The Cost Nobody Models
When a hyperscaler evaluates a new data center site, the financial model typically has fifty line items for power — energy charges, demand charges, transmission riders, capacity payments, fuel adjustment clauses, renewable energy credits — and zero line items for water.
This is a problem. A 100 MW evaporative-cooled facility in Phoenix consumes roughly 530,000 gallons of water per day. At Phoenix's summer commercial rate of $8.19 per thousand gallons, plus sewer charges, that single facility's water bill can exceed $3.3 million per year — equivalent to $3.77 per MWh of IT load. That is not a rounding error. On a 20-year lease, it is a $66 million operating cost that most procurement teams discover after the site is selected.
WUE measures liters of water consumed per kilowatt-hour of IT energy. Developed by The Green Grid in 2011, it is the water counterpart to PUE (Power Usage Effectiveness). Lower is better. Evaporative-cooled facilities typically range from 1.0 to 2.5 L/kWh depending on climate. Air-cooled and liquid-cooled facilities approach zero.
The industry average WUE across all data centers is approximately 1.9 L/kWh. Hyperscalers have driven this down — AWS reports 0.19 L/kWh globally, Meta targets 0.20 L/kWh for new builds — but the fleet average masks enormous variation by site. Microsoft's Arizona facilities run at 1.52 L/kWh, roughly 8x the company's Singapore deployments (0.02 L/kWh), because Arizona relies on evaporative cooling while Singapore uses closed-loop air-cooled chillers.
The point is not that water costs dominate a data center's operating budget. Power will always be the largest line item. The point is that water costs vary by 5-10x across markets, and that variation is large enough to shift site selection rankings when modeled correctly.
How Water Tariffs Work
Electric utility tariffs are familiar to most energy procurement teams. Water tariffs are structurally simpler but unfamiliar — and the differences matter.
Volumetric Charges: Tiers, Not TOU
Power tariffs price energy by time-of-use: on-peak, off-peak, super off-peak. Water tariffs price volume by consumption block: the more you use, the higher the marginal rate.
A typical large commercial water tariff has 2-4 tiers. For example, Loudoun Water — the utility serving the highest-density data center cluster in the world — charges:
- Tier 1: $4.42/kgal (first block)
- Tier 2: $7.59/kgal (all usage above threshold)
Some utilities use incremental tiers where only the marginal gallons above the threshold are charged at the higher rate. Others use cumulative (ratchet-style) tiers where crossing the threshold reprices all usage at the higher rate. The billing mechanism matters: a 100 MW data center will always be in the top tier, so incremental vs. cumulative changes the effective blended rate.
Water utilities bill in one of two units. CCF (hundred cubic feet, equal to 748 gallons) is common in western states. kgal (thousand gallons) is common in eastern states. Portland bills at $8.17/CCF, which converts to approximately $10.92/kgal. Always check units when comparing rates across utilities.
Fixed Service Charges: Meter Size Is the Multiplier
Unlike power, where fixed charges are modest, water fixed charges scale dramatically with meter size. Data centers require 4" to 12" meters to support cooling tower makeup flow rates.
| Meter Size | Loudoun Water (quarterly) | DC Water (monthly) | Denver Water (monthly) | |---|---|---|---| | 2" | $551.62 | $15.14 | $92.28 | | 4" | $2,229.43 | $275.81 | $347.67 | | 6" | $3,125.80 | $538.37 | $774.79 |
Fairfax Water — serving the county adjacent to Loudoun — charges only $52.73/month for a 4" meter, roughly one-fifth of DC Water's equivalent. These fixed charges are often overlooked but compound to six-figure annual differences on large installations.
