Resources · Glossary
Data center terms, in plain language
Data center applications and hearings use a lot of industry shorthand. These are short, neutral definitions of the terms that come up most. Where a term has a legal meaning in Iowa, we cite the code.
- Backup generator
- An engine-driven generator kept on site to supply power if the utility fails. Federal rules limit how many hours emergency engines may run for testing and maintenance. See water, power and backup generators.
- Colocation data center
- A data center whose operator leases space, power and cooling to other companies. The 2024 LBNL report splits these into smaller retail providers and larger wholesale providers.
- Cooling tower
- Equipment that removes heat by evaporating water. Evaporative cooling uses more water on site than air cooling or direct-to-chip liquid cooling.
- Development agreement
- A contract between a local government and a developer for one project, recording what each side commits to. See what a development agreement is.
- Direct-to-chip cooling
- Liquid cooling that carries heat away from processors through cold plates attached to the chips. It's common with dense AI equipment.
- Enterprise data center
- A data center a company runs for its own use rather than leasing to others.
- Hyperscale data center
- A very large data center built by a company that delivers internet services and platforms at massive scale.
- Immersion cooling
- Cooling in which equipment is submerged in a non-conductive fluid.
- IT load
- The electricity used by the computing equipment itself: servers, storage and networking. It excludes cooling and other building systems.
- Megawatt (MW)
- A measure of power demand at a point in time, equal to 1,000 kilowatts. Data center capacity is often described in megawatts.
- Megawatt-hour (MWh)
- A measure of energy used over time. A 1 MW load running for one hour uses 1 MWh.
- Minimum assessment agreement
- An agreement in an Iowa urban renewal area that sets a minimum taxable value for a property (Iowa Code § 403.6(19)). See development agreements.
- N+1
- A redundancy design with one more unit than the load requires, such as one extra generator or cooling unit, so a single failure doesn't interrupt service.
- Nonregulated water use
- Under Iowa Code § 455B.261, a beneficial use of less than 25,000 gallons of water per day. Larger withdrawals generally need a DNR permit.
- PUE (power usage effectiveness)
- Total facility electricity divided by IT equipment electricity. The closer to 1.0, the less power goes to cooling and other overhead.
- Substation
- Utility equipment that changes voltage between transmission lines and local distribution or a large customer's site. Large data centers often need a new or expanded one.
- Tax increment financing (TIF)
- An Iowa tool under § 403.19 that sends property taxes on new value in an urban renewal area to a city fund that pays for the project's financing.
- UPS (uninterruptible power supply)
- Batteries and power electronics that keep equipment running for the short time between a utility outage and generators starting.
- WUE (water usage effectiveness)
- Water consumed divided by IT equipment electricity, in liters per kilowatt-hour. Site WUE counts water used at the facility; source WUE also counts water used to generate its electricity.
About these definitions. Terms like hyperscale, colocation and N+1 are used informally across the industry and can vary from one company to the next. When a term matters to a decision, ask the applicant to define it in writing.
Sources
- Shehabi, A., et al., 2024 United States Data Center Energy Usage Report, Lawrence Berkeley National Laboratory, December 2024 (data center types, PUE, WUE, cooling): https://eta-publications.lbl.gov/sites/default/files/2024-12/lbnl-2024-united-states-data-center-energy-usage-report_1.pdf
- Environmental Law Institute, Data Centers and Water fact sheet, January 2026 (cooling types): https://www.eli.org/sites/default/files/files-pdf/Data%20Centers%20and%20Water%20Fact%20Sheet%20ELI%20January%202026%20(1).pdf
- 40 CFR 60.4211 (emergency engine operating hours): https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-60/subpart-IIII/section-60.4211
- Iowa Code § 403.6 (assessment agreements): https://www.legis.iowa.gov/docs/code/403.6.pdf
- Iowa Code § 403.19, Division of revenue from taxation — tax increment financing: https://www.legis.iowa.gov/docs/code/403.19.pdf
- Iowa Code § 455B.261 (definitions, including nonregulated use): https://www.legis.iowa.gov/docs/code/455B.261.pdf