‌Ancillary Services & Other System Charges

A number of 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. On the 1 February 2010, harmonised all-island arrangements were brought into operation for both ancillary services and other system charges.

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

  • Find the Other System Charges 2022/23 Recommendations Paper here.
  • Find the Other System Charges 2021/22 Recommendations Paper here.
  • Find the Other System Charges Consultation Paper 2020/2021 here.
  • Find the Ancillary Services & Other System Charges reports for 2022/2023 here .
  • Find the Other System Charges Trip Report 2022/2023 here.
  • An information note on Harmonised Ancillary Services - 12 April 2016 can be found here.
  • Find the 2019/2020 Ancillary Services Statement of Payments and Charges here.
  • Find the 2020/2021 Ancillary Services Statement of Payments and Charges here.
  • Find the 2018/2019 Harmonised Other System Charges consultation paper here.
  • Find the 2018/2019 Harmonised Other System Charges methodology statement here.
  • Please find here the Other System Charges 2019/20 Recommendations Paper.
  • Find the DS3 System Services Enduring Arrangements Statement of Payments 2018 here.
  • Find the DS3 System Services Statement of Payments 2022 here.

Search our library for related consultation documents, statements of payments and charges and further related information.

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). It applies to Generators on an all-island basis, Demand Customers in Ireland (larger commercial or business users of electricity), and Suppliers in Northern Ireland. It is also paid by distribution system customers who rely upon the transmission system. TUoS charges are separate from the cost paid by customers for buying energy from a supplier or generator.

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 total costs involved in operating, maintaining and developing the transmission system. The transmission tariffs have been designed to fully recover the TUoS revenue requirement from transmission users in a transparent way. This includes both generators and large energy users connected directly to the transmission system or indirectly via the lower voltage distribution system. The following are the categories of tariffs:


  • 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

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

(a) Network Charges: for the use of the transmission system infrastructure for the transportation of electricity.

(b) System Services Charges: the costs arising from the operation and security of the transmission system.

Transmission Use of System charges are grouped into three tariff categories:

For further details on these charges please refer to the latest ‘Statement of Charges’ section.

Approved 2021/22 TUoS Tariffs

EirGrid has published on the 1 September 2021, the approved EirGrid Statement of Charges for ROI TUoS (Transmission Use of System) for the 2021/2022 tariff year. This includes the GTUoS (Generator Transmission Use of System) Tariffs. Please see below:

2019 - 2020 Statement of Charges

2020 - 2021 Statement of Charges

2021 - 2022 Statement of Charges

2022 - 2023 Statement of Charges

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

You can access a list of FAQs about the above document here.

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 extremely important that an applicant 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.

For more information please refer to the Updated MIC paper April 2015.  


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.