90 terms

Data center site selection glossary

The vocabulary of power, land, permitting and deals, defined plainly. Each term links to the guide that covers it in depth.

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2N redundancy: 2N redundancy means a system has two complete, independent sets of components and distribution paths, each able to carry the full load on its own. If one entire path fails or is taken down for maintenance, the other keeps the facility running. 2N costs more than N+1 and is often paired with dual utility feeds or separate substations at the site level. Read the guide →Facilities

A

ALTA/NSPS survey: An ALTA/NSPS survey is a boundary survey prepared to a national standard set jointly by the American Land Title Association and the National Society of Professional Surveyors. It maps boundaries, easements, encroachments, access, improvements and recorded matters from the title commitment, plus optional Table A items the buyer selects. Lenders and title insurers rely on it, and for data center land it often reveals the easements and gaps that shrink buildable area. Read the guide →Deals & diligence
Annexation: Annexation is the legal process by which a city or town extends its boundaries to take in adjacent unincorporated land. For a data center site it can change who controls zoning, who provides water and sewer, which tax rates and incentives apply, and sometimes which electric provider serves the land. Procedures, consent requirements and timelines are set by state law and vary widely. Read the guide →Permitting
ASHRAE TC 9.9: ASHRAE TC 9.9 is the technical committee of ASHRAE that covers mission-critical facilities, data centers and electronic equipment, and it publishes the widely used thermal guidelines for data processing environments. The guidelines define recommended and allowable temperature and humidity ranges by equipment class. Wider allowable ranges let designers use more outside-air or economizer hours, which affects how a site’s climate translates into cooling energy and water use. Read the guide →Facilities

B

Base Flood Elevation (BFE): Base Flood Elevation is the computed water-surface elevation of the flood that has a 1% chance of being equaled or exceeded in any year, as shown on FEMA Flood Insurance Rate Maps for zones such as AE. Local floodplain ordinances often require finished floors or critical equipment to sit at or above the BFE plus added freeboard. The freeboard amount varies by community, so it is checked locally. Read the guide →Environmental
Behind-the-meter (BTM): Behind-the-meter describes generation or storage connected on the customer’s side of the utility meter, so it serves the site’s load directly rather than selling into the grid. For data centers it can mean on-site gas generation, batteries or a co-located power plant feeding the campus. Whether and how a BTM arrangement is allowed depends on state law, the utility and the grid operator’s rules. Read the guide →Power
BESS (battery energy storage system): A battery energy storage system is a set of batteries, inverters, controls and safety systems that stores electricity and releases it on demand. At a data center it can cover short gaps before generators start, shave peaks, support a microgrid or help a site meet a utility’s flexibility expectations. Fire code spacing, setbacks and local permitting for battery installations shape where a BESS can go on the site. Read the guide →Power
Bridge power: Bridge power is temporary on-site generation that serves a data center until permanent utility service is available. It lets a developer energize early phases while transmission upgrades or a new substation are still being built. Common sources are gas reciprocating engines, turbines or mobile units. Bridge power still needs fuel supply, air permits and an exit plan for when the grid connection arrives. Read the guide →Power
By-right use vs. special use permit: A by-right use is one the zoning code permits outright, so approval requires only meeting written standards through site plan and permit review. A special use permit, also called a conditional use, is a discretionary approval granted after a public hearing and review against criteria, often with conditions on noise, setbacks or screening. How a code classifies data centers varies by jurisdiction. Read the guide →Permitting

