What it is
UL 3700 is UL Solutions’ “Outline of Investigation for Interactive Plug-In Photovoltaic Equipment and Systems”. It was published in December 2025, and UL launched its certification program in January 2026. It sets construction, performance and labeling rules written for equipment that plugs into a home outlet, including grid safety and rapid shutdown: the inverter has to stop sending power quickly when the grid goes down.
What's certified so far
- Hoymiles HiFlow Pro, a 360 W, 120 V microinverter, was the first product certified, in July 2026 (CSA Group did the testing). It’s the inverter in Bright Saver’s kit.
- APsystems EZ1 plug-in microinverter, also CSA-certified to UL 3700.
As of July 2026, no complete kit sold in one box had been certified as a whole system, and we couldn’t confirm one as of our Nov 4 check. That matters most in California, where SB 868 requires the whole system to be certified.
What each state asks for
- Names UL 3700 (or equivalent): Maine, Vermont and New Jersey.
- Whole-system certification: California.
- Listed by UL or another nationally recognized lab: Utah, Maryland, Colorado, Connecticut, Virginia and New Hampshire, with Connecticut pointing to UL 1741, the inverter standard.
Every law also requires the inverter to stop sending power when the grid goes down. Each state’s exact rule.
How to check a product
Look for the certification mark on the product label and the listing in the certifying lab’s public directory (UL Product iQ, or CSA’s certified product listing). A seller’s claim of “UL compliant” or “meets UL standards” isn’t a certification. Ask which lab certified it, under which standard, and for the file number.