Does Irish Water even know how much water data centres are using?

According to Irish Water, as of 2021, data centres across Ireland drank about 810 megalitres of water from the public mains a year – which is about 0.13 percent of overall national supply. 

But that same year, Meta reported that it withdrew 928 megalitres of water for its data centres in Clonee in Meath. Planning documents say that it was to rely on water from the mains. 

That’s more than Irish Water said was consumed overall in the country that year. 

A spokesperson for Irish Water said on 19 June that it couldn’t lay out its methodology behind the 810 megalitres figure – or give more up-to-date figures on water use by data centres, since the AI boom. 

Data centres are just one type of non-domestic customer, said the spokesperson. 

“We don’t analyse them uniquely in planning for future demand as they would represent a very small percentage of current and future non-domestic use,” they said – “less than 1% of overall demand”.

Much of the debate around data centres has focused on the climbing percentage of the country’s electricity that goes to data centres – which had hit 22 percent, as of 2024.

But the gap in figures for water consumed by data centres in Ireland has also started to draw more attention – and breed mistrust.

Environmental activists and politicians are missing key info as they try to navigate narratives around water use, and cooling technologies, and knock-on impacts, and how policy is taking this into account.

When Jessika Roswall, the European Commissioner for the Environment, came to speak to the Oireachtas Joint Committee on Climate, Environment and Energy on 11 June, she circled back to water use a few times.

“This is a question that we also need to address, because data centres, AI and so on are really important for Europe for being competitive and secure, but we also have to be very mindful of how we distribute or use water in a smart and efficient way,” she said.

Yet, there isn’t much detail available about water use of data centres in Ireland, said Labour Party TD Ciarán Aherne, who sits on that committee.

He asked the Minister for the Environment on 19 June for figures on water use by data centres. But got back roughly the same overall figure for Irish Water that has been floating around for years.

That it’s estimated at below 0.2 percent of total annual consumption. “I understand Uisce Éireann is currently carrying out a review of data centre businesses with a view to having updated analysis this year,” said the minister’s response.

Elaine McGoff, head of advocacy with An Taisce, said it’s been frustrating trying to get a handle on how much water is used by data centres – and which water catchment they are in. 

Because talking about national supply isn’t that useful, given they’re concentrated in particular areas, she said. “How do data centres impact on this specific area?”

Where’s it coming from?

Back in 2021, industry analysts at Host counted 70 operational data centres in Ireland, and another 8 under construction.

Irish Water told a councillor in South Dublin County Council at the time that its 810 megalitres figure was based on 24 data centres being connected to the mains supply.

And the others? For data centres that are cooled by water, that water may be drawn from different sources, says a spokesperson for Irish Water. 

“In respect of those Data Centres that are cooled by water, that water may be sourced from boreholes or from the public water supply (or a mix of both),” they said.

Irish Water knows how much water it supplies daily and monthly across the country, they said. But “we cannot outline how much water is utilised cooling a Data Centre should a Data Centre have alternative sources of water.” 

As the public water supply in some areas becomes more stressed, data centre operators are exploring greater use of groundwater, to prevent competition between water for homes and water for data centres.  

But so far, there’s no public data showing how much it is already happening. 

The Environmental Protection Agency registers and tracks who is drawing water from groundwater with private boreholes. 

Anybody sucking up more than 25,000 litres a day has to register with the EPA, and possibly apply for a licence. 

But there aren’t any data centres on that list. “The register has been reviewed, and it can be confirmed that currently there are no data centres registered for groundwater abstraction or otherwise,” said an EPA spokesperson. 

A spokesperson for Irish Water said it couldn’t say how many data centres it counts as connected exclusively to the public water supply, how many are a mix, and how many rely solely on boreholes. 

“Uisce Éireann has no information in relation to the use of private water sources such as boreholes as that is outside the utility’s remit,” they said.

McGoff, head of advocacy with An Taisce, said that she sees challenges with drawing from either the mains, or directly from groundwater, or rivers and lakes. “Each have problems,” she said. 

