In May 2024, Duke Energy said it was working with Amazon, Google, Microsoft, and steel company Nucor to develop a tariff structure for large loads coming online in the Carolinas to support clean energy. That framework, Duke explained at the time, would include a clean transition tariff, a rate structure originally developed by Google and Nevada Energy that allows large customers to fund novel clean energy resources without passing the costs of those not-yet-commercialized technologies on to other ratepayers.
That original announcement was made with much fanfare at a White House summit. But over two years later, it still hasn’t led to a formal tariff proposal. The next time Duke itself mentioned a CTT in an official proceeding was February 2026, when the idea resurfaced in a settlement over the proposed merger of Duke’s two Carolina utilities. In that settlement, Duke committed to “engaging with Google to receive and consider in good faith” a detailed proposal for a CTT.
(Google didn’t respond to a request for comment on whether it has since presented such a proposal.)
When Duke set out earlier this summer to develop a tariff to address massive data center growth in the Southeast, a broad swath of stakeholders, including regulators, large loads, environmental groups, and the North Carolina attorney general’s Office, supported the inclusion of a clean transition tariff.
“Duke Energy’s prior efforts to voluntarily establish a CTT have languished,” the attorney general noted.
The Clean Energy Buyers Association, meanwhile, went so far as to ask the commission to direct the utility to file a CTT within six months, citing the Trump administration’s ratepayer protection pledge: “A clean customer tariff provides a practical mechanism for customers to meet that commitment,” the association said.
Duke filed the final version of its large load tariff proposal this week. It requires large loads to cover the total cost of any new infrastructure dedicated to the project, to provide letters of credit to cover needed transmission upgrades, and to sign 10–15 year contracts, among other things. It has the support of large load customers including Amazon, Google, and Microsoft. It does not, however, include a clean transition tariff.
“No party has presented even remotely sufficient detail to support a CTT program at this time,” Duke told the commission. Proponents of a CTT need to provide “extensive detail” on things like program design, pricing, and credits, so that the utility can “ensure the program does not harm non-participating customers,” the filing added.
However, according to testimony from commission staff, large load customers “tried to work with [Duke] and the Public Staff to implement a new clean transition tariff.”
Deprioritizing a CTT
At this point, the 2024 memorandum of understanding that Duke and the hyperscalers is essentially dead. Nick Jimenez, a senior attorney at the Southern Environmental Law Center, which represents environmental and clean energy advocates in proceedings before the North Carolina Utilities Commission, said nobody involved considers it currently active.
After that initial announcement, there were around 18 months of back and forth, but the parties “just never got to where they needed to get to file something.” (None of the parties to the announcement responded to Latitude Media’s request for comment.)
That initial delay was disappointing, but last October, when the commission held a technical conference on large load tariffs, things started to look up. “It was telegraphed coming out of that proceeding that the rate cases were going to be the place to handle [a CTT],” Jimenez explained.
The possibility of a CTT came up again in a public stakeholder meeting earlier this year, and while “nobody was opposed, there were more things to figure out,” he said. The feeling in the room was that creating a large load tariff would be hard enough, and that developing a CTT in parallel would be overly complicated, Jimenez recalled. That’s not necessarily the position of SELC or of the large load customers, he clarified, but it was “the center of gravity in those discussions.”
In its filings this week, things became more official. Duke urged the commission to “decline to include any [CTT] provisions” in the rate case proceeding in part because the utility’s existing green tariff program “should be fully explored with respect to meeting large load customer needs before additional programs are determined to be necessary.”
That program allows large electricity users to procure renewable energy and its associated environmental attributes through Duke, including by paying to accelerate some solar and storage projects. When regulators approved it in July 2024, shortly after the CTT announcement, critics argued the program would largely be used to subsidize renewable projects Duke was already likely to build, thanks to North Carolina’s 2050 carbon neutrality mandate, rather than drive additional development.
A clean transition tariff is intended to instead encourage the development of new carbon-free resources, like enhanced geothermal or long-duration energy storage, that wouldn’t be economical for the utility at such an early technological stage. To date, Nevada remains the only place where the framework has been formally adopted.
Duke isn’t alone in considering a CTT, including as part of a large load tariff. In Colorado, Xcel Energy subsidiary Public Service Company has proposed an optional CTT alongside its broader framework for interconnecting large loads. Meanwhile, Minnesota’s public utility commission directed Xcel to develop a clean energy and capacity tariff as part of its own large load proceeding. Xcel has already announced a custom, CTT-like arrangement with Google that involves developing a long-duration energy storage project to help power a new data center.
