All-island dispatch-down of wind and solar rose from 7.7% and 4.2% in 2019 to 15.3% and 12.8% in 2026.
The T-4 capacity auction for 2029/30, held on 26 March 2026, cleared at €135k/MW.
Data centres use 23% of metered electricity in Ireland, and greater Dublin has been closed to new data centre connections since 2021.
Ireland targets 80% renewable electricity by 2030, including 9 GW of onshore wind, 5 GW of offshore wind and 8 GW of solar.
How the SEM works
How does the Irish electricity market work?
Ireland and Northern Ireland share one all-island wholesale market, the Single Electricity Market (SEM). EirGrid and SONI are the transmission system operators, SEMO runs the market and SEMOpx runs the power exchange. All trading is in half-hour periods, and since 1 January 2021 the day-ahead market has run as a local auction, without coupling to GB or the EU.
The SEM has lofty decarbonisation targets: 80% renewables by 2030, with 9 GW of onshore wind, 5 GW of offshore wind and 8 GW of solar. Renewable build-out combined with high-cost marginal generation has driven day-ahead spreads on a par with Ireland’s European neighbours.
Which markets can you trade power in in the SEM?
| Market | Order book closes | Delivery | Coupled with GB? |
|---|---|---|---|
01Day-ahead market (DAM) | 11:00 the day before | 23:00 to 23:00, 48 half-hour periods | No; a local SEM auction since 2021 |
02Intraday auction 1 (IDA-1) | 17:30 the day before | 23:00 to 23:00 | Yes |
03Intraday auction 2 (IDA-2) | 08:00 on the day | 11:00 to 23:00 | Yes |
04Intraday auction 3 (IDA-3) | 14:00 on the day | 17:00 to 23:00 | No; local SEM auction |
05Intraday continuous | Rolling, after the day-ahead market closes | Half-hour periods | n/a |
06Balancing market | Real time | Half-hour imbalance settlement | n/a |
How does the SEM compare with the GB electricity market?
| Feature | Ireland’s SEM | Great Britain |
|---|---|---|
| Area | Republic of Ireland and Northern Ireland | England, Scotland and Wales |
| Day-ahead market | Local half-hourly auction on SEMOpx | Hourly and half-hourly auctions on EPEX and N2EX |
| Ancillary services | DS3 System Services at regulated tariffs, moving to auctions under FASS | Dynamic Containment, Moderation, Regulation and Quick Reserve, bought competitively by NESO |
| Capacity market | T-4 and T-1 auctions; battery de-rating calibrated to an 8-hour loss of load window | T-4 and T-1 auctions; de-rating set by duration |
| Battery charging from co-located renewables | Not allowed for a battery that shares a renewable site’s connection (CRU, April 2026) | Allowed |
| Renewable support | RESS auctions, with top-up to the strike price for some rounds | Contracts for Difference |
Data centres
Can new data centres connect to the grid in Ireland?
Yes, but only with their own dispatchable capacity. Under the CRU’s December 2025 decision, new data centres over 10 MVA must build dispatchable generation or storage close to the site that covers 100% of their Maximum Import Capacity (MIC) on a de-rated basis, and can’t bring extra demand online until it’s in place. That capacity must be front-of-meter, separately metered and active in the capacity and wholesale markets.
Large data centres must also source at least 80% of their annual demand from new Irish renewable generation within six years of energisation. Meeting the requirements brings exemption from emergency curtailment.
What flexible demand connections are available in Ireland?
European law now obliges the regulator to make flexible arrangements available wherever capacity is short, so in Ireland the decision has largely been made for data centres.
| Arrangement | How it works | Notice before a reduction |
|---|---|---|
01Timed (scheduled) | ESB Networks offers agreements setting the hours, days or seasons when the site must stay below an agreed level | Known in advance |
02Flexible now, firm later | Ireland’s flexible demand connections let a site connect early under restrictions, then convert to firm once reinforcement is complete | Known in advance |
03Real-time curtailment | EirGrid’s operating protocol allows two minutes to acknowledge an instruction and five to comply, with no cap on hours and no compensation | Minutes |
04Bring your own generation | Mandatory for larger data centres under the December 2025 decision | n/a |
What is the Large Energy User Action Plan?
