Negative-price exposure, curtailment, grid fees, support schemes — the framework behind Ireland's battery and PV economics. The same rules that drive our PV-Watcher and BESS-Optimizer.
Ireland's all-island I-SEM is one of the most wind-intensive grids in the world (very high curtailment, frequent negatives) — BESS economics rest on EirGrid/SONI System Services and the Capacity Market more than arbitrage, though DS3 revenues are falling as the system moves to auctions.
The I-SEM day-ahead market regularly produces negative prices as wind penetration rises (historically around 4% of half-hour periods, and growing). Under RESS 1, supported projects received no support payment in any period with a negative day-ahead price; RESS 3 softened this via 'Unrealised Available Energy Compensation' (UAEC), paying at the strike price for available energy not generated due to curtailment/oversupply, including negative-price hours.
Ireland uses 'dispatch-down' — curtailment (system-wide, e.g. the System Non-Synchronous Penetration limit, currently 75%, targeted toward 95% by 2030) plus constraints (local network). In 2025 the Republic's wind dispatch-down was 11.3% (4.7% curtailment + 6.6% constraints); constraint costs were roughly €567M in 2024/25. Firm generators are compensated up to their Firm Access Quantity (interim Art. 13 IEMR), while non-firm output (~18%) is generally uncompensated.
Standalone storage (Energy Storage Units) has had favourable treatment, paying only Demand TUoS rather than both generator and demand charges. The CRU's interim 'minded-to' decision moves ESUs to Generator TUoS instead, with the industry targeting the tariff year from 1 October 2026 — treat as proposed/interim, not settled.
SEM day-ahead and intraday energy, the Capacity Market (CRM), and System Services. DS3 services (e.g. Fast Frequency Response) were historically the most lucrative stream but effective rates have fallen 40%+ since 2022; DS3 is being replaced by the Future Arrangements for System Services (FASS) — a Day-Ahead System Services Auction (DASSA) — with regulated contracts extended to no later than 30 September 2027. The Dec 2024 CRM T-4 auction cleared near €150,000/MW for 2028/29, though de-rating for 1–2 hour systems has tightened.
Sources: SEM Committee — FASS Gap Decision Paper (DS3→DASSA) · EirGrid — Renewable Constraint & Curtailment Report 2024 (Apr 2025) · CRU — ESU TUoS treatment (D-TUoS→G-TUoS) · SEMO — Capacity Market overview · Pinsent Masons — RESS 3 / UAEC · Modo Energy — Ireland BESS in transition (2026)
Last reviewed 2026-06-03. Regulatory summary, no legal advice — verify against the primary source before investment decisions.
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