Grid Storage Dominion Energy Virginia has opened the door to one of the more concrete long-duration storage tests now forming in the United States. The utility is seeking information from companies with technologies that can discharge for at least 10 hours at full nameplate capacity, with a pilot program expected to total at least 4,000 MWh . That number matters. Four gigawatt-hours is not a lab-scale demonstration. It is large enough to force hard questions about siting, interconnection, supply chains, customer cost, and operational control. It also arrives as Virginia faces two overlapping pressures: rapid electricity demand growth and a statutory push to bring much more storage onto the grid. AI-generated image Dominion is looking beyond standard four-hour batteries toward storage that can carry the grid deeper into evening peaks and multi-hour reliability events. What Dominion Is Asking For The request for information asks storage companies to describe their technology, business model, deployment history, timeline to commercial readiness, scalability, siting needs, infrastructure requirements, and material sourcing. Responses are due on Aug. 7, after a six-week window that begins June 26. Dominion has said the pilot could include at least three different technologies. That detail points to a comparative test rather than a single-vendor procurement. In practical terms, the utility appears to be asking which long-duration options are mature enough to be evaluated at grid scale, not which chemistry has the best slide deck. The Core RFI Facts Minimum pilot size: at least 4,000 MWh. Duration definition: 10 hours or more at full nameplate output under Virginia law. Technology mix: at least three technologies could be selected. Deadline: companies have until Aug. 7, 2026, to respond. The RFI does not commit Dominion to procure, invest in, or partner with any respondent. That caveat is normal, but it also keeps the process flexible. Utilities are still sorting out how to compare iron-air, flow batteries, thermal storage, compressed gas systems, advanced sodium chemistries, and other non-standard approaches on a common basis. Why Virginia Is a Useful Test Bed Virginia is not an abstract storage market. It has one of the most visible power-demand growth stories in the country, led by data centers in Northern Virginia and broader electrification across the state. At the same time, the Virginia Clean Economy Act requires the state’s investor-owned utilities to move toward a cleaner generation mix while maintaining reliability. Short-duration lithium-ion batteries already help with fast response, solar shifting, and evening peaks. The hard problem is what happens when reliability needs extend beyond four hours. A hot summer evening, a winter cold snap, a transmission constraint, or a renewable shortfall can stretch well past the duration window of the standard battery projects being built across the U.S. grid. AI-generated image Long-duration storage has to prove it can act like dependable capacity, not just shifted energy. Dominion’s existing battery portfolio has been built in steps. The company has operated smaller pilot projects, including the 12 MW Scott Solar battery and other county-level installations, and has received approval for additional utility-scale storage in Virginia. A 4 GWh long-duration pilot would move the question from basic integration to system planning. The timing also lines up with state policy. Virginia’s storage requirements include large targets for both shorter-duration and long-duration resources over the coming decades. A utility cannot wait until the late 2030s to learn which assets can be permitted, financed, interconnected, and dispatched. The first credible data has to come earlier. The Technology Field Is Wide Open Dominion did not name preferred chemistries in the public RFI summary. That leaves room for several technology families. Iron-air systems can offer multi-day storage but require large footprints. Flow batteries can separate power from energy capacity by expanding tanks, though project economics depend heavily on electrolyte and balance-of-plant costs. Thermal storage can be compelling for industrial heat and power applications, but dispatch characteristics vary by design. Sodium-based systems promise lower material risk, yet commercial scale is still developing. Lithium-ion will not disappear from this discussion. Some lithium systems can be configured for longer durations, and lithium supply chains are far more mature than most alternatives. The issue is cost effectiveness. Once a project moves from four hours to 10 hours or more, adding more lithium cells can become a blunt and expensive way to buy extra energy. 4 GWh Expected minimum pilot size 10+ hr Virginia LDES threshold 3+ Possible technologies Aug. 7 RFI response deadline For developers, Dominion’s process is a chance to show more than headline duration. The RFI asks about deployments to date and commercial timelines, which means vendors will need to explain whether their technology is already operating, nearing first-of-a-kind deployment, or still moving from pilot to manufacturing. That distinction matters for a regulated utility that has to defend costs and reliability assumptions. Procurement Is Becoming the Real LDES Filter The long-duration storage market has spent years arguing over chemistry. The next phase is more practical. Utilities need answers about warranty structure, degradation, forced outage rates, safety codes, cybersecurity, black-start capability, market participation, and whether replacement parts will exist 15 years from now. A 4 GWh pilot can expose those issues quickly. It can also reveal whether a technology is easy to site in the places where storage is most valuable. Some long-duration systems need more land, more water, specialized tanks, unusual permitting pathways, or different fire and environmental reviews than containerized lithium-ion projects. In a state where load growth is concentrated near constrained grid areas, land use can become as important as round-trip efficiency. AI-generated image The next storage race is about bankable projects, not only battery chemistry. Dominion’s RFI also asks about supply chain and material sourcing. That is a critical point for any U.S. utility. Battery buyers have been dealing with tariff exposure, China-linked supply-chain scrutiny, domestic-content rules, and shifting tax-credit eligibility. Technologies that reduce dependence on lithium, cobalt, nickel, or imported cells may find a receptive audience, but only if they can scale without creating a different bottleneck. A Signal for the Wider U.S. Storage Market The U.S. storage market is still dominated by lithium-ion systems built for two to four hours of discharge. That segment is growing fast because it solves immediate grid needs and benefits from a deep supplier base. Long-duration projects, by contrast, remain scattered across pilots, grant-backed demonstrations, and a few large utility commitments. Dominion’s RFI does not change that market overnight. It does show that utilities are beginning to formalize the next question. If four-hour storage becomes a standard grid asset, what fills the gap between conventional batteries and new firm generation? In markets with high renewable penetration and fast load growth, that gap can become expensive. The answer may not be one technology. Virginia’s pilot structure appears designed to compare multiple options under the same utility planning lens. That is useful because different long-duration assets may serve different jobs. A 10-hour system that cycles frequently is not the same product as a 100-hour system designed for rare reliability events. A compact battery near load is not the same as a large, low-cost system sited far from congestion. The bottom line: Dominion’s 4 GWh RFI is a market test for long-duration storage vendors and a planning test for Virginia. The winning techn