EirGrid's MPID345 would make Irish data centers grid stability actors

Data centers and new technology loads drew roughly 24 percent of Ireland's electricity in 2024, and that share is forecast to reach 30 percent by 2032. Against that backdrop, grid operator EirGrid has proposed a grid code modification, MPID345, that would for the first time impose generation-grade stability obligations on large demand facilities — data centers included.

The proposal reflects a hard commercial reality already visible in fault data. During a January 2022 fault, Ireland's data centers cut demand by 74MW, equal to 16 percent of total data center demand. By May 2025 the recorded reduction had climbed to 387MW, or 52 percent. When major loads react simultaneously, the resulting power imbalance can worsen frequency instability across the grid.

What does MPID345 require?

The modification introduces three linked technical requirements:

• Fault ride-through: facilities must remain electrically connected to the transmission system during voltage disturbances.
• Active power recovery: facilities must restore at least 90 percent of pre-fault demand within 500 milliseconds after voltage recovers to 0.9 per unit.
• Rate of change of frequency robustness: facilities must withstand frequency changes of up to plus or minus one hertz per second without disconnecting.

Requirements of this kind have historically applied to generation assets — wind and solar farms, high-voltage direct current (HVDC) interconnectors, and battery storage systems. Large electricity users faced looser standards because their individual system effect was smaller and their behavior more varied. That distinction is eroding as data center demand grows.

If adopted, MPID345 would mark a fundamental shift. Large demand facilities would behave as active participants in grid stability rather than simple consumers of electricity.

Where is compliance measured?

At the grid connection point, not asset by asset. IT load, UPS systems, cooling equipment, variable-speed drives, generators, transformers, storage, reactive-power equipment, protection systems and control logic all shape the active and reactive power profile the network sees during a disturbance. What matters is how these systems perform together through the fault, transfer and recovery sequence.

This exposes a gap in conventional data center design. A UPS may keep IT equipment online while its grid-side rectifier limits current, reduces input power, or disconnects during a disturbance. From the operator's internal view, the facility remains online. From the grid's perspective, the facility has stepped away from the system.

Operators should establish their site's actual voltage ride-through capability, rectifier current limits, protection thresholds, battery capability, generator transfer behavior and input-power recovery profile. Revised controls or protection settings may improve performance in some facilities. Software changes alone cannot overcome fundamental current, thermal or hardware constraints.

Is recovery the hard part?

Active power recovery is likely the most demanding element. Restoring 90 percent of pre-fault demand within 500 milliseconds requires coordinated behavior across the whole site.

UPS systems may recover at different rates. Mechanical systems may be restarting. Generators may be transferring. Batteries may be recharging. Protection timers may still be resetting. The demand profile seen by the grid is the combined effect of all these processes.

MPID345 is therefore not simply an energy question. It is a sub-second power orchestration challenge. The first question is not how much energy a facility needs, but how much active and reactive power is required, how quickly it must be delivered, and for how long.

There is no single route to compliance. Some sites may close part of the gap through UPS control and protection setting changes. Others may need fast-response power support, reactive-power capability, controllable noncritical loads, or changes to the wider electrical architecture. Each approach should follow a site-level assessment supported by detailed modeling using actual network, load, protection and OEM equipment data.

Recovery does not end when pre-fault demand returns. Batteries and other reserves must recharge without creating a second power step that could destabilize the grid, making controlled, ramp-limited recharge part of a credible grid-support strategy.

Ireland may be among the first markets to formalize these expectations for large demand, but it will not be the last. As electricity systems add more renewable generation and large digital loads, operators that treat energy resilience as a whole-site engineering challenge will be best placed to meet emerging requirements while protecting uptime, managing cost and supporting long-term decarbonization.