Large Load Tariffs Are Redrawing the Site Selection Map
For most of the last decade, data center site selection came down to a familiar checklist: land, fiber, water, and above all, power. Find a substation with headroom, get in the queue, and build. That checklist now has a new line item. Across the country, utilities are rolling out large load tariffs, special rate schedules that dictate how data centers and other high-demand customers connect, what they pay, and how hard it is to walk away.
The pace is striking. State regulators approved 29 large load tariffs in 2025 alone, compared with 14 over the previous seven years combined, according to the Smart Electric Power Alliance. And the terms vary widely. One utility may require a 12-year commitment and two years of minimum bills as collateral, while a neighboring utility has no special requirements at all.
The result is a site selection map that no longer follows the grid alone. Two parcels with similar substation access can carry very different contract terms, collateral requirements, and exit costs depending on which utility serves them. LandGate maps utility service territories alongside substations, transmission, and existing and proposed data center sites, so developers can see those boundaries at the parcel level before they commit.
What Is a Large Load Tariff?
A large load is a single customer, or a cluster of related customers, whose electricity demand is big enough to change how a utility plans its grid. While advanced manufacturing and hydrogen production fall into this category, data centers and AI hyperscale campuses demanding anywhere from 25 MW to over a gigawatt are the primary drivers.
A large load tariff is the rate schedule and set of service rules a utility applies to those customers. The purpose of a large load tariff is to solve stranded asset risk. Serving a multi-hundred-megawatt data center often requires tens or hundreds of millions of dollars in network upgrades, new substations, transformers, and distribution lines. If a project gets delayed, downsized, or abandoned mid-stream, traditional ratepaying homeowners and businesses risk being left with the bill for unused infrastructure. Large load tariffs shift that risk back onto the developer.
There is no single national definition of a large load. Federal proposals have used 20 MW, FERC's June 2026 orders floated 50 MW, ERCOT uses 75 MW, and individual utility tariffs start anywhere from 5 MW to 100 MW or more. Nearly every large load tariff is built from the same handful of components. These are the ones with the biggest effect on project economics:
Size threshold: the load size, sometimes aggregated across nearby facilities, that triggers the tariff.
Minimum billing: a floor on monthly demand charges, usually a percentage of contracted capacity, paid whether or not the load uses it.
Contract term and ramp: how long the customer must commit, often after a multi-year ramp-up period.
Collateral: financial security posted up front to protect the utility if the project falls short.
Exit terms: notice periods and fees for downsizing or terminating service.
Upgrade cost allocation: whether the customer pays directly for the network upgrades its load requires.
Minimum billing and collateral deserve the most attention during site selection. A high minimum bill means a campus that ramps slower than planned pays for capacity it isn't using. Collateral tied to upgrade costs means a site that needs a new substation ties up far more capital before it produces revenue than a site with existing headroom.
Large Load Tariffs by Grid Region
Large load rules work on two levels. Grid operators (RTOs and ISOs) set the transmission-level study and service process, while the local utility serving the site sets the retail tariff terms. Both are changing fast. On June 18, 2026, FERC issued show cause orders directing organized market operators to justify or reform their large load interconnection rules, so expect more changes over the next year.
Here's how a few approved and model tariffs compare:
Utility or framework | Threshold | Minimum billing | Contract term |
AEP Ohio (PJM) | 25 MW | 85% of subscribed capacity | Up to 12 years, including 4-year ramp |
Dominion Energy Virginia (PJM) | 25 MW | 85% of T&D demand, 60% of generation demand | Effective January 2027 |
Pennsylvania model tariff (PJM) | 50 MW individual / 100 MW aggregate | 80% of contracted capacity | 5 years after a 3–5 year ramp |
Missouri SB 4 tariffs (MISO and SPP) | Varies by utility | 80% demand charge | 12 years plus optional 5-year ramp |
Evergy Kansas (SPP) | 75 MW | 80% of contract demand | 12 years after up to 5-year ramp |
PJM
PJM is home to the nation’s most mature large load tariffs, driven by heavy data center density in Northern Virginia, Ohio, and Pennsylvania. AEP Ohio’s approved data center tariff mandates that new customers above 25 MW pay for at least 85% of subscribed capacity for up to 12 years. In Virginia, Dominion Energy’s GS-5 rate class sets minimum demand charges at 85% for transmission and distribution and 60% for generation. Pennsylvania finalized a model tariff allowing utilities like PPL to enforce 10-year commitments.
