Where Ireland's Spare Grid Capacity Is

ESB Networks publishes a heatmap of its substations and how much spare capacity each one has for new generation. It answers a question about substations.

A solar or battery developer is asking a different question: which fields could use that capacity? To answer it you need the substations, every field in the State, the flood maps, the designated sites and the building outlines, all at once. No free viewer joins them, so we did.

What this is based on

• ESB Networks' availability capacity heatmap, as compiled on 12 December 2025. We counted the medium-voltage, 38 kV and 110 kV substations, the ones a generation project connects to.
• Every Land Registry title in the State: 3,217,764 freehold and leasehold titles from Tailte Éireann.
• A field counts here if it is 2 hectares or more, within 2 km of a substation with at least 5 MW of spare generation capacity, clear of mapped flood extents and designated sites (SAC, SPA, NHA and proposed NHA), has buildings on under 2.5% of its land, and is not already a solar farm (mapped in OpenStreetMap, or with a solar farm planning application inside it).

That gives 13,791 fields covering 113,454 hectares.

Counted on 22 September 2026. The same search in Precedent now returns fewer fields (13,436 on 28 September): we moved ESB's substations to their mapped positions, and the search now lists freehold titles only. The figures below are the 22 September count.

The headline: most of the capacity is not where the fields are

453 medium- and high-voltage substations show spare generation capacity. 310 have at least 5 MW of it that is usable. Dublin has 117 of those, more than a third.

Cork has the most qualifying fields, and Carlow has none at all.

County	Substations with 5 MW+ spare	Fields	Hectares
Cork	43	1,801	18,263
Dublin	117	1,708	13,289
Mayo	13	1,115	6,693
Galway	17	994	6,183
Kerry	13	762	7,649
Cavan	5	657	4,334
Meath	6	588	5,236
Tipperary	8	570	5,364
Sligo	6	561	3,672
Kildare	8	558	6,950
Clare	8	498	4,033
Wexford	7	468	3,884
Roscommon	5	457	2,400
Laois	5	452	3,530
Offaly	4	409	2,765
Longford	4	369	3,098
Limerick	10	316	1,858
Kilkenny	6	304	3,122
Wicklow	6	243	2,291
Leitrim	2	233	1,671
Westmeath	2	215	1,594
Louth	5	184	1,048
Waterford	4	139	1,149
Donegal	2	104	2,853
Monaghan	1	85	518
Carlow	0	0	0

Substations are counted in the county they stand in; fields are counted in their own county, so a field can qualify on a substation across the border. Three substations fall outside every council boundary, and one field has no county on the Land Registry, which is why the columns sum to 307 and 13,790.

Three things that stand out

1. A number on a map is not always capacity you can use. 31 of the 453 substations showing spare generation capacity are constrained further up the network, so that headroom cannot actually be reached. 19 of them show 5 MW or more. Kildare has five of those and Kerry four. We leave all of them out.

2. Carlow has no qualifying land at this threshold. No substation in the county shows 5 MW of usable spare generation capacity, and no Carlow field is within 2 km of one across the county line. At a lower threshold or a longer distance, the answer changes.

3. The biggest county for land is not the biggest county for substations. Dublin has almost three times as many qualifying substations as Cork, but fewer qualifying fields. Substations cluster where demand is; open land does not.

What this does not tell you

• It is not a connection offer. The heatmap is ESB Networks' indication of headroom. Only a connection application tells you what a site can connect, and on what terms. It also says nothing about projects already queued for the same capacity.
• 38 kV and 110 kV substation positions are indicative. Against OpenStreetMap's mapping of the same stations they sit a median of about 800 m out, which is why we use a 2 km radius rather than a tight one.
• A database cannot tell a field from forestry. In a photo check of 100 random fields with few or no buildings on them, 70 were open land. Most of the rest were forestry, road verges and strips of land around housing estates. Look at the imagery before acting on a field.
• The heatmap changes. ESB republish it quarterly, and capacity is taken up as projects connect.

A note on method

Each field's distance was measured from its boundary to the substation, in PostGIS, and the largest usable headroom within 500 m, 1 km, 2 km and 5 km was stored for every title of half a hectare or more. Flood extents are the OPW's mapping. Designated sites are the National Parks and Wildlife Service's. Building footprints are Tailte Éireann's; a building counts toward a field only when at least half of it is inside the boundary. "Usable" means the substation's headroom is not constrained further up the network, as ESB mark it.

Where Precedent fits

This post is one search, run once. In Precedent you run it yourself, today, for any county:

• Choose the headroom, distance and field size, for solar or for battery sites, and get the list of fields. (Grid capacity)
• Add the rest of the checks: flood, designated sites, existing solar, buildings on the land and slope. (Fields & farmland)
• Open a field to see its Land Registry title, the substations behind the match and farmland prices for the region.

It shows ESB's published heatmap, not a connection offer, and it can't tell a field from forestry, so look at the imagery before acting on a field.