UL Starts Certifying AC Bidirectional EV Chargers to UL 1741 SC
- EVs Infrastructure & Grid Connection Regulatory
Marin Holt
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- 8 minutes read
- Standard: UL 1741 Supplement SC
- Vehicle-side requirement: SAE J3072 onboard inverter, finalized 2024
- Test labs: 2 US sites, Fremont CA and Northbrook IL
- Per-vehicle value of two-way flow: 5 to 15 times one-way managed charging
Builders of vehicle-to-grid hardware now have a compliance path that did not exist a week ago. UL Solutions opened testing and certification on September 14, 2026 for bidirectional electric vehicle supply equipment, known as BEVSE, under UL 1741 Supplement SC. The work runs at two United States labs, one in Fremont, California and one in Northbrook, Illinois. Solar Power World, citing an E3 study commissioned by General Motors, puts the per-vehicle value of two-way power flow at five to 15 times the value of one-way managed charging.
The certified box sits between a building’s AC wiring and a parked car. It does not convert the power itself. That job moves onto the vehicle, which must carry an onboard inverter tested to SAE J3072.
What Actually Changed
Until now, a manufacturer wanting a listed two-way charger in the United States had one practical route. That route was UL 9741, the standard for electric vehicle power export equipment, which covers DC equipment holding its own inverter. Suppliers including dcbel, Sigenergy and Wallbox build to that DC model.
UL 1741 Supplement SC opens a second route. The wallbox stays a switching and control device. The inverter lives in the car. UL Solutions describes the supplement as recently published, and it rests on SAE J3072, which the auto industry finalized in 2024. ESS News reports that the AC path took more than a decade of coordinated work across the standards bodies.
What Did Not Change
UL 9741 stays in force. DC equipment already certified to it keeps its listing, and the new supplement does not retire that path. Nothing in the announcement changes an interconnection agreement. A utility still decides whether a given vehicle exports to its grid, and on what terms.
The vehicle side also stays where it was. An AC wallbox certified to Supplement SC does nothing for a car without a J3072 inverter. Very few models sold in the United States carry one today.
Why It Matters
Moving the inverter into the car takes cost out of the wall. A building-side device that only switches and controls costs less to build than one carrying power electronics. That matters most for fleet depots and schools, where the count of charge points drives the bill.
Wesley Kwok, vice president and general manager of the energy and industrial automation group at UL Solutions, framed the opportunity around idle time. “Electric vehicles spend much of their time parked, creating an opportunity for them to perform more than transportation alone,” he said. Solar Power World reports that about 90% of electric vehicles sit parked at any given moment.
The gap now sits with the automakers. Certification labs are open and the standard is published. Until cars ship with J3072 inverters in volume, an AC-certified wallbox has nothing to talk to.
Enforcement Reality
No federal rule orders anyone to certify to Supplement SC. Enforcement arrives through the electrical inspector and the interconnecting utility, not through UL Solutions. An authority having jurisdiction asks for a listing before it signs off on a permit. A utility asks for proof that the equipment meets its interconnection requirements before it allows export.
That makes the practical test a commercial one. A manufacturer without the listing faces inspectors and utilities who have a documented reason to say no. A manufacturer with it clears both desks faster.
Critical Perspective
The labs are open before the cars arrive. A wallbox certified to UL 1741 Supplement SC needs a vehicle whose onboard inverter meets SAE J3072, and that standard was only finalized in 2024. UL Solutions did not say how many vehicle models sold in the United States carry a J3072 inverter today. Without that count, the certification reads as readiness rather than as capacity.
The five to 15 times figure also deserves its provenance. Solar Power World attributes it to an E3 study commissioned by General Motors, an automaker with a direct commercial interest in two-way charging. That does not make the number wrong. It does mean the most quoted value claim in this announcement did not come from a neutral party, and UL Solutions published no cost figure of its own for what a Supplement SC listing takes.
Certification also stops at the equipment. UL Solutions does not sign interconnection agreements. A homeowner with a listed wallbox and a compliant car still needs the utility to permit export, and the two paths now in force, UL 9741 for DC and Supplement SC for AC, give inspectors two different documents to learn. Whether that speeds deployment or splits it is the open question.
