Quick facts — last updated 2026-06-25
- RoleTransmission System Operator
- OwnerEirGrid (since 2009)
- RegulatorUtility Regulator (NIAUR)
- Market it co-runsAll-island SEM (via SEMO)
- Owns the wires?No (NIE Networks does)
- Customer phone line?None (not consumer-facing)
Sources: SONI, EirGrid and the Utility Regulator.
Good to know
SONI is not who you call
SONI runs the grid behind the scenes and has no customer line for homes or businesses. For a power cut, fallen line or new connection, contact NIE Networks on 03457 643 643 (24 hours). If there is a danger to life, call 999.
What SONI does, and what it does not
SONI is the least visible company in the chain, and the most misunderstood. It never touches a wire or sends a bill, yet without it the grid would collapse within seconds. Here is the honest split.
SONI DOES
- +Balance supply and demand on the grid in real time, every second;
- +Tell power stations and wind farms when to run and how much to produce;
- +Keep the system stable (voltage and frequency within safe limits);
- +Co-run the all-island wholesale market with EirGrid, through SEMO;
- +Plan how the transmission grid should grow to connect more renewables.
SONI does NOT
- −Own the towers, lines or substations (NIE Networks owns them);
- −Generate electricity;
- −Sell electricity or send you a bill;
- −Fix power cuts or deal with homes and businesses directly;
- −Have a customer phone line for the public.
The part almost everyone gets wrong: the grid has no "off switch" buffer
Here is the non-obvious truth. Electricity cannot be stored cheaply at grid scale, so the amount being made and the amount being used must match exactly, all the time. If they drift apart for even a few seconds, the whole system can trip and the lights go out across the region. SONI's entire job is to stop that from happening. It is constantly nudging generators up and down to keep the balance, like someone balancing a tray of glasses on one hand while walking.
This is why a small region like Northern Ireland shares a market with the Republic of Ireland. On its own, the Northern Ireland grid is small, and small grids are hard to balance when a big wind farm suddenly drops or a large plant fails. By joining the all-island Single Electricity Market, the two systems back each other up, which keeps the lights on and prices lower than two separate small markets could manage. SONI and EirGrid run that shared system together.
Trace your electricity, step by step
Follow the journey of one unit of electricity from a wind farm to your kettle. Click each step to see exactly what SONI does (and where it steps back and lets NIE Networks take over).
You reached your home, and never once dealt with SONI.
That is the whole point: SONI works invisibly. For anything you actually need, the contact is your supplier (bills) or NIE Networks (power cuts).
The journey of electricity in Northern Ireland
| Stage | Owned or run by | What SONI does here |
|---|---|---|
| 1. Generation | Power stations and wind farms | SONI tells generators when to run and how much to produce, minute by minute, to match demand. |
| 2. Wholesale market | The all-island SEM (via SEMO) | SONI co-runs the Single Electricity Market with EirGrid, so the cheapest available power is used first across the whole island. |
| 3. Transmission grid | NIE Networks owns the towers | SONI operates these high-voltage lines in real time, controlling flows and keeping the system stable. This is its core job. |
| 4. Distribution network | NIE Networks | SONI hands the power to NIE Networks, which carries it through local poles and cables to your meter. SONI steps back here. |
| 5. Your home | You and your supplier | Your supplier bills you. You never deal with SONI at all. For a power cut you call NIE Networks. |
SONI vs NIE Networks: the two grid companies, side by side
Northern Ireland splits the grid job between two companies. One owns the hardware, the other runs the system. Mixing them up is the single most common error in this topic.
| Question | SONI | NIE Networks |
|---|---|---|
| Owns the wires and substations? | No | Yes |
| Runs the grid in real time? | Yes | No (operates distribution only) |
| Fixes your power cut? | No | Yes |
| Connects your new home? | No | Yes |
| Co-runs the all-island market? | Yes | No |
| Owned by | EirGrid | ESB Group |
| You contact them? | Never | For faults and connections |
How SONI shapes your bill without ever appearing on it
You will never find "SONI" as a line on your electricity bill, but it touches your price in two ways.
Transmission charges
SONI's running costs are recovered through transmission "use of system" charges, regulated by the Utility Regulator. These sit inside the network part of your bill, alongside the NIE Networks distribution charge.
The market order
By co-running the all-island market, SONI helps decide which generators are dispatched and in what order (cheapest first). That ordering sets the wholesale price, which is the biggest single chunk of your bill.
The insider point most guides miss
When you read "Northern Ireland prices went up", the instinct is to blame the supplier or NIE Networks. But the largest mover is usually the all-island wholesale price that SONI and EirGrid's market produces, driven mostly by gas and wind across the whole island. That is the structural trap: households focus their energy on the one part they can change (the supplier, about a fifth of the bill) while the half of the bill that is wholesale, set by an island-wide market, gets ignored because no one can switch it. Knowing this changes the question from "who do I blame" to "what part can I actually act on".
SONI: the Selectra expert answers your questions
SONI is the Transmission System Operator for Northern Ireland. It runs the high-voltage electricity grid in real time, second by second, making sure that the amount of power being generated always matches the amount being used. It tells power stations when to start and stop, keeps the system stable and plans how the grid should grow. It does not own the wires, generate electricity or sell it.
No. NIE Networks owns the physical wires, poles and substations and fixes power cuts. SONI operates the transmission grid in real time but owns none of it. A simple way to remember it: NIE Networks is the road builder and repair crew, SONI is the traffic controller deciding what flows where. For anything you can touch or report, the answer is NIE Networks, not SONI.
Call NIE Networks on 03457 643 643, 24 hours a day, or report online at powercheck.nienetworks.co.uk. You never contact SONI. SONI has no customer service line for households because it does not deal with homes or businesses directly, only with the wider grid.
SONI is owned by EirGrid, the Republic of Ireland's state-owned Transmission System Operator, and has been since 2009. To keep it fair, SONI is run with its own independent board and management, and it is licensed and regulated by the Northern Ireland Utility Regulator. It works alongside EirGrid to run the all-island electricity system.
Yes, indirectly. SONI's running costs are recovered through transmission charges, which form part of the network charge bundled into every bill. More importantly, by co-running the all-island Single Electricity Market, SONI helps decide which generators run and in what order, which shapes the wholesale price you ultimately pay. You never see a SONI line item, and you cannot switch away from it.