C

Campus: A data center campus is a single site, or a set of adjoining parcels, planned for several data center buildings that share power, water, fiber and security infrastructure. Campuses are usually built in phases as load ramps up. Planning at campus scale means sizing substations, transmission, roads and utilities for the full build-out even when the first building uses a small fraction of it. Read the guide →Facilities
Capacity market and energy-only market: A capacity market is a wholesale mechanism in which a grid operator pays resources to be available to meet future peak demand, separate from payments for the energy they produce. An energy-only market pays only for energy delivered, relying on scarcity pricing to attract enough supply. Which design a region uses affects how large new loads are planned for and what reliability signals a site selector should watch. Read the guide →Power
Carrier hotel and internet exchange (IX): A carrier hotel is a building where many network carriers, cloud on-ramps and content providers interconnect their networks, and an internet exchange is a shared switching platform where networks exchange traffic directly. Proximity to these hubs, measured in fiber route distance and latency, shapes the value of colocation and edge sites. Remote campuses usually reach them through diverse long-haul or metro fiber. Read the guide →Water, gas & fiber
CHP (combined heat and power): Combined heat and power, also called cogeneration, is on-site generation that captures waste heat from producing electricity and puts it to use, for example to drive absorption chillers. Using the heat raises overall fuel efficiency compared with generating power alone. For data centers, CHP is weighed against simpler on-site options based on gas supply, air permitting, thermal demand and how the system fits redundancy goals. Read the guide →Power
CIAC (contribution in aid of construction): A contribution in aid of construction is a payment a customer makes to a utility to cover the cost of facilities built to serve that customer, such as a substation, line extension or gas lateral. For large data center loads, CIAC can be a major early cost and is often paid before construction begins. How it is calculated, refunded or credited varies by utility and state regulation. Read the guide →Power
Closed-loop cooling and dry coolers: Closed-loop cooling circulates the same water or water-glycol mix through a sealed system instead of evaporating it, so ongoing water consumption is low. A dry cooler is the outdoor heat exchanger that rejects that heat to ambient air with fans, without evaporation. The tradeoff is higher fan or chiller energy on hot days, so climate, power availability and water scarcity drive the choice. Read the guide →Facilities
Colocation: A colocation data center is a facility where an operator provides space, power, cooling and connectivity that multiple tenants lease for their own IT equipment. Retail colocation sells racks and cages, while wholesale colocation leases whole halls or buildings. Colocation sites often favor proximity to metro fiber and carrier hubs, and enterprise and colocation projects commonly fall in the 10–60 MW range on 10–75 acres. Read the guide →Facilities
Contiguous acreage: Contiguous acreage is land that forms one continuous, connected area, without separation by roads, rail, streams, other owners’ parcels or easements that block building. Data center campuses need large contiguous footprints for data halls, substations and setbacks. A tract with plenty of total acres can still fail if a public road, pipeline corridor or wetland splits it into pieces too small or oddly shaped to use. Read the guide →Land
Contract demand and take-or-pay (minimum bill): Contract demand is the amount of electric capacity, in MW, that a customer commits to and a utility agrees to make available under a service agreement. Take-or-pay or minimum bill terms require the customer to pay for a set share of that capacity whether or not it uses it. These terms protect the utility’s investment in new facilities and vary by tariff and negotiation. Read the guide →Power
Critical IT load: Critical IT load is the electrical power drawn by the computing, storage and network equipment a data center exists to run, excluding cooling, lighting and other facility loads. Capacity is often marketed in MW of critical IT load, while the utility sizes service to total facility demand, which is higher. Always confirm which figure a quoted megawatt number refers to before comparing sites. Read the guide →Facilities
Curtailment and firm capacity: Curtailment is a required reduction in a customer’s electricity use, or a generator’s output, ordered by the utility or grid operator during constraints or emergencies. Firm capacity is service the provider commits to deliver without interruption except in rare emergencies. Some large-load arrangements offer faster or cheaper service in exchange for agreed curtailment, which affects how much on-site backup a data center needs. Read the guide →Power

