--- title: "Interconnection Voltage for Data Centers: What 69 kV, 138 kV, and 230 kV Mean for a Site | Insights | Build" description: "Interconnection voltage is the voltage at which a data center connects to the utility grid. Lower voltage connects faster and costs less but caps how many megawatts a site can ever draw. Higher voltage supports larger campuses but usually means a customer-owned substation and a longer study and equipment timeline. Size the voltage to full buildout, not phase one, and confirm the exact line and substation, not just the voltage class." url: https://build.inc/insights/data-center-interconnection-voltage-level-site-selection --- [Technology](https://build.inc/insights?category=technology) # Interconnection Voltage for Data Centers: What 69 kV, 138 kV, and 230 kV Mean for a Site Interconnection voltage is the voltage at which a data center connects to the utility grid. Lower voltage connects faster and costs less but caps how many megawatts a site can ever draw. Higher voltage supports larger campuses but usually means a customer-owned substation and a longer study and equipment timeline. Size the voltage to full buildout, not phase one, and confirm the exact line and substation, not just the voltage class. by Build Team • November 6, 2026 • 6 min read ## The short answer Interconnection voltage is the voltage at which a data center connects to the utility grid. It decides how many megawatts a site can ever draw, who owns the substation, and how long energization takes. The rule that avoids the most expensive mistake is simple: match the voltage to the megawatts you need at full buildout, not the megawatts you need on day one. ## What interconnection voltage means Utilities group their lines into voltage classes. Labels and cutoffs vary by utility and region, so treat the ranges below as general orientation and confirm with the serving utility. - **Distribution** lines carry power at lower voltages and feed neighborhoods, commercial parks, and small loads. - **Subtransmission** lines, often around 69 kV, link distribution substations to the larger grid. - **Transmission** lines, commonly 115 kV, 138 kV, 230 kV, 345 kV and above, move bulk power over distance. A data center connects at the class that matches its load. The bigger the load, the higher the voltage the utility will require, because higher voltage moves more power with less current and fewer losses. ## How the voltage class changes the site Voltage class Where it usually fits What it means for the site Main risk Distribution feeder Edge sites and small early phases Utility often owns the equipment and the connection is quicker Feeder capacity may already be spoken for by neighbors, and the ceiling is low Subtransmission (for example 69 kV) Mid-size campuses A customer substation is likely, with a dedicated line tap Line loading and upgrade scope can surprise you late Transmission (for example 138 kV and above) Large AI and hyperscale campuses Customer substation, breakers, protection, and a formal utility study Longer study queue and long-lead transformer and breaker procurement ## Five decision rules 1. **Size to full buildout.** A site that works at one voltage for phase one but needs a higher class for phase two is a different site. Ask the utility what it would take to move up a class later. 2. **Ask which line and which substation, not just which voltage.** A transmission line crossing the parcel is not a tap. The utility decides where, and whether, a connection is allowed. 3. **Price the step-up.** If the nearby line is lower voltage than your load needs, the cost and time to bring in a higher class belongs in the underwriting, not in a footnote. 4. **Check redundancy.** Single-circuit and double-circuit service carry different outage risk. Match it to the uptime your tenant expects. 5. **Tie voltage to equipment lead time.** Higher classes pull in larger transformers and switchgear. Confirm the procurement timeline before you treat an energization date as real. ## Questions to put to the utility - At what voltage will you serve this load, and at which substation or line? - What is the load size at which the voltage class changes? - Who owns and builds the substation, and who pays for upgrades? - Is the study complete, in progress, or not started for this site? - What happens to the voltage requirement if we add a second phase? ## What the client gets Build sources the sites, then validates them against the checks that would kill a deal, including the serving voltage, the named substation, and the study stage. The client sees which sites can carry full buildout at a credible date, and Build bundles the utility coordination and engineering services needed to close the gaps on the ones worth pursuing. ## Frequently Asked Questions: What is interconnection voltage for a data center? It is the voltage at which the data center connects to the utility grid. It determines the maximum load the site can draw, the equipment required, and who typically owns the substation. Is higher interconnection voltage always better? No. Higher voltage supports more megawatts but usually requires a customer substation, a longer study, and long-lead equipment. A smaller or phased project can be better served by a lower class that connects faster. Does a transmission line next to a site mean I can connect to it? No. The utility decides where and whether a tap is allowed, based on its own studies and capacity. Proximity alone proves nothing. Who decides the voltage a data center is served at? The serving utility sets the requirement based on load size and its system. Confirm it in writing early in the process. How should I handle phase two at a site? Ask the utility now what voltage and upgrades full buildout requires, and price any step-up into the underwriting before committing. 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