The Greater Dublin Area water supply is severely stressed. Uisce Eireann is struggling to meet the needs of residents from the Poulaphouca Reservoir, she said. 

Hence the Shannon pipeline project, Uisce Eireann’s plan to bring water from the Parteen Basin on the River Shannon to Peamount to supply the thirsty Dublin region.

But encouraging data centres to pull from groundwater or water bodies, instead of through the mains, would have risks, said McGoff. 

Some data centres say that they switch to water cooling, from air cooling systems, when the temperature hits 25 degrees celsius, she said. 

But just as that’s when households need the water, it’s also exactly when these water bodies start to run low, she said. 

And when water levels drop in water bodies, it concentrates the pollution in the water, she said. “That’s when the ecological problems get amplified,”

Said McGoff: “The pollution effect will be greater, the water will be warmer, the fish will die.”

Whether it makes sense to draw from groundwater or mains depends on where you are, said Kaveh Madani, director of the United Nations University Institute for Water, Environment and Health. 

It’s the same as when people ask him about the suitability of hydropower, he says. “Immediately, I say, where?”

Because the local conditions of the site are key, he said. “How much water do you have? Is it fossil groundwater or renewable groundwater?”

And, what is the impact of any discharged water, he said. “If you are putting heating water back into a stream, it can increase the water temperature and damage the ecosystem.” 

Cooling considerations

Irish Water’s data was based on 24 data centres connected to the mains, at a time when there were an estimated 70 operational data centres in Ireland. But that’s now far in the rear-view mirror.

By 2023, there were an estimated 123 data centres in Ireland, says a European Commission report published in July last year.

Under the EU’s Energy Efficiency Directive, data centres with power demand of 500kw and over have been required to report each year their annual water, and energy uses, to the European Commission.

But operators for just 15 percent of these data centres in Ireland – 18 of them – submitted data to the commission, outlining water and energy use, in the first round of data collection.

Together, those 18 used 627 megalitres of water that year, they said. Water input is defined as water that enters the data centre boundary for operational purposes.

A spokesperson for the Department of Climate, Energy and Environment said they couldn’t give an updated figure for how many data centres have now reported. 

“The Department is not in a position to provide a specific answer to this question, as the reporting process for all reporting cycles is ongoing and therefore not yet finalised,” they said.

The regulation doesn’t include any penalties for data centres that don’t report, said the spokesperson. “However, it is intended that this will be addressed as part of compliance measures being legislated for in Ireland’s transposition of Article 12(1) of the [Energy Efficiency Directive].”  

Still, “it’s a shockingly low figure,” said Aherne, the Labour TD and spokesperson on climate, environment and energy, of the number that submitted figures ahead of that report.

He doesn’t understand why the government isn’t publicly naming and shaming those that aren’t transparent about usage, he said. 

The European Commission report said, of the low submissions, that “Ireland struggled to implement the necessary systems for effective data collection”.

Also, it said, data centres in “colocation” centres – where the operator is basically a landlord for rack space, and customers manage their own services and equipment –  may not have access to the full set of indicators and data about performance, may collect data in different ways, or have had trouble navigating the reporting system. 

Cooling down

Several data centres operators  – including Equinix, ColoCrossing, and EdgeConnex –  didn’t respond to queries for up-to-date figures on water use for cooling in their data centres in Ireland.

But responses, and planning documents, do suggest vast variations in water use for cooling, depending on the technologies in the buildings.

A spokesperson for Digital Realty – which runs eight data centres in Ireland – said it had carried out its reporting under the directive. But they wouldn’t share figures directly.

But a spokesperson for Servecentric, a data centre services provider, said that it is based in a facility owned and operated by Digital Realty in Blanchardstown.

They use a portion of the cooling for the facility they are in, they said, and the system in place means that it’s a small amount.

“We utilise a closed-loop chilled water system, so our annual water consumption is negligible,” they said. “We have no plans to introduce any additional water cooling to the cabinet at this time.”