D

Dark fiber: Dark fiber is optical fiber leased or owned without transmission equipment attached, so the customer lights it with its own optics and controls capacity and routing. Lit services, by contrast, are bandwidth sold by a carrier over fiber it lights and manages, such as wavelengths or Ethernet. Large campuses often want dark fiber pairs on diverse routes, while smaller users frequently buy lit services. Read the guide →Water, gas & fiber
Data hall: A data hall is the room inside a data center building that holds rows of server racks, along with the cooling distribution and power distribution that serve them. Buildings usually contain several halls, each with its own electrical and mechanical support spaces nearby. Hall size and count, multiplied by rack density, drive the building footprint and the power the site must eventually deliver. Read the guide →Facilities
Development agreement: A development agreement is a contract between a developer and a local government that sets the terms for a project, such as permitted uses, phasing, infrastructure commitments, fees and how long the rules are locked in. For data center campuses built over many years, it can add certainty that later code changes will not apply. State enabling law determines what such agreements may cover. Read the guide →Permitting
Due diligence period: A due diligence period, often called a feasibility or inspection period, is the window in a land contract during which the buyer investigates the property and can usually terminate without penalty. For data center land, it covers power availability, title, survey, environmental, zoning and utility questions. Its length, extension rights and deposit terms are negotiated, and complex power studies often need extensions. Read the guide →Deals & diligence

E

Easement: An easement is a recorded right that lets someone other than the landowner use part of a property for a specific purpose, such as a pipeline, power line, road or drainage. Easements usually run with the land and survive a sale. On data center sites they can block building footprints, restrict grading, or limit where substations and fiber routes can go, so their exact location and terms matter. Read the guide →Deals & diligence
Edge data center: An edge data center is a smaller facility placed close to end users or devices to reduce latency and backhaul traffic. Edge sites commonly range from about 1–10 MW on 1–10 acres and may connect at distribution voltage. Their siting priorities lean toward metro location, fiber access and zoning compatibility with nearby uses, rather than the large power and land needs of hyperscale campuses. Read the guide →Facilities
Emergency planning zone (EPZ): An emergency planning zone is the area around a nuclear power plant for which emergency response plans are required under federal nuclear regulation. Large reactors have historically used a plume exposure zone of about 10 miles and an ingestion zone of about 50 miles, while smaller reactor designs may justify smaller zones. A data center near a reactor must account for these plans in its siting and operations. Read the guide →Power
ESA Section 7 consultation: Section 7 of the Endangered Species Act requires federal agencies to consult with the U.S. Fish and Wildlife Service or NOAA Fisheries when an action they fund, permit or carry out may affect listed species or critical habitat. A data center triggers it through a federal nexus, such as a Section 404 permit. Projects without a federal nexus still must avoid unlawful take of listed species. Read the guide →Environmental
Evaporative cooling: Evaporative cooling removes heat by evaporating water, either directly into the airstream or through cooling towers and adiabatic coolers. It uses less electricity than mechanical chilling in many climates but consumes water, which raises WUE. For site selection it shifts the focus to water supply, quality, discharge options and drought risk, and it works best where humidity is moderate. Read the guide →Facilities

F

Feasibility study: A data center feasibility study is a structured assessment of whether a specific site can support a planned data center, and under what conditions. It typically covers power, water, gas, fiber, zoning, environmental constraints, buildable area, title and schedule, and identifies the issues that would stop or delay the project. A good study ends with clear findings and what it would take to resolve open items. Read the guide →Deals & diligence
Form 7460-1 and FAA Part 77: FAA Form 7460-1, the Notice of Proposed Construction or Alteration, is filed under 14 CFR Part 77 when a structure or crane would exceed certain heights, such as 200 feet above ground level, or penetrate imaginary surfaces near airports. The FAA studies the filing and issues a determination of whether the structure is a hazard. Stacks, buildings and construction cranes can all require notice. Read the guide →Permitting
Front-of-the-meter (FTM): Front-of-the-meter describes generation, storage or service connected on the utility or grid side of the customer’s meter, where power flows through the regulated system before reaching the load. A data center served front-of-the-meter buys power from the grid under a utility tariff or market arrangement. It is the standard model, and it ties the site’s timeline to grid interconnection and upgrades. Read the guide →Power
Frontage: Frontage is the length of a property’s boundary that adjoins a public road or right-of-way. It determines how many access points a site can have, whether heavy construction and equipment deliveries can reach it, and whether separate secure entrances are possible. Local codes often set minimum frontage and driveway spacing, and limited or landlocked frontage can require new easements or road improvements. Read the guide →Land

