How the grid and market interact

All of us power our lives with electricity. SONI is responsible for  planning and operating the electricity grid in Northern Ireland. The grid is an intricate system of cables that transports electricity from where it is generated to where it is needed.

The electricity market is where generators and suppliers trade electricity. A lot of work happens behind the scenes to balance supply and demand. Market trading ensures that we have a safe, reliable and efficient electricity supply.

Since 2018, the I-SEM is the wholesale electricity market for Ireland and Northern Ireland. It brings together these two separate Transmission System Operators into an all-island arrangement. The wholesale electricity market is where electricity is bought and sold before being delivered to consumers. Its two main participants are generators and suppliers.

It aims to deliver:

Single Electricity Market Operator Power Exchange (SEMOpx) and Single Electricity Market Operator (SEMO) make up parts of the electricity market. They are overseen by the SEM Committee. This consists of the Commission for the Regulation of Utilities (CRU) in Dublin, the Utility Regulator (UR) in Belfast, plus an independent member and a deputy independent member.

Single Electricity Market Operator Power Exchange (SEMOpx) operates the day-ahead and intraday electricity markets for Ireland and Northern Ireland. There are the five ex-ante markets for trading energy.

The day-ahead market is a daily auction. It closes the day before the energy is delivered. The intraday market is closer to real time, with three auctions every day. There is also an intraday continuous market.

The Single Electricity Market Operator (SEMO) operates the balancing market which balances real-time supply and demand for electricity. The balancing market is a real-time imbalance market. Its primary function is to calculate costs to balance the system and to set the price of actions taken.

Interconnection with other countries also helps our power system to run efficiently. The island of Ireland is interconnected with Great Britain. This allows us to share power across our networks.