Sources, definitions and limitations
The index is a calculation from public operational data. Its usefulness depends on showing exactly what has been measured.
Reviewed 2 November 2026 · Republic of Ireland
The source and permission to reuse it
Supported by EirGrid Group Data. Wind Energy Index uses EirGrid’s public Smart Grid Dashboard API, selecting ROI (Republic of Ireland), WIND_ACTUAL and SYSTEM_DEMAND. Northern Ireland and all-island figures are not mixed into this index. The JSON download includes the precise source URLs and fetch times.
The EirGrid Group Open Data Licence, checked on 2 November 2026, permits copying, adaptation and commercial or non-commercial reuse with attribution. Data is supplied without a warranty or guaranteed continuity. Attribution does not imply endorsement. The site uses its own design and no provider logos.
Power, energy and percentages
At a single timestamp, the ratio is 100 × wind MW ÷ demand MW. A complete reported day contains 96 paired quarter-hour intervals. We estimate each interval’s energy as MW × 0.25 hours, then sum to get MWh. A daily ratio divides the wind energy by demand energy for that same day. A seven- or thirty-day ratio uses the sum of complete-day energy totals, not the mean of daily percentages.
Dates and times are kept exactly as the source reports them, without local-time conversion. Fetch times explicitly use UTC. These are the source’s reported-day estimates, not independently reconciled settlement or civil-day statistics. The index does not adjust daylight-saving transitions. A day with repeated or missing quarter-hour labels is withheld from daily totals rather than silently repaired.
Output as a percentage of demand is not the same as the share of domestic generation, renewable electricity accounting, or a physical tracing of electricity to consumers. Imports, exports and the wider generation mix require additional context.
Completeness and freshness
Null, negative, non-numeric, implausible or unpaired readings are excluded. Duplicate readings reject a refresh. Daily totals require exactly the full set of quarter-hour labels. Missing days or intervals do not count as zero; incomplete periods have no aggregate ratio. Forecast values are never substituted.
The cPanel server refreshes on visits, at most once per 15 minutes for today, and once per reporting date for the preceding 30 days. One lock prevents overlapping refreshes. Failures are retried no more often than every five minutes. There is no background scheduled collector. An update delay appears when a successful fetch is older than one hour or the latest source reading is more than 90 minutes old. The last good dated snapshot stays visible.
The launch includes a real EirGrid snapshot fetched on 2 November 2026. It is a fallback, not synthetic data. If the public feed fails, the fallback does not become a new current reading. For critical decisions, use EirGrid’s official information.
Window extremes
The highest daily share is the maximum among complete days in the displayed historical window. The longest low-wind run counts consecutive observed quarter-hours with wind below 10% of demand. Missing intervals break a run; the observed duration may be only part of a longer event. This chosen threshold is not a weather definition of calm. Neither measure is an all-time record.
Editorial approach
Six explainers introduce the data and the electricity system using primary public sources. Review dates are shown on each page. Planned capacity, planning permission and operational generation are kept separate. This is an independent information project, not an official grid service.
Additional energy datasets
The homepage adds EirGrid large-scale solar, ROI interconnector flows and CO₂ intensity. Each series has its own source time. Solar excludes small-scale embedded generation; small negative readings are retained as published. Positive interconnector values mean imports from Great Britain; negative values mean exports. Moyle belongs to the Northern Ireland series and is not added to ROI.
The fuel contribution table covers the source’s last 24 hours. Source values are MWh, displayed as GWh. Net imports can be negative. It is not an instantaneous generation mix. EirGrid’s carbon measure excludes imported electricity’s overseas emissions; it is not a lifecycle or consumption-based footprint. See the Carbon Clock methodology.
The energy-data page uses SEAI National Energy Balance SEI01, CSO county consumption MEC03, CSO data-centre consumption MEC02 and Gas Networks Ireland’s public supply file. JSON-stat dimensions, units and values are checked before replacing a snapshot. Null stays unavailable. County and Dublin-district totals overlap and must not be added together. Data-centre percentages use metered consumption, not current grid demand.
As checked on 2 November 2026, SEI01 ends in 2024, while SEAI separately offers a 2025 spreadsheet. We retain the reproducible API series and show that difference. Primary energy by fuel is different from final energy by sector; ktoe is an energy unit, not a claim that the energy came from oil. Gas readings are daily but released quarterly; the retrieved file ends on 31 March 2026, and partial years are labelled.
Historical wind dispatch-down is a manually verified full-year Ireland series for 2016–2024 from EirGrid’s August 2025 historical table. The source’s partial 2025 total is excluded. It is a dated historical snapshot, with a link to newer reports. Dispatch-down is constraints plus curtailment as a share of available wind energy; it is not inferred from forecast errors.
Weather and the Wind Atlas
Met Éireann’s established hourly observations CSV supplies wind speed, gust, direction and temperature. It is provisional and not quality controlled. The CSV itself has no observation timestamp: fetch time is not substituted for observation time. A retained source-page report label is shown only for the matching seed snapshot. Missing gusts are not zero. Knots are converted to km/h by multiplying by 1.852.
The Wind Atlas uses SEAI’s published 50-metre modelled mean wind-speed polygons for 2001–2010. Bulk data modified 23 July 2021 was transformed from EPSG:2157 to geographic coordinates, simplified by 350 metres and sampled to an approximately 1–2 km display grid. Coordinates and map clicks inspect the same complete grid; filtering changes the display only. Null means outside source coverage, not calm wind. This derivative is not suitable for engineering or siting decisions.
Weather station reference coordinates come from Met Éireann station descriptions and its 2023 rainfall study. Coastline geography comes from © Tailte Éireann’s National 250k Map of Ireland, generalised for reference and not a legal boundary.
Refresh and licences
Grid context checks on visits at most every 15 minutes; weather at most every 30 minutes. SEAI/CSO JSON-stat series and gas supply are checked on visits at most daily. Each source has its own last-good cache and a five-minute retry floor. A source error preserves its dated snapshot rather than preventing other sources from loading. Older source coverage is always shown, even after a successful check.
Bulk map derivatives and the historical dispatch-down series are frozen dated releases, refreshed through the documented local build process. No scheduler was added. EirGrid data uses the EirGrid Group Open Data Licence. SEAI, CSO, Met Éireann, Gas Networks Ireland and Tailte Éireann examples use CC BY 4.0, with attribution and modifications stated. Met Éireann’s additional attribution and disclaimer appear on the weather page.