G

Gas lateral: A gas lateral is a pipeline branch that carries natural gas from a transmission pipeline or local distribution main to a specific customer site. Data centers planning on-site generation or bridge power often need a dedicated lateral sized for their peak fuel use. Its route, required easements, pressure, metering and who pays for construction are key questions when evaluating gas access. Read the guide →Water, gas & fiber
Geotechnical investigation: A geotechnical investigation is a study of subsurface soil, rock and groundwater conditions, usually based on borings, test pits and lab testing, that informs foundation design and earthwork. For data centers, it checks bearing capacity, shallow rock, expansive or soft soils, karst, groundwater depth and seismic site class. Findings can change grading costs, foundation types and where heavy equipment can sit. Read the guide →Environmental
Gross vs. buildable acreage: Gross acreage is the total deeded or surveyed area of a parcel, while buildable acreage is what remains for buildings, substations and yards after subtracting wetlands, floodplain, steep slopes, easements, setbacks, buffers and stormwater areas. Buildable acreage is often far smaller than gross. For data centers, the shape and contiguity of the remaining land matter as much as the total. Read the guide →Land
Ground lease: A ground lease is a long-term lease of land, usually for decades, under which the tenant builds and owns improvements while the landowner keeps title to the ground. It lets a landowner earn income without selling and lets a developer avoid the upfront land purchase. Term length, rent escalation, financing provisions and what happens to improvements at expiration are central negotiation points. Read the guide →Deals & diligence

H

Hyperscale: Hyperscale refers to the very large data centers and campuses built by companies operating cloud and internet services at massive scale. Hyperscale campuses commonly range from about 100–500 MW on 150–600 acres, with AI-focused campuses reaching higher. They prioritize large, expandable power, contiguous land, water strategy and entitlement certainty, and they typically take service from high-voltage transmission through dedicated substations. Read the guide →Facilities

I

Interconnection: Interconnection is the process and physical connection by which a new load or generator is joined to the electric grid. For a large data center it includes applying to the utility or grid operator, completing load and system studies, agreeing on upgrades and costs, and building the substation and lines that connect the site. It is often the longest item on a data center schedule. Read the guide →Power
IOU, co-op and municipal utility: An investor-owned utility (IOU) is a privately owned, shareholder-funded utility regulated by a state commission. An electric cooperative is owned by its members and often buys power through a generation and transmission co-op. A municipal utility is owned by a city or town. The type affects who sets rates, how large loads are approved and how quickly a utility can commit capacity. Read the guide →Power
ISO/RTO (independent system operator / regional transmission organization): An ISO or RTO is an independent organization that operates the high-voltage grid and runs wholesale electricity markets across a region, under oversight from FERC except in ERCOT. Examples include PJM, ERCOT, MISO, SPP, CAISO, NYISO and ISO-NE. Whether a site sits inside one, and which one, shapes market design, transmission planning and how large-load interconnection works. Read the guide →Power

J

Jurisdictional determination (JD): A jurisdictional determination is a U.S. Army Corps of Engineers document stating whether wetlands or waters on a site are regulated under the Clean Water Act. An approved JD is a formal, appealable finding, while a preliminary JD treats the features as potentially jurisdictional. Securing one clarifies what can be filled, what needs a Section 404 permit, and how much land is truly buildable. Read the guide →Environmental

K

kV (kilovolt): A kilovolt is one thousand volts, the unit used to describe power line and substation voltages. Common U.S. transmission voltages are 69, 115, 138, 161, 230, 345, 500 and 765 kV, while distribution usually runs below about 35 kV. Higher voltage lines can generally carry more power over longer distances, so large data centers usually seek access to higher-voltage transmission. Read the guide →Power

