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Comment by whall6 | Hacker News Reader

New Gen data centers are closed loop and don’t use water at nearly the same rate as previous generations

There's also a power generation water cost though!

Something like 500g/MWh for gas/coal/nuclear (~70% of power in AZ), so a huge xAI datacenter (Colossus 2, ~1 GW/h) would use ~700 MW of this type, or ~350k gallons of water an hour, which would be 0.2% of the Colorado rivers flow rate last year.

I don't know if that's significant.

Pulling recent data from the EIA, of the roughly 10,000 megawatts of new power capacity installed in Arizona between 2023 and 2025, 50% is batteries, 40% solar, 6.5% wind, and 3.5% gas. Now, most solar and wind plants rarely if ever hit their nameplate capacity, but it’s pretty clear the large majority of new power generation isn’t consuming water. https://www.eia.gov/electricity/data/eia860/

Does that change the math above if they're tied into the grid?

If they're tied directly to the renewables (Meta is doing this in some places), then true, not a technical increase. But you could still maybe claim they're instead preventing the equivalent reduction on average/grid (and, say, decommission of some of that coal). I suppose that's a separate point.

If it’s truly separated (no interconnect agreement) or generation capacity is below 1 MW, it won’t show up in EIA data, yes. Rooftop solar is also not included in the data for that reason.

It's the type of situation where that amount of water use isn't going to move the needle very much even in the desert, but building thermal power plants there there is still kind of silly because a) deserts are generally well-suited to solar, and b) you could also build thermal power plants in places like the midwest where that amount of water use is totally irrelevant.

Got an example? I'm pretty sure new datacenters are still using cooling towers.

QTS is building a second campus in Chicago with closed loop

https://q.com/resources/how-qts-data-centers-use-closed-loop...

Ok, those are truly closed loop. As in, they use ambient cooling or active chillers. I've seen too many cooling tower sites described as closed-loop because the internal system is.

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