Rate Base Implications of Large Load Agreements: A Primer for Utility Accountants

Rate base is the foundation of utility earnings. It represents the net investment in utility plant that regulators have authorized the utility to earn a return on—a return that flows through to rates and ultimately to customers. When a utility signs a large load service agreement and builds the infrastructure to support it, the rate base implications of that investment deserve the same careful analysis as the contractual and operational dimensions.

Yet in the urgency of responding to large load requests, rate base analysis often receives less attention than it deserves. This article provides a systematic overview of the rate base questions that utility accountants should be asking at every stage of a large load agreement—from negotiation through the life of the infrastructure.

What Goes into Rate Base (and What Doesn’t)

Rate base, in its most fundamental form, is net utility plant in service—the gross cost of utility plant less accumulated depreciation, plus certain regulatory adjustments. For large load infrastructure, the key question is which investments qualify for rate base inclusion and earn an authorized return, and which do not.

Infrastructure that is used and useful in providing regulated service generally qualifies for rate base inclusion. For a utility with large load, this typically includes:

• Transmission lines and substations constructed to serve large load
• Distribution upgrades required to meet large load customer service specifications
• Metering and protective relay equipment associated with large load customer service points
• Capitalized overhead costs and allowance for funds used during construction (AFUDC) during the construction period

What does not go into rate base:

• The portion of infrastructure costs funded by customer CIAC (CIAC reduces net plant in rate base)
• Costs that regulators have disallowed or are probable of disallowance
• Costs that are recovered through mechanisms outside rate base (such as pass-through riders that do not earn a return)
• Plant that is no longer used and useful in providing service

Four Rate Base Questions for Data Center Agreements

Question 1

How does CIAC affect the rate base treatment of dedicated infrastructure?

When a large load customer pays a contribution in aid of construction, those funds reduce the utility’s net investment in the infrastructure. For rate base purposes, CIAC-funded infrastructure does not earn a return because the utility has not invested its own capital—the customer has effectively purchased that portion of the infrastructure.

The rate base implication is that infrastructure funded by CIAC does not generate the return on investment that rate-base-funded infrastructure does. Utilities should model the rate base impact of different CIAC levels when evaluating large load agreements, because the return-on-equity component of infrastructure costs is only earned on the net rate base investment, not the gross investment.

This also creates a tension in negotiating CIAC: higher CIAC is better for ratepayer protection (reduces the at-risk rate base investment) but worse for utility earnings (reduces the rate base on which a return is earned). Finding the right balance requires analysis that integrates both the financial protection and the earnings perspectives.

Question 2

Should dedicated large load infrastructure be included in general rate base or tracked separately?

Utilities have choices about how to present dedicated large load infrastructure in their accounting and rate base records. General rate base inclusion pools the infrastructure with all other utility plant and recovers costs through base rates. A separate tracking mechanism ties the infrastructure to specific cost recovery riders or tariff provisions.

The case for separate tracking is strong. When dedicated infrastructure is commingled with general rate base, it becomes difficult to demonstrate the connection between specific assets and specific cost recovery mechanisms, to monitor the adequacy of cost recovery over time, and to identify stranded cost exposure if a customer exits. Regulatory requirements in some jurisdictions mandate separate accounting for large-load customer infrastructure for exactly these reasons.

Utility accounting systems should be configured to track dedicated large load infrastructure as a distinct asset category from the moment capitalization begins, not retrofitted to create this segregation after the fact.

Question 3

What depreciation rates apply to dedicated large load infrastructure?

Depreciation rates for utility plant are typically set by regulatory order based on the estimated service life of the assets. For dedicated large load infrastructure, the appropriate depreciation rate depends on the regulatory classification of the assets and whether special depreciation treatment has been authorized.

As discussed in our article on Stranded Asset Risk in Data Center Agreements, accelerated depreciation aligned with the contract term can significantly reduce stranded cost exposure. But accelerated depreciation requires regulatory approval and results in higher annual depreciation charges during the agreement term. The economics of accelerated depreciation need to be evaluated in the context of the agreement’s minimum bill structure and the utility’s overall rate design.

Utilities entering into large load agreements with terms shorter than the expected physical life of the infrastructure should specifically address depreciation treatment in the regulatory filing associated with the agreement.

Question 4

How does large load infrastructure affect the utility’s overall rate base and earnings outlook?

For a utility with a large large load agreement, the infrastructure investment may represent a material portion of total rate base. This has both upside and downside implications. On the upside, rate base growth supports earnings growth if the infrastructure is properly included in the rate base on which a return is authorized. On the downside, a customer exit that strands a significant portion of rate base can have a material negative impact on earnings.

Utility financial management should assess the sensitivity of earnings to large load agreement performance scenarios. This includes stress-testing the rate base model against scenarios where customers exit early, where infrastructure costs exceed projections, and where regulatory approval of cost recovery is delayed or partial.

Regulatory Update · FERC Docket RM26-4-000

FERC Issued Landmark Large-Load Interconnection Orders on June 18, 2026

On June 18, 2026, FERC voted unanimously to issue tailored show-cause orders under Section 206 of the Federal Power Act to all six regional grid operators (PJM, MISO, SPP, CAISO, ISO-NE, and NYISO), directing each to justify or reform tariff rules governing how data centers and other large loads connect to the transmission grid. The orders address co-location with generation resources, cost allocation for network upgrades, and shortened interconnection timelines—with large load customers expected to bear a greater share of upgrade costs rather than spreading them to ratepayers.

The content in this article reflects practice under existing tariff structures and should be read in light of the June 18 orders. See What FERC’s June 18 Orders Mean for Utility Rate Design and Interconnection for a full analysis of the regulatory implications.

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AFUDC and the Construction Period

During the construction period for dedicated large load infrastructure, the utility is incurring carrying costs on a plant investment that has not yet entered service and is not yet generating revenue. The Allowance for Funds Used During Construction (AFUDC) mechanism compensates the utility for these carrying costs by capitalizing an imputed return on construction-period investment.

AFUDC rates are typically set by regulatory order and are compounded quarterly during the construction period. For large large load customer projects with multi-year construction timelines, AFUDC can be a significant component of the total capitalized cost of the infrastructure. Utility accountants should ensure that AFUDC is calculated and recorded correctly from the first day of capitalization, because errors in AFUDC accumulate over the construction period and can be difficult to correct after the fact.

The AFUDC calculation also interacts with the treatment of CIAC. If a large load customer pays CIAC during the construction period, the utility’s net construction-period investment (and therefore the AFUDC base) is reduced by the CIAC received.

The Interaction with Rate Cases

Data center infrastructure investments that are included in rate base will eventually be reflected in the utility’s revenue requirement in a rate case proceeding. Utility accountants should be prepared to demonstrate:

• That the infrastructure investment was prudent and necessary to serve the large load
• That the costs incurred are reasonable and consistent with the authorized scope of the project
• That dedicated infrastructure costs are properly separated from general system infrastructure costs
• That the CIAC received is correctly reflected as a reduction to rate base

Regulators in rate case proceedings have broad authority to disallow plant investments they find imprudent or excessive. The documentation burden for large, dedicated large load infrastructure investments is correspondingly high. Utilities should maintain comprehensive project records that can support the rate base treatment of these investments through the inevitable regulatory scrutiny that follows large capital additions.