L

Latency: Latency is the time it takes data to travel between two points on a network, usually measured in milliseconds round trip. In fiber, light travels roughly five microseconds per kilometer one way, so route distance, not straight-line distance, sets the floor. Latency matters most for edge, colocation and interactive workloads, and less for training or batch workloads that can sit far from users. Read the guide →Water, gas & fiber
Liquid cooling (direct-to-chip and immersion): Liquid cooling removes heat from IT equipment with a fluid rather than air alone, allowing much higher rack densities. Direct-to-chip cooling pumps coolant through cold plates attached to processors, while immersion cooling submerges servers in a dielectric fluid. Both change building design, floor loading and heat rejection, and they can lower water use when paired with closed-loop systems and dry coolers. Read the guide →Facilities
Load factor: Load factor is the ratio of a customer’s average electricity demand to its peak demand over a period, expressed as a percentage. Data centers run close to their peak most of the time, so they have high load factors compared with most commercial users. Utilities value that steady demand, but it also means the grid must supply nearly full capacity around the clock. Read the guide →Power
Load study, system impact study and facilities study: Load, system impact and facilities studies are the utility or grid operator analyses that define how a new large load gets served. A load study is the initial review of whether and how a site can be served. A system impact study tests grid effects and identifies needed upgrades. A facilities study specifies the equipment, cost estimates and schedule. Names, sequence and scope vary by utility, and results set the real power timeline. Read the guide →Power
LOMA (Letter of Map Amendment): A Letter of Map Amendment is a FEMA determination that a specific property or structure, on natural ground, sits above the Base Flood Elevation and is therefore removed from the special flood hazard area. It relies on surveyed elevations. Where fill has raised the ground, a different process, the LOMR-F, applies. A LOMA changes insurance and regulatory status but not the physical flood risk. Read the guide →Environmental
Long-haul and metro fiber: Long-haul fiber is network cable that connects cities and regions over hundreds of miles, typically along highways, railroads or pipeline corridors. Metro fiber is the denser network within a metropolitan area that links buildings, carrier hotels and data centers. A remote campus usually needs a lateral to nearby long-haul routes, while metro fiber matters most for colocation and edge sites. Read the guide →Water, gas & fiber

M

Microgrid: A microgrid is a local group of generation, storage and loads with its own controls that can operate connected to the main grid or separately in island mode. For a data center, a microgrid might combine on-site generation, batteries and utility service to improve resilience or allow early operation. Its design affects air permits, fuel supply, interconnection terms and how utility rules treat the site. Read the guide →Power
Mineral rights: Mineral rights are ownership rights to oil, gas, coal or other minerals beneath a property, which can be severed from the surface and owned by someone else. A severed mineral owner may have rights to use the surface for extraction, depending on state law and the deed. On data center land, title review should identify severed minerals and any surface use protections or accommodations. Read the guide →Deals & diligence
Moratorium: A moratorium is a temporary local or state pause on accepting or approving certain applications, such as new data centers, while officials study impacts or rewrite rules. It can stop an otherwise viable project for months or longer and often signals stricter standards to come. Screening a site includes checking for adopted moratoriums, pending proposals and public debate in the jurisdiction. Read the guide →Permitting
MW (megawatt): A megawatt is one million watts, the unit used to size data center power demand and generation. Data center capacity may be quoted as MW of critical IT load or as total facility demand including cooling, which is higher, so the basis should always be stated. Edge sites run about 1–10 MW, while hyperscale campuses commonly range from 100–500 MW or more. Read the guide →Power

N

N+1 redundancy: N+1 redundancy means a system has the number of components needed to carry the full load (N) plus one spare, so any single unit can fail or be serviced without losing capacity. It is commonly applied to generators, UPS modules, chillers and cooling units. N+1 protects against one component failure but not against failure of a shared path, which is where 2N designs differ. Read the guide →Facilities
NEPA (National Environmental Policy Act): The National Environmental Policy Act requires federal agencies to evaluate the environmental effects of their actions before deciding, through a categorical exclusion, environmental assessment or environmental impact statement. A private data center triggers NEPA only with a federal nexus, such as federal funding, federal land or a federal permit. When triggered, the review can add significant time to the schedule. Read the guide →Environmental
Network upgrade: A network upgrade is an improvement to the shared transmission system, such as a new line, rebuilt substation or larger transformer, needed to serve a new load or generator reliably. Unlike facilities that serve only the customer, network upgrades benefit the broader grid. Who pays for them, and whether costs are credited back over time, depends on the utility, grid operator and regulatory rules. Read the guide →Power
NPDES permit and SWPPP: The National Pollutant Discharge Elimination System is the Clean Water Act permit program for discharges to surface waters, including construction stormwater from sites disturbing one acre or more. Coverage under a construction general permit requires a stormwater pollution prevention plan, or SWPPP, describing erosion controls, inspections and practices on site. Many states administer the program with their own requirements. Read the guide →Environmental

