How much water do data centres use in Ireland?
| Year | Litres | Share of public supply | Basis |
|---|---|---|---|
| ~2021 | 810 million | 0.13% | Uisce Éireann public supply to all known data centres (Government Statement on the Role of Data Centres, 2022) |
| 2023 | 217 million | 0.036% | Sum of EPA AER public-supply water, 14 licensed data-centre installations (13 part-year) |
| 2024 | 752 million | 0.124% | Sum of EPA AER public-supply water, 15 licensed data-centre installations (1 part-year) |
| 2025 | 1,048 million | 0.172% | Sum of EPA AER public-supply water, 16 licensed data-centre installations |
| 2024 | 752 million | — | Sum of EPA AER public-supply water, 48 data centres (The Journal's analysis) |
| 2025 | 999 million | — | Sum of EPA AER public-supply water, 48 data centres (The Journal's analysis) |
| Annualised | 1,745 million | 0.29% | Uisce Éireann: 57 data centres on the public network, 4.78 ML/day x 365 (averaging period not stated) |
A Dáil written answer in July 2026, citing Uisce Éireann, put data centres at "less than 0.3%" of public supply. Use roughly doubles in hot weather: 1-3 ML/day in Jan-Apr 2026 against 4-6 ML/day in May-Jul 2026, about 0.6–0.9% of the Dublin area's supply at the peak.
Where does the "999 million litres" figure come from?
The Journal Investigates reported 999 million litres for 2025 in July 2026. That was a valuable piece of work, and it is often repeated as if it were a meter reading.
It is not. Adding up the public-supply water rows of the EPA annual environmental reports reproduces it: 752,109 cubic metres for 2024 exactly, and 999,196 cubic metres for 2025 once K2 Strategic's report is left out. With K2 included our total is 1,048 million litres.
So the number is self-reported by licensed sites, which are the big ones. Uisce Éireann's own figure for its 57 connected data-centre sites, 4.78 million litres a day, would come to about 1.7 billion litres over a year.
Which data centres use the most water?
| Site | EPA licence | Litres, 2025 | Litres per MWh of grid power |
|---|---|---|---|
| Runways Information Services Limited (Meta) | P1192 | 557 million | 471 |
| Equinix Hyperscale 1 (DB5) Limited | P1168 | 398 million | 2,453 |
| The other 14 reporting sites | — | 93 million | median 12.9 |
Two sites use 91% of the measured total. Per unit of electricity, Meta's Clonee campus uses about 471 litres per MWh and Equinix's Blanchardstown site about 2,453. The median for everyone else is 12.9.
Our reading. This is a cooling-design story, not a sector story. Most Irish sites use outside air and barely touch the mains. Two use evaporative cooling heavily. Meta's and Equinix's reasons are not public; it is a fair question to ask them.
Two sites use most of the data-centre water
One Meta site and one Equinix site used 91.1% of licensed data centres' public water in 2025; most other sites use a few litres per MWh.
Panel A splits the 1,048 million litres of public-supply water that EPA-licensed data centres reported for 2025 by site. Panel B divides each site's water by the electricity it drew, on a log scale, so each step is ten times the last: the median for the other 14 sites is 12.9 litres per MWh, while Equinix's site used 2,453. The reports do not say what the water is used for; a spread this wide is consistent with different cooling designs (our reading, not stated in the reports). The dashed line is the 6,000 litres per MWh a research paper assigns to generating Irish electricity, which happens at power stations, not data centres.
Sources: EPA annual environmental reports, Table 5 'Water used', 3 Oct 2026 · Fearon, Bresnihan & Brodie, 'How we all pay for Big Tech', MUSSI Working Paper 31, Maynooth University, Sept 2026
Is it a lot?
About 1.05 billion litres is roughly 419 Olympic pools a year, or the daily water of about 21,581 people at 133 litres a day. Nationally, that is small. Six pharmaceutical plants used over 4 billion litres across 2024–25, and Aughinish Alumina over 10 billion (The Journal, from EPA reports).
Locally and seasonally, it is less small. Both heavy users are in the greater Dublin area, where water demand hit a record in May 2026, and data-centre use peaks in hot weather, when supply is tightest.
Data-centre water use, on one scale
Licensed data centres drew about 2.9 million litres a day of public water in 2025, about 0.17% of the 1,700 million Uisce Éireann treats daily; the much bigger "46 billion litres" figure is water used to generate their electricity, not water they draw.
Each square's area is proportional to litres per day, so the red square (data centres' metered public-supply water, 1.05 billion litres in 2025 from 16 EPA-licensed sites) can be compared directly with Dublin's and the country's supply. Uisce Éireann's own figure for the 57 data centres on its network, and reported summer peaks, are higher but on the same small scale. The dashed square is a modelled footprint: data centres' electricity multiplied by 6 litres per kWh used at power stations, which is a different quantity from water piped to the sites. National totals hide local pressure: most sites are in the Greater Dublin Area.
EstimateDaily figures are annual totals ÷ 365; household equivalents use the CSO 2022 median household use. The 57-site and summer figures were released to a TD and reported by The Journal; no primary document is public.
Sources: EPA annual environmental reports (Table 5, water used), 3 Oct 2026 · Uisce Éireann press release on 2024 annual report, 30 Jun 2025 · Irish Times (citing Uisce Éireann), 29 May 2026; UE press release 10 Jul 2026 (693 ML record), 29 May 2026 · The Journal, 24 Aug 2026, 24 Aug 2026 · Fearon, Bresnihan & Brodie, 'How we all pay for Big Tech', MUSSI Working Paper 31, Maynooth University, Sept 2026 · CSO, Domestic Metered Public Water Consumption 2022 - Key Findings, 20 Nov 2023
What is the "46 billion litres"?
A Maynooth working paper estimated a 46 billion litre "water footprint". That counts water used to generate the electricity, at 6 litres per kWh, and applies it to 9.4 TWh, an EirGrid forecast, rather than the CSO's metered 7.7 TWh. It measures something different. Never add it to direct use.