What UL 3700 is, and why almost nothing is certified yet

Why a new standard was needed

Plug-in solar is a genuinely new category, and the existing standards didn't cover the thing that makes it different.

UL 1741 covers grid-interactive inverters. It's a serious standard and it's been around for decades. What it assumes is a professionally installed system, hard-wired, connected on a dedicated circuit, inspected.

A plug-in device breaks all four assumptions. It's installed by a member of the public, it connects through a receptacle, it shares a circuit with a toaster, and nobody inspects it.

That creates questions UL 1741 doesn't ask. What happens when a device injects current downstream of a breaker on a shared branch circuit? How does it interact with residual-current protection in a GFCI outlet? What happens if someone plugs two of them in? What if the cord gets unplugged mid-production and someone touches the pins?

UL 3700 asks those questions.

What it actually covers

Broadly: the electrical safety of the complete plug-in photovoltaic device, tested as the thing a consumer would actually plug in. That includes the interaction with branch-circuit protection, behaviour with ground-fault devices, safe de-energisation when unplugged, anti-islanding, and the mechanical and environmental durability of a device that lives outside.

The details matter to manufacturers rather than to you. What matters to you is that the standard exists and that a laboratory has tested against it.

Where things stand

The Assembly's Utilities and Energy Committee analysis in June 2026 found that no commercially available balcony solar system had achieved the certification, and observed that the requirement would effectively hold adoption back until manufacturers responded.

Since then:

• Hoymiles announced the HiFlow Pro on 15 July 2026, described as the first UL 3700 compliant plug-in microinverter in the US, at 360 watts a unit.
• APsystems cleared the standard with the EZ1-LV through CSA.
• No complete kit — panel, inverter, mounting and cabling certified as an assembly — has done it, as far as we can establish. This is the fact on this site most likely to change first, and we re-check it before every kit-page update.

Why so slow

Certification costs money and takes months, and manufacturers were waiting to see whether California would pass anything before spending it. Utah's market alone, at 1.1 million households, doesn't obviously justify the expense. California's 13.55 million does.

If the Governor signs, expect a wave. If he vetoes, expect the wave to go to New York and New Jersey instead.

What to look for when you're buying

Good: "Certified to UL 3700," with a named laboratory — UL, CSA or Intertek. Ask for the certificate; a legitimate manufacturer will send it.

Acceptable, for now: a microinverter certified to UL 3700 in a kit whose other components carry their own listings. This is the best available answer today and it's what we'd buy.

Weaker: UL 1741 or ETL to UL 1741. A real listing, not the plug-in standard. Fine before January 2027; possibly not sufficient after.

Suspicious: "UL certified components," "meets all applicable safety standards," "CE marked." The first is vague by design, the second is meaningless, and the third is a European self-declaration that carries no weight in the US.

Run a product through our checker → · What's certified today →

The 2030 deadline nobody's talking about

One more thing in SB 868 worth knowing: from 1 January 2030, it becomes illegal to sell a receptacle-connected plug-in photovoltaic device in California that doesn't meet the definition — which means the certification requirement.

That's a permanent provision, unlike the interconnection exemption, which sunsets on the same date. So the market has three and a bit years to get certified, and after that the uncertified products simply can't be sold here.

For you, buying now: it doesn't make an uncertified device illegal to own. It does mean an uncertified device is a product with no future, which matters for support, firmware and warranty service.