Turn a data center's megawatts into gallons of water a day, on site and at the power plants that feed it, using the federal government's 2024 data center report.
Water rates: Lawrence Berkeley National Laboratory, 2024 United States Data Center Energy Usage Report (LBNL-2001637): average on-site water use of "just over 0.36 L/kWh through 2023", rising to "between 0.45 and 0.48 L/kWh" (p. 48), and 4.52 L/kWh of water used to generate the electricity data centers draw (p. 57). Household figure: EPA WaterSense, "The average American family uses more than 300 gallons of water per day at home." Facility capacities come from our data center map records and are estimates.
A 100 MW data center running at full capacity uses about 228,245 gallons of water a day on site, at the 2023 U.S. average rate. That is the same as the daily home use of about 761 families, and generating the electricity it draws uses about 2,865,738 more gallons a day at the power plants.
The calculator produces these figures from a facility's size, so you can run your own number. It uses national averages and does not measure any one facility. It runs in your browser, and nothing is sent anywhere.
The calculator has four inputs. Fill them in this order:
The results appear in three boxes. On-site water shows gallons a day used at the facility. Same as shows how many families' home use that equals. At the power plants shows gallons a day used to generate the electricity. A result sentence also gives the on-site figure for a year.
Three buttons sit under the result. Copy result copies the sentence, the math, the sources and a link. Copy share link copies a link that reopens the same inputs. Print prints a one-page sheet with the result, the math and the sources. A link from a facility on the data center map can open this calculator with the megawatts already filled in.
The calculator reports two water measures, and they are different. Site water use effectiveness counts only water used at the facility, mainly for cooling. Source water use effectiveness adds the water used to generate the electricity the facility draws. The Lawrence Berkeley National Laboratory (LBNL) says that including both "reflects the true water cost of data centers."
The power plant figure is far larger. LBNL puts the on-site average at just over 0.36 liters per kWh through 2023. Its indirect figure for data center electricity is 4.52 liters per kWh, so each kilowatt-hour draws about 12.6 times as much water at the power plant as on site. The overall U.S. electricity average is 4.35 liters per kWh.
The national totals are large too. U.S. data centers used about 66 billion liters on site in 2023, up from 21.2 billion liters in 2014. Their indirect water footprint was nearly 800 billion liters. Hyperscale and colocation data centers accounted for 84% of the 2023 on-site total. Data centers used about 176 terawatt-hours of electricity, or 4.4% of U.S. electricity use.
The calculator runs this arithmetic. You can repeat it by hand with the same inputs.
These are the worked examples the calculator produces with the 2023 rate unless noted:
Every on-site and power plant figure scales in a straight line with megawatts and share in use. The 1,000 MW example is ten times the 100 MW example, so each of its figures is ten times as large.
The result is an average-based estimate, and it is not a measurement of any facility. Data centers do not publish their real average power draw facility by facility. Stated capacity is a maximum, so 100% is an upper bound, and a facility may use less.
The calculator does not ask about a facility's cooling system; it offers only two cooling water rates. LBNL says data centers can reduce on-site water use with airside economizers, which cool with outside air and let them shut down chilled-water systems in favorable weather. Some hyperscale facilities report on-site rates of 0.1 to 0.3 liters per kWh for such systems. The calculator offers only 0.36 and 0.48, so this figure is worked by hand: 2,400,000 kWh × 0.3 = 720,000 liters, and 720,000 ÷ 3.785411784 is about 190,204 gallons a day on site for 100 MW at 100%.
Low on-site water is not always better. LBNL names a tradeoff between low energy use and low on-site water use, and water-cooled chillers can save energy but use water. When you read a facility's numbers, ask about energy and on-site water together.
The method also does not count power purchase agreements or on-site "behind the meter" generation. Either could change a facility's real figure. The application, the permit or the water utility may give the real figure. The calculator cannot.
Describe the figure as what it is: an estimate built from the 2023 national average, with 100% of stated capacity as the upper bound. Name the source as LBNL's 2024 United States Data Center Energy Usage Report, report LBNL-2001637, published December 2024.
Then ask the applicant for the real figures in writing:
Put these questions in a letter you can bring to the hearing. The data center public comment letter builder writes a letter you can send or read aloud at the hearing; paste your questions into its "In your own words (optional)" box. Use the data center map to find the capacity of a tracked facility near you, and enter it in the calculator to get the figures for your comments.
For a comparison with farms, read the explainer on data centers and agriculture water use. For a wider look at AI's water use, read the explainer on AI water use. Start by filling in the four inputs above, then copy the result and the math into your notes.
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