33 |
| Dworshak — Hatwai | Bonneville Power Administration | 500 kV | 29 |
Data Sources and Caveats
Transmission line geometry and attributes come from the HIFLD/CISA US Electric Power Transmission Lines public dataset. Per-state stats on this page are computed by intersecting that dataset with the Idaho state polygon (Esri USA States Generalized Boundaries) and summing the intersected segments using haversine distance on the source line geometries. The dataset only covers transmission infrastructure (typically >= 35 kV); residential distribution wiring is not included. Some segments crossing the state boundary appear in both states’ totals.
Compare Idaho to Other States
Use the national US transmission lines map to compare Idaho’s grid to every other state — including total mileage, operator concentration, and EHV backbone share.
