Is Duke Energy Missing Out on 400 MW of Storage?

North Carolina faces a pivotal decision that will shape its energy costs for the next decade. Duke Energy wants to build new natural gas plants, but clean energy advocates argue that's the wrong answer — and they have the utility's own modeling software to prove it.

Vote Solar and the Southern Environmental Law Center recently filed expert testimony with the North Carolina Utilities Commission challenging Duke's Carbon Plan and Integrated Resource Plan. The core argument isn't ideological; it's mathematical. Duke's planning process excluded 400 megawatts of behind-the-meter battery storage from its analysis — and when that storage is included, the model itself selects it as a top cost-saving measure.

That's not a minor oversight. That's 400 MW of customer-owned capacity that never made it into Duke's resource calculus.

What Duke's Plan Actually Says

Duke Energy's current roadmap commits significant capital to methane gas infrastructure and continued operation of coal units. The utility's stated rationale is straightforward: rising industrial load demands grid reliability, and fossil fuels deliver it. Given the pace of data center growth and industrial reshoring across the Southeast, that load growth concern isn't imaginary.

However, the argument that fossil fuels are necessary for reliability only holds if the alternatives were properly evaluated. According to Vote Solar's testimony, they weren't.

The 400 MW in question consists of behind-the-meter battery systems — storage installed at commercial, industrial, and residential customer sites rather than at utility-owned substations. These aren't hypothetical resources waiting to be built; they represent existing and near-term deployable capacity that Duke's modeling software simply didn't account for.

The Case for Distributed Energy Resources

Behind-the-meter storage operates differently from a utility-scale plant, and that difference is actually the point. Customer-sited batteries can be aggregated into virtual power plants — coordinated fleets of distributed assets that respond to grid signals as if they were a single generator. During peak demand events, when the grid is most stressed and peaking plants run at their highest cost, a virtual power plant can dispatch stored energy directly where it's needed, without transmission losses.

Vote Solar's testimony found that solar paired with storage can reduce peak demand by more than 80% — a figure that should make any resource planner pause before signing off on a new gas peaker.

The economics work in multiple directions. Distributed storage reduces the need for expensive transmission upgrades since power is generated and consumed closer to load. It eliminates the fuel price exposure that comes with gas-fired generation. And because these are customer-owned assets, they represent capacity Duke doesn't have to build, finance, or maintain.

That last point deserves emphasis. When a utility builds a new gas plant, ratepayers carry the capital cost plus the ongoing fuel cost plus the financing. When a customer installs a battery, that capital sits off Duke's books entirely — while the grid benefits remain accessible through aggregation agreements.

The $8 Billion Number, Put in Context

Jake Duncan, Vote Solar's Southeast senior regulatory director, argues that an alternative portfolio centered on solar, wind, and storage could save North Carolina customers up to $8 billion through 2035. That's a headline figure, and it warrants scrutiny — but the underlying logic is sound.

Gas plant economics have two embedded risks that storage doesn't carry: fuel price volatility and stranded asset risk. A gas plant built today will still be on the books in 2040, generating rate base returns and requiring fuel purchases at whatever natural gas happens to cost then. Solar and storage have higher upfront costs but near-zero operating costs once installed. Over a long planning horizon, that profile tends to win.

The $8 billion estimate represents the cumulative spread between fossil-heavy and clean energy portfolios — and it's the kind of number that regulators, not just advocates, need to consider.

For context, North Carolina has roughly 4.8 million electric customers through Duke's service territory. Eight billion dollars over nine years works out to meaningful savings per household — the kind of savings that shows up in monthly bills, not just in analyst reports.

The Regulatory Moment

The North Carolina Utilities Commission has scheduled an expert witness hearing on the resource plan for July 1, 2026, with a final order expected by year-end. That timeline matters. Whatever the commission decides will lock in North Carolina's energy trajectory for years, influencing where capital flows, which assets get permitted, and what ratepayers pay through the 2030s.

The proceeding is publicly accessible — the commission will stream the hearing on its YouTube channel — which means the arguments playing out in regulatory filings will have an unusual degree of public visibility.

For developers, investors, and landowners active in the Carolinas market, the outcome has direct implications. A commission order that validates distributed storage as a planning resource opens procurement pathways for virtual power plant aggregators. A decision that green-lights Duke's gas buildout doesn't close those doors entirely, but it delays and complicates the business case.

The insider read here: utility resource planning proceedings often turn on whether alternative resources are modeled with the same rigor as the utility's preferred option. Vote Solar's testimony appears specifically designed to establish that Duke's modeling was incomplete — not just wrong — which is a more durable regulatory argument. If the commission agrees that the analysis was flawed, it can require Duke to redo it rather than simply adjudicating between two competing portfolios.

What Comes Next

North Carolina's commission has real authority here, and this proceeding is worth watching closely. The question isn't whether battery storage works — it does, at scale, in dozens of markets. The question is whether a regulated utility's planning process will be required to reflect that reality.

Duke's own modeling tools, by Vote Solar's account, already know the answer. When customer batteries are in the model, the software selects them. The fight in Raleigh this summer is fundamentally about whether the inputs to that model can be curated to produce a predetermined outcome — or whether the commission demands a complete analysis.

For anyone with assets, capital, or customers in North Carolina's energy sector, the July hearing is the event to track. The final order won't just be a decision about Duke's resource plan. It will signal how seriously the state intends to treat distributed energy resources as legitimate infrastructure — and that signal will echo well beyond 2026.

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[INTERNAL LINK: Duke Energy's Carbon Plan]

[INTERNAL LINK: Virtual Power Plants]

[INTERNAL LINK: Distributed Energy Resources]