Seasonal Pricing: Summer Peaks Compound
Most water utilities impose seasonal rate adjustments. Phoenix Water charges three seasonal tiers:
- Low season (Dec–Mar): ~$6.59/unit
- Mid season (Apr–May, Oct–Nov): ~$7.39/unit
- High season (Jun–Sep): ~$8.19/unit
This matters because evaporative cooling consumption is not linear across the year. WUE spikes in summer when ambient wet-bulb temperatures rise — precisely when seasonal rates are at their peak. A 100 MW facility in Phoenix might consume 17,000 kgal in January but 41,000 kgal in July. Multiplying peak consumption by peak pricing creates a compound effect that annual-average models systematically understate.
Our analysis shows that using an annual-average WUE and blended rate for Phoenix underestimates annual water costs by approximately 15% — roughly $500,000 per year on a 100 MW facility.
The Sewer Problem
The largest water cost for many data centers is not the water itself. It is the sewer.
Most municipal wastewater authorities charge a per-gallon sewer rate applied to metered water consumption. Unlike power, where transmission and distribution are embedded in the rate, sewer is often billed by a separate entity at a separate rate — sometimes exceeding the water rate itself.
DC Water illustrates the magnitude. In FY2025, DC Water's potable water rate is $9.40/kgal. Its sewer rate is $16.41/kgal — 75% more than the water rate. For a facility connected to DC's municipal sewer, the sewer charge is the dominant cost component.
This creates two optimization levers that procurement teams should model explicitly.
Sewer Deductions
Evaporative cooling towers consume water — it evaporates. The evaporated volume never enters the sewer system. Most utilities allow a sewer deduction for demonstrated consumption, typically proven via sub-metering the cooling tower makeup water line or engineering calculations based on cycles of concentration.
A 50% sewer deduction on a facility discharging 200,000 kgal/year at DC Water's $16.41/kgal rate saves $1.64 million annually. This is one of the highest-impact operational optimizations available — and it requires nothing more than installing a sub-meter and filing the right paperwork.
Blowdown and High-Strength Surcharges
The water that does enter the sewer after evaporative cooling is not ordinary wastewater. Cooling towers operate by evaporating pure H₂O, leaving behind concentrated minerals. The discharged blowdown water has elevated Total Dissolved Solids (TDS), chlorides, and scale-forming minerals that require additional treatment at the wastewater plant.
Many municipal wastewater authorities charge industrial waste or high-strength surcharges for discharge exceeding residential-grade TDS thresholds. These surcharges can add $1-5/kgal on top of the base sewer rate, partially offsetting the savings from the sewer deduction.
The net economics depend on the specific utility's surcharge structure, the source water quality, and the cooling tower's cycles of concentration. A facility operating at 5 cycles of concentration (typical) on moderately hard source water will produce blowdown at roughly 5x the inlet TDS — often enough to trigger industrial discharge surcharges.
Reclaimed Water: The 50% Discount
Reclaimed (recycled) water is treated municipal wastewater that has been purified to a level suitable for non-potable applications — including cooling tower makeup. It is delivered through a separate "purple pipe" distribution system and is typically priced at 30-80% below potable rates.
Loudoun Water: The National Model
Loudoun Water operates a 20-mile dedicated reclaimed water pipeline explicitly built to serve data centers in the Ashburn corridor. In 2024, this system delivered 736 million gallons of reclaimed water to data center customers.
The economics are compelling:
| Source | Rate ($/kgal) | Annual Cost (100 MW facility) | |---|---|---| | Loudoun Water — Potable (blended) | ~$5.50 | ~$1.47M | | Loudoun Water — Reclaimed | $2.07 | ~$554K | | Savings | 62% | ~$920K/year |
Over a 20-year facility life, switching from 100% potable to 100% reclaimed at Loudoun Water rates saves approximately $18.4 million — without changing any equipment. The cooling tower does not care whether the makeup water was reclaimed or potable, as long as it meets minimum quality standards.
Only a fraction of US water utilities offer reclaimed water programs, and fewer still have the purple-pipe infrastructure to deliver it to data center sites. Loudoun Water, San Antonio SAWS, Las Vegas (SNWA), Fort Worth, and Quincy, WA (where 95% of data center cooling makeup is reclaimed) are among the leaders. Checking reclaimed water availability should be a standard item in any site selection due diligence.