O

Option agreement: An option agreement gives a buyer the exclusive right, but not the obligation, to purchase land at agreed terms within a set period, in exchange for an option payment to the owner. Data center developers use options to control land while they study power and entitlements. Key terms include the option period, extension payments, whether payments apply to the price, and access rights for diligence. Read the guide →Deals & diligence

P

Phase I ESA (environmental site assessment): A Phase I environmental site assessment is a non-invasive review of a property’s current and past uses to identify recognized environmental conditions, performed to the ASTM E1527-21 standard. It includes records research, a site visit and interviews. A compliant Phase I supports landowner liability protections under federal law, and its findings decide whether sampling in a Phase II is warranted. Read the guide →Environmental
Phase II ESA: A Phase II environmental site assessment is an investigation that samples soil, groundwater, soil vapor or building materials to test whether contamination suspected in a Phase I is actually present, and at what levels. It is commonly guided by ASTM E1903. Results inform cleanup needs, regulatory reporting, cost and whether a site such as a brownfield remains practical for a data center. Read the guide →Environmental
PILOT (payment in lieu of taxes): A payment in lieu of taxes is an agreement under which a project makes negotiated payments to a local government instead of, or in place of part of, normal property taxes. For data centers, PILOTs are often used to provide predictable tax costs over many years in exchange for investment and jobs. Availability, structure and approval steps vary by state and locality. Read the guide →Permitting
Powered land: Powered land is a site where substantial electric capacity is already available or contractually committed, with a clear path to energization, rather than land that merely sits near power lines. True powered land has a utility commitment, defined MW, a timeline and a substation plan. It typically commands a premium because power is usually the longest lead item for a data center. Read the guide →Power
PPA and virtual PPA: A power purchase agreement is a long-term contract to buy electricity, often from a specific generator, at agreed prices. In a physical PPA the power is delivered to the buyer’s load. In a virtual PPA the buyer and generator settle the difference between a fixed price and the market price, and the buyer usually receives the renewable energy certificates, without physical delivery. Read the guide →Power
PSD and Title V air permits: Prevention of Significant Deterioration is the Clean Air Act preconstruction permit program for new or modified major emission sources in areas meeting air quality standards. Title V is the operating permit program for major sources. Large banks of data center generators can approach major-source thresholds, so developers often accept limits on run hours to stay below them. Most programs are administered by state agencies. Read the guide →Permitting
PUE (power usage effectiveness): Power usage effectiveness is the ratio of a data center’s total facility energy to the energy used by its IT equipment, a metric developed by The Green Grid. A PUE of 1.0 would mean all energy goes to IT, and higher values show more overhead for cooling and power losses. Climate and cooling design strongly affect PUE, so it influences site selection. Read the guide →Facilities
Purchase and sale agreement (PSA): A purchase and sale agreement is the binding contract in which a buyer agrees to buy and a seller agrees to sell real property on stated terms. For data center land it sets price, deposits, the due diligence period, closing conditions such as power or zoning approvals, and title and survey requirements. Contingencies tied to utility commitments are common and heavily negotiated. Read the guide →Deals & diligence

