Maine has 371 high-voltage and bulk transmission line segments totalling roughly 3,221 miles, operated by 3 distinct utilities and federal agencies across the Eastern Interconnection (ISO-NE market). Of that total, 848 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 Maine 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 Maine to every other state.
Maine Electric Transmission Network by the Numbers
- 371 total transmission line segments covering ~3,221 miles (HIFLD/CISA dataset)
- 848 miles of extra-high-voltage transmission (345 kV and above) — the long-distance backbone
- 3 distinct operators own or operate transmission infrastructure in the state
- Voltage profile: 848 miles of 345 kV but no 500 kV
- Grid context: part of the Eastern Interconnection, balanced through ISO-NE
- 295 of the segments (about 2,582 miles) are flagged as inferred in the source dataset — routing was estimated rather than digitised from authoritative source data
Voltage Class Breakdown for Maine
Every transmission segment in the dataset is tagged with a voltage class. Here is how Maine’s 3,221 miles of line break down:
| Voltage class | Miles | Segments | Share |
|---|---|---|---|
| 345 kV | 848 | 26 | 26.3% |
| 100 – 161 kV | 1,594 | 194 | 49.5% |
| Under 100 kV | 459 | 88 | 14.3% |
| Voltage not reported | 320 | 63 | 9.9% |
Top Transmission Operators in Maine
Central Maine Power is the largest transmission operator in Maine with 1,631 miles of line — about 50.6% of the state total. The top four operators (Central Maine Power, Emera Maine, Public Service Co Of Nh) control about 76.3% of Maine’s transmission mileage between them.
| Rank | Operator | Line miles | Share |
|---|---|---|---|
| 1 | Central Maine Power | 1,631 | 50.6% |
| 2 | Emera Maine | 814 | 25.3% |
| 3 | Public Service Co Of Nh | 14 | 0.4% |
Most-Connected Substations in Maine
These substations have the highest number of incoming and outgoing transmission line connections in the HIFLD dataset — effectively the busiest hubs in the Maine grid.
| Rank | Substation | Line connections |
|---|---|---|
| 1 | Surrowiec | 13 |
| 2 | Orrington | 11 |
| 3 | Coopers Mills | 11 |
| 4 | Larrabee Road | 10 |
| 5 | Wyman Hydro | 8 |
| 6 | Maguire Road | 8 |
| 7 | South Gorham | 8 |
| 8 | Unknown133132 | 7 |
| 9 | Louden | 7 |
| 10 | Graham | 7 |
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 Maine 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 Maine to Other States
Use the national US transmission lines map to compare Maine’s grid to every other state — including total mileage, operator concentration, and EHV backbone share.