Ireland’s plan for ‘co-locating everything’. The Large Energy User Action Plan (LEAP) sets out a plan-led approach for large energy users such as data centres and semiconductor manufacturing, centred on green energy parks where onshore and offshore renewables, storage and flexible thermal plant sit together. Its 17 objectives cover system planning, a single point of contact for permitting, market design that rewards flexibility, flexible grid connections and private wire.
Modelled in Gridcog
How much battery storage does a data centre need to connect in Ireland?
Far more than the equivalent gas capacity. Using the latest T-4 de-rating factors, Gridcog Senior Energy Analyst Dan Lehmann sized the proximate capacity a 25 MVA data centre needs to meet the CRU’s 100% de-rated requirement.
Ireland’s de-rating method calibrates each asset against an 8-hour loss of load expectation standard, 2.7 times the equivalent GB window, which heavily penalises short-duration batteries. Projects built for proximate generation can still stack capacity revenue, but only on rolling one-year contracts rather than the standard 10 years. Battery developers will likely be able to contract with data centres on toll-like agreements as an alternative reliable revenue stream.
Dan LehmannSenior Energy Analyst
Capacity needed for a 25 MVA data centre
90 MW
Four-hour battery
29 MW
Gas turbine
Sizing storage for a data centre connection or a constrained wind farm in Ireland?
Model your project in GridcogBehind the meter
Does behind-the-meter solar pay in Ireland?
Better than the weather suggests. In Laura Hoffmann-Ostenhof’s model of a supermarket using 470 MWh a year, run across nine European markets on the latest 12 months of prices, Ireland came second for solar alone, with about €42,000 of annual bill savings from a 300 kW system, because daytime wholesale prices are consistently high. With a 500 kWh / 2-hour battery added, Ireland ranked close behind Portugal and Italy.
How Gridcog models the SEM
How does Gridcog model Ireland’s Single Electricity Market?
With SEM prices, capacity results and system services in one model, in half-hour periods. Gridcog co-optimises a battery’s dispatch across the markets it can access and shows how dispatch-down, connection limits and contracts change each stakeholder’s cashflows.
SEM day-ahead prices in the Gridcog Library, plus your own forward curves. Market Price Forecast Uncertainty lets a battery dispatch on a forecast and settle on actual prices.
DS3 payments modelled as regulated tariffs multiplied by the temporal scarcity scalar, using historic SNSP data for each period.
All historic T-4 and T-1 clearing prices for the all-island SEM, with asset-level de-rating factors by duration.
Share one export limit between a battery and a wind or solar farm, apply a Site Import Schedule for timed or phased demand connections, and upload interval data to represent real-time curtailment.
Network tariffs and non-commodity costs for Ireland, so behind-the-meter projects show their full bill savings.
Model RESS-style strike prices, tolls, floors and hybrid PPAs, add each stakeholder, and compare cashflows, IRR and NPV in the Investment Case Report.
Experts
Who are Gridcog’s Irish market experts?
Gridcog’s London team covers Ireland alongside GB and the rest of Europe.
Dan Lehmann
Senior Energy Analyst, London
Helps clients model energy markets in the UK and Europe, and wrote Gridcog’s analysis of Ireland’s co-location opportunity. Before Gridcog, he led the development of smart charging products for fleets at EO Charging.
Joshua Elliott
Energy Analyst
Author of Gridcog’s guide to flexible grid connections for data centres in GB and Ireland.
Pio Pius
Business Development Manager, London
Focused on bringing Gridcog to major clients across GB, Ireland and the Nordics.
Genna Boyle
CCO and Head of EMEA
Began her career in energy trading at Contact Energy in New Zealand, then helped set up the trading team at Limejump and went on to lead its commercial team.
Who models SEM projects in Gridcog?
Developers and IPPs, investors and funds, energy majors, data centres and large energy users, and consultants.
Request a live demo
Model your SEM project in Gridcog
Request a demo and we’ll show you how Gridcog models your project against SEM prices, DS3, the capacity market and Irish connection rules.
The team behind Gridcog
Fabian Le Gay Brereton
Chief Executive Officer & Co-Founder
Previously co-founded Greensense, acquired by ERM Power (now Shell Energy).
Pete Tickler
Chief Product Officer & Co-Founder
Co-founded Greensense and led digital innovation at ERM Power (now Shell Energy).
Genna Boyle
Chief Commercial Officer & Head of EMEA
More than 10 years in energy strategy, trading and renewables, with senior roles at Battery Optimiser and Limejump.
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