R

Rack density: Rack density is the amount of power drawn by the IT equipment in a single server rack, usually stated in kilowatts per rack. Higher densities pack more computing into less floor area but concentrate heat, often requiring liquid cooling. For site planning, density affects building size, cooling method and water needs, though total campus power, not floor area, usually remains the main constraint. Read the guide →Facilities
Ramp schedule: A ramp schedule is the planned timeline showing how a data center’s electric demand grows from first energization to full load, usually stated in MW by year or quarter. Utilities use it to plan substations, transmission upgrades and generation. A realistic ramp schedule can speed service for early phases, and it often becomes part of the electric service agreement and its minimum bill terms. Read the guide →Power
REC (renewable energy certificate): A renewable energy certificate is a tradable instrument representing the environmental attributes of one megawatt-hour of electricity generated from a renewable source. Buyers retire RECs to support claims of renewable energy use. RECs can be bundled with power or sold separately. In environmental diligence, REC also means recognized environmental condition, a different term used in Phase I reports. Read the guide →Power
Reciprocating engine vs. combustion turbine: A reciprocating engine is a piston engine, fueled by diesel or natural gas, that drives a generator, while a combustion turbine burns fuel to spin a turbine directly. Engines are modular, start quickly and are common for backup and bridge power. Turbines offer more output per unit and suit larger continuous loads. Fuel supply, emissions, noise and redundancy drive the choice. Read the guide →Power
Resource adequacy: Resource adequacy is the ability of a power system to have enough generation, storage and demand response available to meet expected peak demand with a planned reserve margin. Grid operators and state regulators manage it through capacity markets, utility planning or obligations on load-serving entities. Large new data center loads increase the resources a region must secure, which can affect service timelines. Read the guide →Power
Rezoning: Rezoning is a legislative change to the zoning district that applies to a property, usually requiring public hearings before a planning commission and a vote by the governing body. Data center sites often need rezoning from agricultural or residential districts to an industrial or special district. It is discretionary, can draw public opposition and may carry conditions such as setbacks, noise limits or screening. Read the guide →Permitting
Ride-through: Ride-through is the ability of electrical equipment, or an entire facility, to stay connected and operating during brief voltage or frequency disturbances on the grid instead of disconnecting. When many data center loads trip off at once, the sudden loss of demand can stress the grid. Utilities and grid operators may set ride-through requirements for large loads as a condition of service. Read the guide →Power
Rollback taxes: Rollback taxes are a recapture of property tax savings owed when land assessed at a reduced agricultural, forestry or open-space value is converted to another use, such as a data center. The amount usually reflects the difference between preferential and market-based taxes for a set number of prior years, sometimes with interest. Rules and who pays vary by state and by contract. Read the guide →Deals & diligence
Route diversity: Route diversity means having two or more fiber paths into and away from a site that follow physically separate routes, so a single cut, fire or construction accident cannot sever all connectivity. True diversity requires separate conduits, entrances and ideally separate carriers and long-haul corridors. Shared bridges, rail rights-of-way or a single road in can undermine paths that appear diverse on paper. Read the guide →Water, gas & fiber

