Ancillary Services & Other System Charges

Costs and charges for services to securely operate and restore the electricity system.

‌Ancillary Services & Other System Charges

Certain payments and charges are paid or levied outside the Single Electricity Market by the Transmission System Operators, EirGrid and SONI.

Most of these are related to ancillary services costs for services necessary for the secure operation and restoration of the electricity system. There are also other system charges which are intended to incentivise optimum performance of generators connected to ensure efficient use of the power system.

There are harmonised all-island arrangements for these payments and charges.

For any ancillary services settlement and billing queries please email CAS@eirgrid.com.

DS3 System Services

Search our Publications for related consultation documents and statements of payments and charges.

Transmission Use of System Charges (TUoS)

The system of charging for transporting power in bulk across the power system is the Transmission Use of System Charge (TUoS). TUoS charges are separate from the cost paid by customers for buying energy from a supplier or generator.

It applies to:

  • Generators on an all-island basis
  • Demand customers in Ireland (larger commercial or business users of electricity)
  • Suppliers in Northern Ireland
  • Distribution system customers who rely upon the transmission system 

The transmission system is the high voltage grid which brings bulk power to all regions of Ireland. It is the backbone of the power system, with interconnection to the lower voltage distribution system. TUoS tariffs are designed to recover the costs to operate, maintain and develop the transmission system.

The transmission tariffs recover the TUoS revenue from transmission users in a transparent way. This includes generators and large energy users connected directly to the transmission system or indirectly via the lower voltage distribution system.

TUoS Tarrifs

The Transmission Use of System (TUoS) charge comprises two parts: 

  • Network charges for using the transmission system infrastructure to transport electricity
  • System services charges for the costs arising from the operation and security of the transmission system

The following are the categories of tariffs in Ireland and Northern Ireland:


  • Demand tariffs - Commercial or larger users of power
  • Generator tariffs - Power stations or wind farms
  • Autoproducer - Customers who mainly produce power for their own use but may also export surplus power

Northern Ireland

  • Supplier tariffs - Tariffs for the current 8 suppliers in NI, based on time of year
  • Generator tariffs - Power stations or wind farms

Approved 2022/23 TUoS Tariffs

These tariffs have been developed on an all island basis but this statement of charges document is given for the Republic of Ireland.


MIC Administration Paper

The MIC Administration Paper outlines the policy for dealing with requested MIC changes for customers connected to the transmission system receiving transmission service via the DTS-T tariff schedule i.e. Directly Connected Transmission Demand Customers.

It is important that applicants applying for a demand connection accurately determines and specifies the MIC required. System reinforcements will be designed to facilitate this MIC. If the MIC is changed during construction or after connection work is completed a minimum notice period applies.

Billing and Metering

In EirGrid, Settlement provides data feeds to SEMO. We are responsible, in our role as Transmission Meter Operator, for providing meter data for all transmission connected Generating and Interconnector units.

Since 1 November 2007, this Meter Data is transmitted as per Market Settlement requirements and timelines. Dispatch instructions and Availabilities profiles are validated along with the Metered output before submitting to SEMO. In conjunction with this we conduct remote and manual on-site checks on all polled meters annually.  

A key role for Settlement is the invoicing and payments associated with a range of other transmission and market related services including: 

  • Transmission Use of System
  • Ancillary Services/DS3 System Services

These services are essential to the operation of the market and power system. They cover the collection of charges for usage of the Transmission System and securing the provision of Ancillary Services, such as operating reserve.