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Two standards and a certification lab unbundle AC vehicle-to-grid from the certified vehicle-charger pair

Pair certification is the reason vehicle-to-grid has stayed a decade of vendor demonstrations rather than a market. If a car can discharge only into the charger it was tested against, the carmaker rather than the owner decides what hangs on the wall, and an aggregator signing up that car inherits whatever the manufacturer picked. Decoupling the two certifications turns a parked EV into an interchangeable grid asset, moves the hardware decision to the person paying for it, and lets an aggregator address a fleet defined by a standard instead of by a partnership. The AC route matters because it is cheap, since the inverter is already in the car, though that cost claim comes from the certifying body and the vendors, not from an independent finding, and the Vehicle-Grid Integration Council which supplied the timeline is a trade association whose members lobbied for these standards. The correction worth carrying is on the clock: a standard, a certification lab and an interconnection rule are three separate gates, and only the first two are through.

Two standards and a test lab have unbundled vehicle-to-grid from the certified vehicle-charger pair

UL 1741 Supplement SC and ISO 15118-20 Amendment 1 were published eight weeks apart. On 14 September UL Solutions opened the lab that turns them into products.

For a decade, AC vehicle-to-grid has been gated by a certification rule rather than by physics: a vehicle and a charger had to be tested and approved together, as one system. Two standards published this year removed that requirement, and a certification programme opened this month makes the removal operational.

UL Standards & Engagement published UL 1741 Supplement SC on 21 May 2026, covering AC bidirectional electric vehicle supply equipment for vehicles with onboard inverters built to SAE J3072. The mechanism is the important part. The supplement, in the Vehicle-Grid Integration Council's summary, "supports the interconnection of a charger as an 'oversight supervisor'" for any vehicle designed and tested to J3072. The charger takes responsibility for the grid connection; the vehicle's onboard inverter is certified separately, once, against a vehicle standard. Neither has to know about the other in advance.

ISO 15118-20 Amendment 1 followed on 13 July 2026, adding bidirectional power transfer, AC distributed-energy-resource services, Megawatt Charging System services and a revised security model to the vehicle-to-charger communication protocol. UL 1741 SC settles what the equipment is permitted to do; ISO 15118-20 settles how the two ends negotiate it. [UNVERIFIED: the ISO publication date and scope. ISO's own catalogue page for the standard returned HTTP 403 on 22 September 2026 and again on both attempts, so these details rest on secondary sources.]

On 14 September 2026, four months after the supplement was issued, UL Solutions opened a certification programme for this equipment, testing to UL 1741 SC, UL 9741 and SAE J3072 at laboratories in Fremont, California and Northbrook, Illinois. Wesley Kwok, vice president and general manager of the company's Energy and Industrial Automation group, said electric vehicles "spend much of their time parked", which he framed as an opportunity for them to do more than transport people.

Why pair certification mattered

Pair certification is the reason V2G has stayed a collection of vendor demonstrations. If your car can discharge only into the specific charger it was tested against, then the carmaker, not the owner, decides what hardware sits on the wall, and an aggregator signing up that car inherits whatever the manufacturer chose. Every V2G pilot of the last decade has been a bilateral deal in this shape, which is why they have been announced more often than they have been scaled.

Decoupling the certifications turns a parked EV into an interchangeable grid asset and moves the hardware decision to the person paying for it. It also changes who can build a business on it: an aggregator can address a fleet defined by a standard rather than by a partnership, and a charger manufacturer can sell into every J3072 vehicle rather than negotiating model by model. That is the difference between a demonstration and a market.

Two cautions. The AC route matters largely because it is cheap: the inverter is already in the car, so the wall unit does not need one, and UL Solutions says this should make the equipment substantially less expensive than DC bidirectional hardware. That is the vendor's claim about its own newly certifiable category, not an independent finding. And the Vehicle-Grid Integration Council, which supplied the timeline above, is an industry trade association whose members have been lobbying for exactly these standards. Neither point makes the dates wrong. Both are worth holding while reading them.

The regulatory clock, corrected

California's interconnection rules are the near-term test, and the timeline is slower than it first appears. On 10 July 2026, the state's three large investor-owned utilities formally notified the California Public Utilities Commission that UL 1741 SC had been published. That notification started a clock: CPUC staff were authorised to reconvene a dormant V2G AC interconnection working group by 19 August 2026. The utilities then have eight months from the reconvening to propose updates to Rule 21 accommodating V2G AC, or, if the industry standards are found insufficient, to keep offering an interim pathway.

So 19 August 2026 was the deadline to restart the conversation, not the deadline to produce rules. On that schedule, proposed Rule 21 language lands around April 2027, and adopted language later still. A standard, a certification lab and an interconnection rule are three separate gates, and only the first two are through.

What is still unknown

How many vehicles on sale today ship with SAE J3072 compliance, and which models. Whether the CPUC working group actually reconvened by 19 August 2026, and what the utilities have filed since. How long from certification opening to the first UL 1741 SC certified charger reaching the market, and at what price. Whether India's charging standards work references ISO 15118-20 at all or continues on its own path, which would determine whether any of this arrives there. [NEEDS DATA: count of J3072 compliant vehicle models on sale] [NEEDS DATA: number of chargers certified to UL 1741 SC to date] [NEEDS DATA: the CPUC proceeding number for the V2G AC working group]

Sources

slug: ac-v2g-ul1741-sc-iso15118-20-amd1 beat: 3 format: news_brief meta_description: UL 1741 SC and ISO 15118-20 Amendment 1 end pair certification for AC vehicle-to-grid, and UL Solutions opened the certification lab on 14 September 2026. tags: [V2G, bidirectional charging, UL 1741, ISO 15118-20, SAE J3072, Rule 21] internal_links: [] review_flags: needs_data: - Count of SAE J3072 compliant vehicle models on sale - Number of chargers certified to UL 1741 SC to date - The CPUC proceeding number for the V2G AC interconnection working group unverified: - ISO 15118-20 Amendment 1 publication date and scope; the ISO catalogue page returned HTTP 403 - Whether the CPUC working group reconvened by 19 August 2026 - The claim that the EU will mandate ISO 15118-20 on public charge points from 1 January 2027, which is secondary-source only and is not used in this piece legal_sensitive: false confidence: medium

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