The Quincy, Washington Model
Quincy, Washington — home to Microsoft, Yahoo, Dell, and Sabey data centers — demonstrates an alternative approach. Rather than a utility-operated reclaimed system, the City of Quincy's municipal water reclamation facility (MWRF) provides treated effluent directly to data center operators. An EPA case study documented that 95% of data center cooling makeup water in Quincy comes from reclaimed sources.
The combination of cheap hydroelectric power (Grant County PUD) and near-free reclaimed cooling water makes Quincy one of the lowest total operating cost data center markets in the US — a ranking that only becomes visible when water is modeled alongside power.
The Will-Serve Problem: When Rates Don't Matter
A utility might publish attractive rates on paper, but if it cannot physically deliver the volume a data center requires — or if local politics have imposed a moratorium on new large-volume hookups — the published rate is irrelevant.
This is not hypothetical. Several dynamics are constraining water availability in major data center markets:
Drought and allocation limits. In the Colorado River Basin, municipal water providers are operating under reduced allocations. Phoenix, Las Vegas, and Salt Lake City have all experienced periods where new large commercial connections were delayed pending confirmation of long-term supply adequacy. Southern Nevada data centers consumed 716 million gallons in 2024 — a figure that draws increasing scrutiny from water authorities and local advocacy groups.
Infrastructure capacity. Columbus, Ohio — the 10th largest data center market — is planning a $2 billion new water treatment plant driven in part by data center demand growth. Until that plant is online, new large connections face capacity constraints on the existing system.
Political risk. In Hillsboro, Oregon, public debate has emerged over whether data centers are paying their fair share of water infrastructure costs. The Tualatin Valley Water District charges $94.57/month for a typical residential bill while industrial rates are only marginally higher — a gap of less than 2% that has generated community opposition to further data center development.
A will-serve letter is a utility's written commitment to provide water and/or sewer service to a specific property at a specified capacity. For data centers, securing this letter — not the published rate — is often the binding constraint on project timelines. Some jurisdictions require proof of long-term water supply adequacy before issuing will-serve commitments for large loads.
Any site selection model that includes water costs should also flag capacity constraint status — whether the local utility is open to new large connections, constrained, or under active moratorium. The cheapest rate in a constrained market is worth nothing if the tap cannot be turned on.
System Development Charges: The Upfront Capital Hit
Beyond ongoing volumetric rates, most water utilities impose System Development Charges (SDCs) — one-time capacity fees assessed on new connections to recover the cost of infrastructure built to serve growth.
SDCs scale by meter size, and at data center scale, they can be significant:
- A standard residential 1" meter might carry a $5,000-15,000 SDC
- A commercial 4" meter: $50,000-200,000
- A commercial 8" or 12" meter: $500,000-3,000,000+ depending on jurisdiction
Utilities are increasingly redesigning SDC methodologies specifically for data centers. A 2024 Raftelis analysis documented a shift from equivalent residential unit (ERU) based SDCs — which assume all commercial connections scale linearly from a residential baseline — to per-gallon peak-demand based SDCs that estimate actual infrastructure cost causation. For data centers with massive cooling demands, this redesign can substantially increase the upfront fee.
SDCs are capital expenditures, not operating costs, and should not be blended into a $/MWh metric. But they belong in any honest site comparison because a $2.5M SDC difference between two sites is real money that affects project IRR.
Cooling Technology Is Shifting the Equation
The economics described above apply primarily to evaporative-cooled facilities, which represent the majority of large data centers today. But the cooling landscape is changing rapidly.
