What is the ESB Networks capacity heatmap?
ESB Networks runs the distribution system, up to 110 kV (Distribution Code v8.0). Its heatmap gives, for each substation, the spare transformer capacity it estimates for new demand ("Demand Available MVA") and for new generation. The download we use is labelled 2026-07, compiled 12 December 2025. Demand calculation incorporates demand contracts and offers up to end Aug 2025.
EirGrid runs the higher-voltage transmission system. Its capacity is not on this map, and that is where large data centres connect. So the heatmap answers a narrower question: where could a smaller load, or a site's own supply, fit on the local network?
Dublin against the rest of Ireland
| Station class | Dublin: stations | Dublin: MVA | Dublin: none spare | Rest: stations | Rest: MVA | Rest: none spare |
|---|---|---|---|---|---|---|
| 110 kV | 6 | 606 | 33% | 0 | 0 | — |
| 38 kV | 16 | 233 | 50% | 97 | 2,142 | 18% |
| MV | 104 | 365 | 58% | 434 | 1,230 | 46% |
Dublin = the four Dublin council areas. "None spare" = share of stations showing no demand headroom. Totals overlap where stations share a parent, so they are an upper bound.
At 38 kV, 50% of Dublin's 16 stations show no headroom, against 18% elsewhere. At the smallest (LV) substations the figures are 67% and 55%.
Dublin is not uniformly red. ESB's own 220/110 kV transformers there show 606 MVA, led by Carrickmines (349 MVA), Inchicore T2102/T2104 (113 MVA), Finglas T2103/T2104 (87 MVA). Whether a large site could use it depends on the transmission system behind it, which EirGrid describes as fully constrained in Dublin.
Around today's data centres
For 13 of the 62 operating or under-construction campuses, no ESB station within 5 km shows any demand headroom. That fits where the campuses are: mostly in Dublin, where the local network is fullest. The station nearest a campus is usually a small MV substation (59 of 62), which says little about a campus that connects at 110 kV or above, and a full station beside a campus may be full because of the campus itself.
Where the room is outside Dublin
Outside Dublin, 59 transformer groups show at least 10 MVA of demand headroom at 38 kV. 14 of them (369 MVA in total) are within 10 km of a 220 kV or 400 kV substation (OpenStreetMap), among them Trien T143 (Kerry), Cordal (Kerry), Arklow (Wicklow). The ten largest figures outside Dublin (a station with several transformer groups can appear more than once):
| Station | Council | Demand headroom, MVA | Nearest 220/400 kV substation | km |
|---|---|---|---|---|
| Binbane T141/T142 | Donegal | 66.6 | Srananagh 220kV Substation | 61.3 |
| Thornsberry | Offaly | 65.1 | Castlelost 220 kV Substation | 15.2 |
| Dalton T141 | Mayo | 56.5 | Cashla 220 kV Substation | 46.1 |
| Reamore T142 | Kerry | 56.5 | Knockanure 220kV Substation | 19.4 |
| Lisheen | Tipperary | 56.4 | Kellis 220kV Substation | 57.7 |
| Booltiagh T143 | Clare | 56.4 | Prospect 220kV Substation | 14.2 |
| Binbane T143 | Donegal | 56.3 | Srananagh 220kV Substation | 61.3 |
| Cauteen T142 | Tipperary | 56.2 | Killonan 220kV Substation | 27.4 |
| Glenlara T141 | Cork County | 56.1 | Ballynahulla 220kV Substation | 16.7 |
| Glenree | Mayo | 56 | Srananagh 220kV Substation | 40.9 |
By council, the largest 38 kV totals outside Dublin are:
| Council | 38 kV stations | With none spare | 38 kV headroom, MVA | Largest single station |
|---|---|---|---|---|
| Cork County | 14 | 2 | 365 | Glenlara T141 (56.1 MVA, 38 kV) |
| Kerry | 9 | 1 | 323 | Reamore T142 (56.5 MVA, 38 kV) |
| Tipperary | 11 | 1 | 289 | Lisheen (56.4 MVA, 38 kV) |
| Mayo | 8 | 1 | 237 | Dalton T141 (56.5 MVA, 38 kV) |
| Donegal | 7 | 0 | 182 | Binbane T141/T142 (66.6 MVA, 38 kV) |
| Clare | 6 | 2 | 126 | Booltiagh T143 (56.4 MVA, 38 kV) |
| Wicklow | 3 | 0 | 74 | Arklow (53.6 MVA, 38 kV) |
| Offaly | 2 | 0 | 72 | Thornsberry (65.1 MVA, 38 kV) |
Council and station totals are upper bounds: stations that share a parent share its limit, and one connection can't exceed a single transformer.
Why it is not the whole picture
- Station capacity as of Oct 2025; demand contracts and offers to end Aug 2025; generation to early Oct 2025; compiled 12/12/2025. ESB labels the download '2026-07' and aims to update quarterly.
- Summing headroom across stations overstates what is usable: child stations share their parent's limit, so council and 5 km totals are an upper bound, not additive capacity.
- HV substation locations are indicative (ESB); MV/LV locations are exact. Council = statutory boundary containing the indicated point.
- Large data centres connect to the transmission system (EirGrid), whose capacity this map does not show. The heatmap covers ESB Networks' distribution stations, including ESB-owned 220/110 kV transformers in Dublin.
For scale: the largest campus by grid draw, Microsoft Grange Castle, averaged 155 MW in 2025 (EPA annual environmental report). The biggest single 38 kV station figure outside Dublin is 66.6 MVA, and the median 38 kV station there shows 13.7 MVA.
Grid capacity held by data centres, against what they actually draw
Data centres drew an average of 875 MW in 2025 but hold contracts for about 1.9 GW (2.3 GW counting other new loads): only 38–46% is in use. On paper that leaves room to grow under contracts signed before the 2021 rules, but the grid's 900 MW load-rejection limit and the MPID 345 caps now restrict how much more sites that can't ride through faults may draw.
Energy (GWh in a year) becomes average power (MW) by dividing by the hours in that year: 7,662 GWh ÷ 8,760 = 875 MW. The grey bars are grid capacity EirGrid reports as contracted to data centres, converted from MVA to MW at a power factor of 0.95. The gap between the red line and the end of the grey bar is capacity already promised to existing operators but not yet used; on paper even EirGrid's 14.6 TWh forecast for 2034 (about 1,667 MW on average) fits inside it, though for sites that can't ride through faults the grid's stability limit now binds before their contracts do. On top of this, the system operators' market sounding found about 5.8 GW of possible new data-centre demand. Big sites with EPA licences measured 776 MW of that draw themselves; peaks are higher than averages.
EstimateMVA-to-MW conversion, utilisation and unused headroom are StackPath estimates (3 Oct 2026); the 2034 average is EirGrid's TWh forecast divided by 8,760 hours.
Sources: CSO MEC02, 7 Jul 2026 · EirGrid All-Island Resource Adequacy Assessment 2026–2035, Dec 2025 · EirGrid Constrained Area Overview, May 2026 · EirGrid forecast as cited in CRU2025236, 12 Dec 2025 · EPA annual environmental reports, 3 Oct 2026
Why it matters
Our reading. Spare local capacity is mostly outside Dublin, in rural 38 kV stations sized for tens of megawatts. That suits smaller loads and on-site supply more than a hyperscale campus, which still needs a transmission connection from EirGrid. The heatmap shows where the distribution network has room; it does not show where a data centre could connect.