Do Data Centers Use a Lot of Water?

By Naperville Guide · Published October 8, 2026

Short version: do data centers use a lot of water? The thirsty ones, yes. A medium-sized data center with evaporative cooling uses around 300,000 gallons a day — roughly what 1,000 households use. The biggest ones can top 5 million gallons a day. But "data center" covers everything from a closet of servers to a gigawatt campus, and the newest designs barely sip. Here's the verified picture, with the Naperville angle.

How much water a data center actually drinks

Servers turn nearly all their electricity into heat, and heat has to go somewhere. The cheapest way to remove it at scale is evaporative cooling: run water through cooling towers, let it evaporate, and the phase change carries the heat away. It works — and it consumes fresh water continuously, because evaporated water doesn't come back.

The range is enormous because cooling designs differ enormously:

The honest caveats: a data center on air cooling or a closed loop uses almost no water on site — it just uses more electricity instead. And there's a real shift underway: the newest AI chips run so hot they need liquid cooling, which circulates coolant in sealed loops with near-zero fresh-water consumption. Any honest answer to "how much water does a data center use" has to start with "which kind."

Where Naperville's water comes from

Here's the local foundation: Naperville's drinking water is Lake Michigan water, purchased through the DuPage Water Commission from the City of Chicago — that's straight from the city's own water quality report. The city runs its own municipal water utility, so your rates are set locally.

Two things worth knowing about that supply. First, the lake itself is legally guarded: the 2008 Great Lakes Compact, signed by eight states and two Canadian provinces, generally bans piping Great Lakes water outside the basin. The constraint for Naperville isn't the lake running dry — it's local pipes, treatment capacity, and what the city pays Chicago and the Commission for wholesale water.

Second, regional water pressure is real and Naperville sits at the center of it. The DuPage Water Commission is currently building WaterLink, a 30-mile, 54-inch water main that starts in Naperville and runs west to Montgomery, Oswego, and Yorkville — about six miles of it inside Naperville city limits, with construction on Book Road running through spring 2027. Why? Those towns' current source, the Ironton-Galesville deep sandstone aquifer, is projected to be unable to meet demand as early as 2050. When aquifers run short, everybody looks to the lake.

The water fights already happening in Illinois

This isn't theoretical. Two Illinois fights are live right now:

• The Mahomet aquifer. Near Champaign-Urbana, a proposed data center drew protests after months of secret talks surfaced through public-records requests. The aquifer in question provides drinking water to nearly a million people across 14 counties. The draft agreement would cap the project's potable-water initial fill for closed-loop cooling at 750,000 gallons per phase — a number that tells you how seriously negotiators take the aquifer.
• Joliet. Residents sued in May 2026 to stop a $20 billion, 795-acre, 24-building data center campus in Will County, arguing it could draw 100,000 to 150,000 gallons a day from an aquifer already projected to fall short of peak demand by 2030 — before Joliet's planned switch to Lake Michigan water.

The pattern: where data centers tap aquifers, neighbors push back hard. Where they tap Lake Michigan systems, the question shifts to infrastructure and cost. No data center in Naperville itself has been publicly announced — worth saying plainly, because the anxiety often runs ahead of the facts.

Who pays when a giant new user hooks up

This is the "will it raise my bill" mechanism, and the guardrail is real: water utilities generally charge big new developments one-time connection or capacity charges — tap fees, system development charges — scaled to the infrastructure the new user requires. The industry principle is explicit: system expansions should be funded by the newcomers, not absorbed by existing customers' rates.

Now the honest Naperville wrinkle: your water bill is already climbing for infrastructure reasons that have nothing to do with data centers. Starting January 2026, the average residential combined water/wastewater bill is $118 a month. The city's own rate study found Naperville is more than 50 miles behind on water main replacements. The Springbrook treatment plant upgrades are the largest capital project in city history, running through 2030. Rate adjustments are averaging 23% a year for water and 10% for wastewater over three years. So if a giant new user ever did connect here, it would add demand pressure on top of a bill trajectory already heading up because of aging pipes.

What this means for your water bill

• No direct threat today. No data center in Naperville has been announced, and connection-fee structures are designed to make big users pay for the capacity they require.
• Watch the capital charges. The "water capital charge" line on your Naperville bill is where infrastructure spending shows up. That's the line to compare year over year.
• Wholesale costs flow through. What the city pays the DuPage Water Commission and Chicago eventually lands in rates — big regional demand growth is a slow upward pressure, not a sudden spike.
• The electric side matters more right now. Data centers are already moving wholesale power prices — we covered exactly how yesterday. Water is the second front, not the first.

Good to know