The Four Cooling Paradigms
| Technology | Water Intensity | Energy Intensity | Trend | |---|---|---|---| | Evaporative (cooling tower) | High (1.5-2.5 L/kWh) | Low | Still dominant for general-purpose compute | | Air-cooled chillers | Near-zero | High | Used in water-scarce or humid regions | | Direct-to-chip liquid | Low (closed-loop) | Moderate | Required for high-density AI GPU racks | | Immersion cooling | Near-zero | Low-moderate | Emerging for highest-density AI pods |
Microsoft announced in December 2024 that all new AI-optimized data centers will use zero-water cooling via chip-level liquid cooling systems. This is driven by two forces: the thermal density of H100/H200/GB200 GPU racks (which exceed the capacity of traditional air-based cooling) and sustainability commitments to eliminate evaporative water consumption.
Even as WUE improves and liquid cooling adoption grows, total data center water consumption continues to increase because capacity is expanding faster than efficiency gains. Google's global water consumption exceeded 6 billion gallons in 2024. The industry's aggregate water footprint will continue growing through at least 2030, even under aggressive liquid cooling adoption scenarios.
For site selection, the cooling technology choice determines whether water tariff analysis is a primary concern (evaporative) or a secondary one (liquid/air-cooled). But even air-cooled facilities require some water for humidity control and fire suppression — and the choice of cooling technology is often constrained by climate, power availability, and capital budget rather than water cost alone.
What This Means for Procurement
1. Model Water Monthly, Not Annually
Evaporative cooling consumption follows a seasonal curve that compounds with seasonal pricing. Using an annual average WUE and a blended rate will underestimate costs by 10-20% in hot climates. Model consumption and rates on a 12-month basis, applying the correct seasonal tier to each month's forecasted volume.
2. Always Check Sewer Separately
In many markets, sewer/wastewater is billed by a different entity than water — and it is often the larger charge. DC Water's sewer rate is 75% higher than its water rate. Denver's wastewater is billed by a completely separate department. Model water and sewer as distinct cost streams with their own rates and providers.
3. Pursue Sewer Deductions Aggressively
A sewer deduction for demonstrated evaporative consumption is one of the highest-ROI operational optimizations available. The upfront cost is a sub-meter and a utility application. The annual savings can exceed $1 million for a large facility. Factor the deduction into your cost model but confirm eligibility with the specific utility — not all providers offer it, and documentation requirements vary.
4. Evaluate Reclaimed Water Early
Reclaimed water availability should be checked during initial site screening, not after the lease is signed. The infrastructure requirement — a separate purple-pipe connection — means reclaimed water is only practical if the utility has existing distribution in the vicinity of the site. Retrofitting a potable-only site for reclaimed water after construction is prohibitively expensive.
5. Confirm Will-Serve Before Modeling Cost
A rate schedule is a menu, not a guarantee. Before investing time in detailed water cost modeling for a site, confirm that the utility can actually serve the requested volume by obtaining (or confirming the feasibility of) a will-serve letter. In water-stressed markets, this is the binding constraint.
6. Include SDCs in Capital Planning
System development charges for large meters can reach seven figures. They do not appear in operating cost models but they are real cash outlays that affect project economics. Include them in your capital budget alongside interconnection costs, transformer procurement, and site preparation.
The Bottom Line
Water is not going to overtake power as the dominant data center operating cost. But at $1.50 to $8.00 per MWh of IT load — depending on climate, cooling technology, tariff structure, and reclaimed water availability — it is large enough to matter in site selection, large enough to optimize, and large enough that ignoring it leaves real money on the table.
The utilities that have invested in reclaimed water infrastructure (Loudoun Water, San Antonio SAWS, Quincy WA) are creating a measurable competitive advantage for their service territories. The utilities that are imposing capacity constraints and moratoriums are creating measurable risk. Both dynamics belong in the financial model.
The data center industry has spent two decades optimizing PUE from 2.0 to 1.1. The next frontier is WUE — and the tariff structures that price it.
See the data behind this research
Every chart in this brief was generated from our production cost model. Explore the same data — or run your own scenarios.