SP Transmission at a glance
Current figures — last updated 2026-06-25- Legal name
- SP Transmission plc (SPT)
- Part of
- SP Energy Networks · ScottishPower · Iberdrola
- Region
- Central and southern Scotland
- Voltages
- 132 kV, 275 kV, 400 kV
- Regulator
- Ofgem (RIIO-T3, 2026–2031)
- Runs the grid?
- No — NESO does (since 2024)
What SP Transmission owns
SP Transmission holds one of the three GB transmission licences. Its patch, central and southern Scotland, is the corridor that wind power from the north and from offshore must cross to reach the much bigger demand in England. That gives it a role out of proportion to its size.
The cross-border corridor
400 kV and 275 kV overhead lines and substations carrying power from the Scottish Highlands and the Central Belt down toward the boundary with England.
Subsea links to England
High-voltage direct-current cables under the North Sea, built jointly with National Grid (the Eastern Green Link projects), to move Scottish power south without flooding the overland grid.
Grid reinforcements
New and upgraded lines and substations across southern Scotland to raise how much power the corridor can carry, the direct fix for constraint costs.
Why "ScottishPower transmission" is confusing, untangled
The ScottishPower name covers several very different jobs, and people mix them up constantly. Here is the family tree, simplest at the bottom.
| Name | What it is | Can you switch it? |
|---|---|---|
| Iberdrola | Spanish-headquartered parent group. | No |
| ScottishPower | The UK brand under Iberdrola. | No |
| SP Energy Networks | The regulated networks arm (transmission + distribution). | No |
| SP Transmission | High-voltage owner, southern Scotland (this page). | No |
| ScottishPower (supply) | The household energy supplier. | Yes |
The takeaway: everything above the bottom row is a monopoly you cannot change. Only the supplier at the bottom is switchable, and being a ScottishPower network customer does not tie you to ScottishPower as a supplier.
Who do I actually call? Quick check
For a household problem in southern Scotland, SP Transmission is almost never the answer. Pick your situation; the answer is also in the table below.
| Situation | SP Transmission? | Distribution (105) | Supplier |
|---|---|---|---|
| Power cut on your street | No | Yes | No |
| Downed wire / danger | No | Yes + 999 | No |
| Bill, tariff, meter | No | No | Yes |
| New home connection / EV charger | No | Yes | No |
| Connect a wind farm / large load | Yes | No | No |
The insider point: SP Transmission owns the most valuable bottleneck in Britain
SP Transmission is a regulated monopoly; Ofgem caps its revenue under RIIO-T3 (2026–2031) and suppliers pass the cost into your bill. But its strategic weight is bigger than its share of the network.
Almost all of Britain's cheap wind sits north of SP Transmission's patch. To reach England, that power must pass through southern Scotland, across the grid SP Transmission owns. When that corridor is full, the wind is switched off. In 2025, 98% of Britain's curtailed wind was in Scotland, and the country paid roughly £1.46 billion to switch wind off and gas on.
So the subsea links and reinforcements SP Transmission is building are not vanity projects, they are the direct cure for a bill that could otherwise climb toward £8 billion a year by 2030. Widening this one corridor is one of the highest-value investments on the entire grid.
SP Transmission: frequently asked questions
SP Transmission is the company that owns and maintains the high-voltage transmission network in southern and central Scotland: the pylons and 275 kV and 400 kV lines that carry bulk power. It is part of SP Energy Networks (ScottishPower / Iberdrola). It does not sell electricity to homes and does not fix household power cuts.
They are related but different. SP Energy Networks is the umbrella that runs the regulated networks; it includes SP Transmission (the high-voltage owner in southern Scotland) and two distribution networks (SP Distribution in central and southern Scotland, and SP Manweb in Merseyside, Cheshire and North Wales). ScottishPower is the wider brand, and the household energy supplier is a separate ScottishPower business. All sit under Iberdrola.
No. Call 105, free, 24/7. In central and southern Scotland it routes you to SP Energy Networks' distribution business, which owns the local cables and fixes faults. SP Transmission owns the high-voltage backbone, not your household supply. If a line is down or there is danger, also call 999.
SP Transmission is owned, through SP Energy Networks and ScottishPower, by Iberdrola, a large Spanish-headquartered energy group. So unlike National Grid (a UK-listed company) and SSEN Transmission (part of SSE), the high-voltage grid of southern Scotland sits under foreign ownership, while still being a regulated UK monopoly overseen by Ofgem.
Because Scottish wind has to travel through southern Scotland to reach England. SP Transmission owns that stretch of grid. When it is too weak to carry the power, the wind is switched off and English gas is switched on, at a cost of around £1.5 billion a year to bills across Britain. SP Transmission's big projects, such as new subsea links to England, are built to relieve exactly that.