MISO
MISO’s large load landscape is undergoing rapid transformation following FERC directives ordering clearer study processes for loads above 50 MW. At the state and utility level, variation is high. For example, under Missouri's SB 4 framework, utilities like Ameren Missouri require 12-year contract terms, two years of minimum monthly bills posted as upfront collateral, and a 24-month exit notice. Siting data centers and other large loads in MISO requires mapping sub-regional utility tariffs alongside transmission constraints.
ERCOT
Operating outside FERC’s federal jurisdiction, Texas regulates large loads through state law and ERCOT market protocols rather than individual utility rate classes. The Public Utility Commission of Texas (PUCT) utilizes a batch study process for loads of 75 MW or greater. Each studied load receives a firm capacity allocation, but developers must carefully map local Transmission and Distribution Utility (TDU) service territories - such as Oncor, CenterPoint, or AEP Texas - to evaluate regional grid capacity and localized interconnection rules.
SPP
SPP offers abundant land and low-cost renewable power, making it an increasingly attractive target for large-scale data center campuses. However, navigating SPP requires managing both regional transmission upgrade cost allocations and state-specific utility tariffs. For instance, Evergy Kansas enforces a 75 MW large load tariff requiring an 80% demand bill floor over a 12-year contract term. Crossing utility boundaries within SPP can significantly alter project balance sheet risks.
CAISO
California's approach centers on who pays up front. PG&E's proposed Rule 30, which would govern transmission-level connections for large loads, has been operating under interim CPUC approval since July 2025. Under that approval, customers pay up front for the transmission infrastructure they need. Recent project-specific approvals in San Jose capped refunds at 75% of the revenue PG&E collects from the customer and stretched the refund period to 15 years. Developers should watch for the CPUC's final Rule 30 decision, which will settle refund terms statewide for PG&E territory.
NYISO
NYISO faces a structural split between downstate load demand and upstate power generation. Large load data center development is shifting heavily upstate toward clean hydropower and nuclear generation hubs. Siting effectively in NYISO requires mapping local utility rate tariffs, evaluating economic power incentives (such as ReCharge NY), and analyzing localized grid constraints to ensure capacity can actually be delivered.
Why Large Load Tariffs Belong in Site Screening
Power availability still comes first: substation proximity, hosting capacity, and queue position. But large load tariffs now shape the economics of a site almost as much as the grid does. Four questions belong in every early screen:
Which utility serves this parcel? Service territory boundaries don't follow county or state lines, and a site a few miles from another candidate can fall under a completely different tariff.
How much new infrastructure will this site need? Where customers pay directly for upgrades and post collateral to cover them, sites with existing headroom keep capital free.
What's nearby? Aggregation rules can pull neighboring facilities and your own future phases into a tariff, and nearby large loads compete for the same capacity.
Can onsite generation or flexibility change the math? Several frameworks reward loads that bring their own generation or accept non-firm service, which can open sites that firm service alone can't.
Answering these questions after a site is under contract is expensive. Answering them during screening lets developers rank sites by total cost to serve, not just distance to a substation.
How LandGate Solves the Large Load Site Selection Challenge
LandGate brings the data behind these questions into one map, so developers can screen for tariff exposure alongside grid capacity:
Utility service territories show exactly which utility serves each parcel, so you know whose large load tariff applies before running any numbers.
Substations and subtransmission data, including hosting capacity and available transfer capability, help identify sites that may need fewer upgrades and less collateral.
Existing and proposed data center sites reveal nearby large loads that could affect aggregation and competition for capacity.
Proposed transmission lines and the interconnection queue show where the grid is headed and where capacity is already spoken for.
Natural gas pipeline and offtake data support behind-the-meter generation analysis for sites where onsite supply could reduce grid demand.
Transmission planning models across all major ISOs and RTOs add context on where regional upgrades are planned.
Together, these layers let a development team move from "Is there power here?" to "What will it cost us to take power here, and under whose rules?"
Developers who screen for tariff terms early will spend less capital on the wrong sites. By combining utility territory mapping, parcel-level constraints, and power grid analytics into a single tab, LandGate empowers data center teams to rule out non-viable parcels instantly and commit capital only to sites with clear paths to power and favorable tariff economics.
