VA Regulators Approve Costly and Unsubstantiated “Direct Transfer Trip” Requirement for Community-Scale Solar
March 5, 2026 (Richmond, Virginia) — Virginia regulators recently issued a major decision that makes permanent increased solar project costs that will slow down clean energy growth in the state. On February 5th, 2026, the Virginia State Corporation Commission filed a decision that allows Dominion Energy to continue requiring an unnecessary and expensive grid protection system called Direct Transfer Trip (DTT) for projects above 250 kilowatts (such as community solar projects and installations on schools, churches, and municipal buildings). Requiring DTT—which has an average cost of at least $300,000—often makes these projects financially infeasible.
Dominion Energy has argued that DTT is necessary to ensure grid reliability but has failed to provide evidence to justify the need for the requirement, or demonstrate its benefit to the electric grid or Dominion Energy ratepayers. Most other states and utilities do not require widespread use of DTT because there are several less costly solutions that are equally effective.
“This is an incredibly disappointing outcome after years of industry-utility collaboration, decades of research, and gigawatts of interconnections in other territories all proving that DTT is arbitrary for use in inverter DER applications,” said Brian Lydic, Chief Regulatory Engineer for the nonprofit Interstate Renewable Energy Council (IREC).
Dominion’s requirement of DTT—commonly referred to as “dark fiber” because it typically involves installing fiber optic lines—is triggered when any project above 250 kW fails an engineering review screen (called the “Load-to-Generation Ratio test”) during the interconnection process. This screen compares the amount of electricity used on a local power line to the amount of electricity that connected solar projects would produce. If the total electricity generated from connected solar projects supplies more than a third of the electricity consumed by nearby customers, every additional solar project above 250kW would then be required to install DTT. This simple test is merely a rule of thumb and is not based on any power systems engineering analysis, yet failure can result in hundreds of thousands of dollars in additional cost. As such, many community, school, and commercial solar projects have been and will continue to be unable to move forward due to cost constraints.
Over the past three years, IREC has engaged in Virginia’s DTT regulatory proceeding to inform the Commission’s decision on this topic. Working alongside Commission Staff, solar industry members, and utility engineers, IREC recommended that the Commission direct Dominion to modify its requirements to match best practices currently in use in other states.
A research paper published by IREC last year demonstrated that DTT is unnecessary for distributed clean energy projects. One of the key findings of the paper is that the probability of grid issues that DTT is designed to prevent is practically zero, occurring only once every 10,000 years. Such issues are so rare, in fact, that only three instances have ever been recorded globally, none resulting in any damage or harm to personnel or equipment.
In its decision, the Commission cited as evidence of the requirement’s reasonableness the fact that 20MW of clean energy development has moved forward after paying for DTT. Yet, over the same timeframe, National Grid in New York installed similarly sized projects at a rate six times faster than Dominion. Without changes to this practice, Virginia will continue to fall behind regions with more modern, evidence-based interconnection requirements.
As part of its decision, the Commission assigned Dominion two follow-up tasks. First, Dominion must propose one additional screen to supplement the simple load test. Second, Dominion must provide additional evidence for why it is imposing the DTT requirement specifically for projects above 250kW. In the process set forth by the Commission, neither of these deliverables is to be reviewed by or co-developed with external parties. This is a significant misstep that prevents input from research institutions and third-party experts that are most informed on interconnection screening practices nationwide.
At the end of the day, Virginia residents will bear the burden of this decision. “It is disappointing that—during a time of historic increases in energy prices, in the data center capital of the world—Virginians will have less access to the energy cost savings of community DERs,” said Shay Banton, IREC Regulatory Program Engineer and Energy Justice Lead.
