We earn commissions from qualifying purchases through links on this page (Amazon Associates, eBay Partner Network, and select brand programs). It doesn't change what we recommend. Prices move constantly, so we use $ / $$ / $$$ tiers instead of quoting numbers.
The short version
- UL 3700 is the first US safety framework written specifically for solar that plugs into a wall outlet.
- It was published at the end of 2025, and UL Solutions opened certification in January 2026.
- Its signature requirement: the plug must go dead within about one second when you unplug it.
- It builds on UL 1741 SB (inverter grid behavior) rather than replacing it.
- Certified products are still scarce, so learn to verify listings yourself.
For years, the reason US retailers wouldn't sell balcony solar kits wasn't that anyone had proved them dangerous. It was that no US safety document described them. Rooftop solar has a mature stack of standards: UL 1741 for inverters, UL 61730 for panels, and Article 690 of the National Electrical Code for installation. All of it assumes a professionally installed, hardwired system. A product whose whole purpose is to be plugged into a household outlet by a non-electrician fell between every existing document.
UL 3700 is the attempt to close that gap, and it's now referenced directly or indirectly by most new state plug-in laws. Here's what it is, what it requires, and how to tell whether the product in your cart actually meets it.
What UL 3700 is (and isn't)
UL 3700's full title is the Outline of Investigation for plug-in photovoltaic equipment and systems. An Outline of Investigation is a certification framework that labs can test against right away, before it has gone through the full consensus process to become an ANSI-approved standard. That's why it could be used for certifications within weeks of publication, and why you may see it described as either an "outline" or a "standard."
It covers the plug-in system as a whole: panels, microinverter, cord, plug and how they behave together when a consumer connects them to a branch circuit. It can certify a single microinverter intended for plug-in use or a complete kit tested as one unit.
What it isn't: a replacement for UL 1741. Grid-interactive inverters still need the anti-islanding and grid-support behavior that UL 1741 SB (aligned with IEEE 1547) verifies. UL 3700 adds the plug-in-specific protections on top.
The core requirements
Regulators cite the same risks in almost every plug-in hearing, and UL 3700 is organized around them:
1. Shock from a live plug. With a normal appliance, current flows from the wall into the device, so an unplugged cord is dead. A solar microinverter produces power, so an unplugged cord on the solar side could, in principle, have live prongs in bright sun. UL 3700 requires the plug to de-energize within about one second of disconnection. Some microinverters do this in hardware by watching for the reference signal from the outlet and shutting down the moment it disappears.
2. Islanding and backfeeding during outages. When the grid goes down, a grid-tied inverter must stop exporting so it can't energize lines that crews are working on. That's UL 1741 SB territory, and UL 3700 builds on it.
3. Branch-circuit overload. Current from a plug-in system enters the circuit at the outlet, which means a load on the same circuit can draw from both the breaker and the solar at once. The breaker only sees the grid portion. UL 3700 addresses overload protection and pushes manufacturers toward safe installation limits, which is one reason state laws cap output around 1,200 watts.
4. Accidental contact with hazardous parts during installation and handling.
5. Safe installation guidance written for consumers rather than licensed installers.
Some explainers also report that the framework favors dedicated, non-standard connectors to prevent plugging into unsuitable circuits. Product approaches differ, and many kits sold today use ordinary outlets, so read the certification scope and the manufacturer's instructions for the specific product.
UL 3700 vs UL 1741 at a glance
| UL 1741 (SB) | UL 3700 | |
|---|---|---|
| Written for | Grid-interactive inverters, typically hardwired | Solar that plugs into an outlet |
| Anti-islanding | Yes | Builds on UL 1741 SB |
| Dead plug on unplug | Not addressed | Required |
| Branch-circuit considerations | Not plug-in specific | Addressed |
| Consumer install guidance | Installer-oriented | Consumer-oriented |
| Named in state laws | Often implied by "UL listed" | Named in newer laws such as Maine; Colorado above 391 W |
How state laws use it
State laws handle certification in three ways. Early laws like Utah's say "UL or equivalent" without naming a standard, because UL 3700 didn't exist yet. Maine's LD 1730 was the first enacted law to name UL 3700 while allowing comparable standards. Colorado requires UL 3700 for systems above 391 watts, and Maryland exempts devices of 391 watts or less from certification. Our state-by-state law guide has the details for every enacted state.
What's actually certified right now
Honestly, not much. The certification program opened in January 2026 and product testing takes months. APsystems says its EZ1-LV microinverter is certified to UL 3700, and several kit makers say they're in the pipeline. At least one Colorado cooperative told members in summer 2026 that no consumer product yet met the requirement for the state's upper tier. We track what's available in our UL 3700 kit guide.
How to verify a listing in five minutes
- Get the full model number, including any suffix.
- Look at the certification mark (UL, CSA, ETL/Intertek, TÜV) to see which lab issued it.
- Search that lab's public certification directory for the model.
- Read the listing: it should name UL 3700 (or UL 1741) and the specific model.
- Check the scope. A microinverter listing doesn't automatically cover a third-party kit's cable and panels.
"UL compliant," "built to UL standards," "UL pending" and "tested to UL" don't mean the product is listed. Only a listing in the certifier's directory counts.
Should you buy a non-UL 3700 system today?
It depends on where you live and how big a system you want. In a state that accepts general UL or NRTL listing, a documented UL 1741 SB microinverter is the mainstream choice. In Colorado or Maryland, systems at 391 watts or less don't need certification at all, though we'd still buy listed hardware. In a state or tier that names UL 3700, wait for a verifiable certification rather than hoping your utility doesn't ask.
Whatever you buy, keep a dated screenshot of the listing with your records.
UL-listed plug-in microinverter
$$Best for: Builders who want the component regulators check first
The microinverter is the heart of any plug-in system and the part certification is about. Buy by listing, not by brand reputation, and match its AC rating to your state cap.
Strengths
- The key certified component
- Two-panel inputs are common
Trade-offs
- UL 3700 units are still limited
- Confirm the exact model on the certifier's site
For storage and off-grid systems we also track Bluetti power stations and Renogy panels, charge controllers and batteries direct from the brands.
Frequently asked questions
What is UL 3700?
UL 3700 is the Outline of Investigation for plug-in photovoltaic equipment and systems, the first US safety framework written specifically for solar that plugs into a household outlet.
When was UL 3700 published?
It was published at the end of 2025, and UL Solutions launched its certification program in January 2026.
What's the difference between UL 3700 and UL 1741?
UL 1741 covers grid-interactive inverter behavior such as anti-islanding. UL 3700 builds on it and adds plug-in-specific protections like a plug that de-energizes within about a second of being unplugged.
Is any plug-in solar kit UL 3700 certified?
Very few as of September 2026. APsystems states its EZ1-LV microinverter is certified to UL 3700. Verify any claim in the certifier's public directory.
Do I need UL 3700 to install plug-in solar legally?
It depends on your state and system size. Colorado requires it above 391 W, Maine names it, and other states accept general UL or NRTL listing.