Ireland's Daytime Electricity Demand Falls Below Night-time for First Time on March 21

On March 21, Ireland's lowest daytime electricity demand fell below the night-time valley for the first time, primarily due to a significant increase in rooftop solar panels. Diarmaid Gillespie, EirGrid's director of system operations, noted that peak demand for the Republic is about 6GW, with a record of 6,024MW set on January 8, 2025.

Embedded solar significantly impacted demand, with early afternoon demand on Thursday, March 19, being almost 1GW less than the previous Thursday, attributed to more solar availability and better weather. Utility-scale solar also set new records, reaching 1,133MW on April 25. Gillespie stated that utility-scale solar has tripled in three years, now exceeding 1GW, enough to power almost 500,000 customers. Wind generation also hit a new high of 3,898MW on February 14 at 5:50 PM, with over 5GW of wind installed.

This progress, while welcome, presents challenges for EirGrid in balancing supply and demand. Intermittency is a key issue; wind is predictable, but solar is less so, with sudden drops due to clouds. Embedded solar, not directly connected to the grid, also poses a challenge as EirGrid cannot control its output. To address deficits, EirGrid typically uses open-cycle gas turbines but prefers battery energy storage, with 700-800MW already connected and more planned. Turlough Hill has provided storage for years, and more people are installing battery storage with solar.

Grid frequency and inertia are also critical. Traditional generators provide inertia through large rotating masses. Renewables lack this, so EirGrid uses synchronous condensers, with two installed at Moneypoint and Shannonbridge, to provide inertia and stabilize frequency. These measures allow the grid to accommodate up to 75% of electricity from renewables at any one time, known as the system non-synchronous penetration (SNSP) limit. This needs to increase to 95% to meet the government's target of 80% renewable electricity.