Large-Load Tariffs and Electric Service Agreements, Explained

A tariff is a utility’s published schedule of rates, charges and conditions of service, approved by its regulator. Investor-owned utilities file tariffs with a state public utility commission. Municipal utilities and cooperatives set rates through their own governing bodies, sometimes with state oversight. Most utilities have a general tariff for large commercial and industrial customers, and a growing number have provisions written specifically for very large loads such as data centers.

The electric service agreement (ESA) is the contract between the utility and one customer. It applies the tariff to a specific site and load, and fills in project details: the ramp, contract demand, facilities to be built, who pays for them, security, term and what happens if plans change. Some ESAs follow the tariff closely. Others, especially for the largest loads, are negotiated special contracts that may need regulatory approval of their own.

The ESA usually comes after the load studies in the large-load interconnection process. It is the point where the utility’s cost and capacity commitments, and the customer’s financial commitments, become binding.

Not every agreement uses all of these, and the same term can work differently from one utility to the next. A minimum bill might be a share of contract demand at one utility and a fixed charge tied to unrecovered investment at another.

Contract demand is the center of the agreement. It is the capacity the utility plans and builds for, and it usually follows the project’s load ramp schedule. If the campus is planned to reach 150 MW in year three, contract demand for year three is likely to be near 150 MW.

Minimum bill and take-or-pay provisions exist because utilities and regulators do not want other customers paying for capacity built for a load that never arrives. The customer pays a floor amount tied to contract demand, even if actual demand is lower. For a data center, that means a delay in tenant move-in or a slower fit-out does not reduce the bill as much as it would under a normal tariff.

• Ask what share of contract demand the minimum applies to, and whether it changes over the term.
• Ask whether contract demand can be deferred or reduced with notice, and at what cost.
• Ask whether the minimum covers only demand charges or energy and other charges as well.
• Model the minimum bill against a slow-ramp case, not only the base case.

Collateral protects the utility if the customer fails to pay or walks away. It is usually sized to the utility’s unrecovered investment or to a set number of months of minimum bills, and it may step down as the load ramps and the utility recovers its costs. Customers with strong credit ratings may be able to substitute parent-company credit support for cash or a letter of credit. Project-level entities without that credit often post more.

CIAC is different. It is a payment for facilities that are built mainly to serve the customer: the line extension to the site, the customer substation, a new switching station or similar. Some utilities require CIAC up front. Others allow the cost to be recovered over time through a facilities charge, or credit part of it back as the load generates revenue. Which facilities count as customer-specific and which as shared network upgrades is a separate question, covered in our guide to transmission upgrades and who pays for them.

Large-load agreements often run longer than a typical commercial service contract. Long terms give the utility time to recover its investment. For the customer, the cost is reduced flexibility: the right to shrink, move or end service usually comes with a fee tied to the utility’s remaining cost.

• Assignment. Can the agreement be assigned to a buyer of the campus, a tenant or a lender?
• Load reductions. Can contract demand be reduced, and with how much notice?
• Delays. What happens if the utility’s facilities are late, and what happens if the customer’s are?
• Changes in law or tariff. Does the agreement follow later tariff changes, or are terms fixed?
• Curtailment and flexibility. Is any part of the load non-firm, and on what conditions can it be interrupted?

Assignment matters more than it seems for land deals. A landowner or developer who signs an early agreement may want to transfer it with the site. Utilities differ on whether that is allowed and what consent it takes.

Tariff terms are often treated as a late-stage legal task. They belong in site comparison. A site with a lower energy rate but heavy minimum bills, high collateral and a long term can be the more expensive choice for a project with an uncertain ramp. Market structure matters too: whether the utility is vertically integrated or the customer buys energy in a competitive market changes which parts of the bill the tariff controls. See ISO and RTO markets and data center siting.

1. 01Identify the utility that would serve each site and whether it has a large-load tariff or uses special contracts.
2. 02Collect its standard terms for contract demand, minimum bills, collateral, CIAC and term.
3. 03Run the project’s base and slow-ramp cases through each set of terms.
4. 04Compare capital committed before first power, not only the energy rate.
5. 05Flag terms that would block assignment or financing.

Large-load tariffs are being revised in many places as utilities respond to data center demand, so treat any set of terms as something to reconfirm close to signing.