Meanwhile, an AWS spokesperson said that its operations in Ireland withdrew about 109 megalitres of water in 2025. 

That gives its centres a “water usage effectiveness” rating – the metric used to convey how much water is used per unit of computing power – that’s more than 40 times the global industry average, they said.

A spokesperson for Microsoft didn’t give exact figures, but said it plans to share more detail over the coming weeks about water use at its data centre campus in Grange Castle. “Its water use is very low”, they said.

“Our water use is low because cooling (and therefore water use) is only required at Grange Castle when the outside air temperature exceeds 29.4°C,” they said. 

That’s rare in Ireland, and so, for the vast majority of the year our cooling uses no water at all, they said.

The Microsoft spokesperson said that cooling technologies are chosen carefully to take into account where centres are. “This approach is chosen specifically because it makes the most of Ireland's climate to keep both energy and water intensity low.  

They’re also shifting to zero-water cooling in new projects, they said – to closed-loop liquid cooling technology.

A spokesperson for Pure DC – with data centres in Ballycoolin – said it uses closed-loop water cooling at its campus there. “So there is zero operational water use,” they said.

“Water use on site is for services such as staff kitchens, toilets, and showers and consistent with light commercial use from other sectors,” they said.

“While we understand the public's concern about water use by data centres, most of the issues are in the US from older generation data centres, rather than the campuses across the UK & Ireland which are increasingly efficient,” they said.

There are complexes in Ireland like Meta in Clonee, though, that use more than zero water – and they aren’t all old.

A wide grey road runs through the IDA Business and Technology Park in Blanchardstown. On Monday late morning, the grass verges were uniform and trimmed, and the trees were evenly spaced. 

At its western end sit Equinix’s big data centres, with massive silver water towers, tall fat tubes behind a high fence.

The data centre operator finished its first big data centre building here in November 2022, and a second was up a year later. A third is on the way.

Once the trio are all up and running, they’ll probably consume about 300 megalitres of water a year, said Equinix, in planning documents back in April 2020.

Using water-heavy cooling technology, though, means less electrical energy consumed by the site, saving 41,000 MWHr per year, the document says, “which is significant”.

McGoff, of An Taisce, says she is conscious of the wider context that a data centre using little water may, on the flipside, be using more electricity. That it can be a trade-off, she said.

The need to look beyond a single scrap of data about a data centre’s resource use – and consider different points altogether – is raised in a report by the European Commission published last October.

Single indicators can mislead. A data centre may have high energy efficiency which looks great, but it may also rely on fossil fuels, it says, or it may rely on fossil fuels but reuse waste heat. 

And, “since the use of water-intensive evaporative cooling is a very effective measure for reducing energy consumption, there is a well-known conflict of objectives between water consumption and energy consumption,” it says.

In other words, using more water can mean using less energy.

All these complexities are why McGoff gets so frustrated with the lack of transparency about data centres, she said.  

The lack of verified and public data around how many data centres there are exactly, what technologies they rely on, how much water and energy they actually use.

 “If you’re not using very much, prove it,” she said. 

Indeed, the shortcomings of the conversation about water use, and how it is tracked, go further still, says Madani, the water scientist at United Nations University Institute for Water, Environment and Health. 

Public debate is obsessed with the water used for cooling, he said. But this is just one element of the water footprint of data centres, he said. 

How much water do data centres use? “It depends on which part of the value chain we talk about,” he said. 

There’s the water footprint from manufacturing semiconductors, from the construction, from mining the critical minerals, he said. “In every step, you have a water footprint.”

It’s easy to confuse people with all the terminology, he said.

But people should ask the question about water impacts across the value chain, he said, – it’s just not a comfortable question that people want to ask.

If he tells people that the battery for his electric vehicle depended on mining lithium and worsening drought in parts of Bolivia, it sounds ugly, said Madani. “So, selfishly, we discard all this and take only a piece of the problem.”