S

Sales tax exemption: A data center sales tax exemption waives or reduces state and sometimes local sales and use tax on qualifying purchases, such as servers, network gear and electrical and cooling equipment. Because equipment is refreshed often, this incentive can matter more over a project’s life than property tax relief. Eligibility thresholds for investment, jobs and wages vary by state and can change. Read the guide →Permitting
Section 106 review: Section 106 of the National Historic Preservation Act requires federal agencies to consider the effects of their actions on historic properties and archaeological sites, in consultation with the State Historic Preservation Office and tribes. A data center triggers it through a federal nexus, such as a Section 404 permit. A cultural resources survey identifies sites that may need avoidance or mitigation. Read the guide →Environmental
Section 404 permit: A Section 404 permit, issued by the U.S. Army Corps of Engineers under the Clean Water Act, authorizes placing fill material in regulated wetlands and waters. Small impacts may fit a nationwide permit, while larger impacts need an individual permit with more review. Avoiding wetlands in the site layout usually saves time, and a 404 permit can create a federal nexus for other reviews. Read the guide →Environmental
Setback and buffer: A setback is the minimum required distance between a structure, or equipment such as generators, and a property line, road or neighboring use. A buffer is an area kept as open space or landscaping, often with berms or walls, to separate a facility from neighbors. Data center codes increasingly tie both to noise and visibility, and the required distances vary by jurisdiction. Read the guide →Land
SFHA (special flood hazard area): A special flood hazard area is land that FEMA maps as subject to the 1% annual chance flood, often called the 100-year floodplain, shown on Flood Insurance Rate Maps as Zone A, AE and related zones. Zone AE is the part where FEMA has determined Base Flood Elevations. Building in an SFHA triggers floodplain permitting, elevation requirements and flood insurance requirements for federally backed loans. Read the guide →Environmental
SMR (small modular reactor): A small modular reactor is a nuclear reactor design with a smaller output per unit than conventional plants, commonly defined as up to roughly 300 MW electric, and built largely from factory-made modules. SMRs are discussed as a future power source for large data center campuses. Siting depends on federal licensing, emergency planning zone requirements, cooling water, geology and population distance. Read the guide →Power
Substation: A substation is a facility of transformers, breakers and switching equipment that changes voltage and routes power between transmission and distribution lines or to a customer. A large data center usually needs its own substation, or a dedicated expansion of an existing one, to step transmission voltage down for the site. Available transformer capacity at nearby substations is a primary power screen. Read the guide →Power
Switchyard: A switchyard is an outdoor arrangement of circuit breakers, switches and buswork, operating at transmission voltage, that connects lines together or ties a facility into the grid without necessarily changing voltage. For data center campuses, the utility often owns a switchyard where the transmission line terminates, next to a customer substation that steps voltage down. Both need land, access and line routes. Read the guide →Power

T

Title commitment: A title commitment is a title insurer’s written offer to issue a policy on a property, listing the current owner, the requirements to close, and the exceptions the policy will not cover, such as recorded easements, liens and restrictions. For data center land, reviewing each exception against the survey shows which recorded rights could affect buildable area, access or utility routes. Read the guide →Deals & diligence
Transformer: A transformer is electrical equipment that raises or lowers voltage by electromagnetic induction. Large power transformers step transmission voltage down at a data center substation, and smaller units step it down again inside the campus. High-voltage power transformers are custom-built and can have long manufacturing lead times, so their availability often affects energization schedules. Read the guide →Power
Transmission line vs. distribution line: A transmission line is a high-voltage power line, commonly 69 kV and above in the U.S., that moves bulk electricity from power plants to substations. A distribution line runs at lower voltage, typically below about 35 kV, and delivers power from substations to local customers. Large data centers usually need transmission service through a dedicated substation, while distribution service suits edge sites and small loads. Read the guide →Power

U

Uptime Institute Tier (I–IV): The Uptime Institute Tier classification is a four-level standard for data center infrastructure topology, from Tier I basic capacity to Tier IV fault tolerant. Tier III requires concurrent maintainability, meaning any component can be serviced without shutting down IT. Tier ratings describe the building’s design and operations, not the site, but higher tiers raise expectations for redundant utility feeds and backup power. Read the guide →Facilities
Utility service territory: A utility service territory is the geographic area in which a particular utility has the right, and often the obligation, to provide service, typically assigned by state regulators. It determines which electric, gas or water provider a site must work with. Territory boundaries, especially between co-ops, municipal utilities and investor-owned utilities, can sit close to a site and change its power options. Read the guide →Power

W

WUE (water usage effectiveness): Water usage effectiveness is a metric developed by The Green Grid that divides a data center’s annual site water use by the energy used by its IT equipment, expressed in liters per kilowatt-hour. Lower values mean less water consumed per unit of computing. Cooling design and climate drive WUE, and it is often weighed against PUE because water-saving cooling can use more energy. Read the guide →Facilities

Z

Zone X (flood zone): Zone X is a FEMA flood zone designation for areas outside the 1% annual chance floodplain. Shaded Zone X marks areas of moderate hazard, including the 0.2% annual chance or 500-year floodplain, while unshaded Zone X marks minimal flood hazard. Zone X land is generally outside federal flood insurance mandates, but local stormwater and drainage conditions still deserve review for critical facilities. Read the guide →Environmental