Reference D · Microinverter comparison
What's actually certified, what isn't, and what's still being sorted out.
A microinverter is a small device, roughly the size of a hardcover book, that converts the direct current (DC) a solar panel produces into the alternating current (AC) a home's outlets and appliances actually use. Traditional rooftop systems typically run one large "string inverter" for an entire array of panels; plug-in systems instead pair one microinverter with just one or two panels, doing the same conversion on a much smaller scale.
For plug-in solar specifically, the microinverter is doing almost all of the safety-critical work. It tracks each connected panel's voltage and current to pull the most usable power available, and it includes anti-islanding protection, the feature that automatically shuts the system off the instant it detects a grid outage, so it never keeps a line energized that a utility crew might be working on. It's also the component nearly every certification discussed on this page (UL 1741, UL 3700) actually applies to, not the panel. Picking the right microinverter, and confirming what it's actually certified to do, matters more for anyone setting up a plug-in system than panel choice does.
This page exists because the panel-and-inverter voltage math covered in the main story isn't specific to one piece of hardware. Every plug-in microinverter has an MPPT window, maximum power point tracking, shorthand for the range of voltages the inverter can actually read and use from a connected panel, and it's a structural feature of the whole plug-in microinverter category that these windows run narrow. This is what's actually verifiable right now, pulled from manufacturer datasheets, official certificates, and a few primary-source cross-checks, not buyer-guide summaries. Where something is still unresolved, it's marked as such rather than smoothed over.
Four purpose-built, US-relevant plug-in microinverters with documentation:
| Model | MPPT window | Panel/module range | Max output | US certification |
|---|---|---|---|---|
| APsystems EZ1-LV | 27–45V | 315–660W+ | 900VA | UL 1741 + UL 3700 (confirmed via CSA certificate) |
| Hoymiles HiFlow Pro (HMS-…-1WM-LV) | 16–60V | 280–670W+ per panel | 360–500VA/unit, up to 1,200W stacked | UL 3700 (first purpose-built plug-in unit certified in the US) + UL 1741 |
| EcoFlow STREAM (EF-PS-1200, NA) | 16–60V | 200–600W per port group | 1,200W (scales 360→1200W with breaker/wire gauge) | UL 1741 confirmed; UL 3700 not yet |
| NEP Liberty BDM-1200-LV | 22–55V | up to 600W × 3 | 1,200W | UL 1741 confirmed; UL 3700 claimed on one internal-looking datasheet, unconfirmed everywhere else (see below) |
Two different certifications show up throughout this page. UL 1741 is the baseline safety and grid-interaction standard essentially every grid-tied inverter needs, plug-in or not. UL 3700 is newer, specific to plug-in and balcony solar hardware, and covers the added risk of a system installed by the homeowner rather than an electrician. A CSA certificate is simply the paperwork proving a product passed one of those tests, issued by CSA Group, the organization that runs the testing. The "VA" figures in the table (volt-amps) are effectively equivalent to watts for hardware like this, just measured slightly differently.
It's easy to read "UL 3700 certified" as shorthand for "plug it in anywhere, no restrictions." The actual certificate says something more specific. Pulling the real CSA certificate for the APsystems EZ1-LV (the hardware behind this whole project) turned up conditions that don't show up on marketing pages:
A dedicated 10-amp circuit is required. Not "any household outlet": a specific, dedicated 10A branch circuit.
A bidirectional Class A GFCI is required if the circuit isn't dedicated.
The certification isn't standalone. It covers the inverter as part of a matched system with a specific proprietary locking plug and cord, not as an interchangeable component.
Certification doesn't automatically transfer to the whole installed system. The certificate itself notes that UL 3700's system-level section has to be "revisited" once the inverter is actually integrated into a real installation.
None of that is a red flag on the hardware. It's just a more precise picture than "certified" implies on its own, and it's the kind of detail that only shows up when you go past the marketing copy to the actual certificate.
That last condition above points at something bigger than one product. Every UL 3700 certification found in this research, across every brand, covers the inverter alone (subassembly-level), not the complete installed system of inverter, panels, cables, and mounting hardware together (whole-system level). Bright Saver, a reputable plug-in solar retailer, confirms this directly on their own FAQ page: they don't ship to Maine, New York, or Vermont, because those three states require whole-system certification, and as they put it, "no vendor in the industry has achieved that yet."
This applies to the hardware behind this project too. The EZ1-LV's UL 3700 certification is real and current, and it's still subassembly-level, not whole-system. Not just one brand: the entire category lags behind the certification.
Northern Electric & Power is a Silicon Valley-based manufacturer with a decade in the standard rooftop microinverter market, and their newer Liberty BDM-1200-LV is a purpose-built plug-in unit, independently confirmed on the California Energy Commission's public equipment list. But there's an unresolved discrepancy worth flagging plainly: one internal-looking datasheet (filename ending in "UL-Certs-Completed") claims UL 3700 certification. NEP's own live product page doesn't mention UL 3700 at all, describing the unit as UL 1741 and CEC-listed only. Two independent retailers describe it the same, UL 1741-only, way. The physical dimensions listed on the datasheet and on NEP's own website don't even match each other. An inquiry was sent to NEP directly to clarify; as of August 2026, no response has come back. Until there's a direct certificate to point to, this page treats NEP's UL 3700 status as unconfirmed, not certified.
Craftstrom markets their Hedy microinverter kits as legal in all 50 states, and it's worth being precise about what that claim actually rests on, because it isn't based on UL certification. Craftstrom's own manual and marketing are consistent with each other on certifications (UL 1741, IEEE 1547, NEC, VDE, CE, FCC), and at least one independent reviewer notes plainly that Craftstrom doesn't have UL 3700 yet and expects it later in 2026.
The 50-state claim instead rests on a completely different mechanism: a zero-export architecture, hardware and software working together to guarantee the system never sends any power back out to the grid at all. Craftstrom pairs the Hedy inverter with a "Smart Breaker" that monitors branch-circuit load (how much power the specific circuit it's plugged into is already drawing) and disconnects near 80% of that circuit's rating, and a "PowerMeter" that tracks household load in real time and throttles the inverter's output to prevent any export to the grid at all. The legal argument, as stated by one Craftstrom partner, is that utilities regulate what connects to their grid, but have no jurisdiction over what happens entirely on the customer's side of the meter, on the theory that a system that never backfeeds, sends power the wrong direction back into the grid, isn't really "interconnected" in the way the rules are written to cover.
That's a genuinely different legal theory than the UL 3700-and-state-legislation path every other brand in this comparison is pursuing, and it's contested, not settled. A community discussion on DIY Solar Forum digs into Craftstrom's own FAQ wording, "Do I have to register this with my utility? Not in every State... Same as an off-grid solar system," and calls it "the weasel worded part," pointing out that comparing a grid-connected, load-following system to a genuinely off-grid one is either a mistake or misleading. Worth representing accurately rather than lumping it in with other brands' certification claims: it's a specific legal interpretation about non-backfeeding systems, not a claim about certification or state law.
Worth knowing too: the zero-export mechanism itself isn't unique to Craftstrom. Hoymiles' HiFlow Pro, one of the units in the table above, supports zero-export control through a compatible energy meter, and APsystems offers its own zero-export accessory for the EZ1-LV built around the same basic idea, throttling output using a smart meter or CT sensor reading the home's actual load. EcoFlow's STREAM appears weaker on this front; at least one owner reported no clean built-in zero-export option and had to throttle output manually. If Craftstrom's legal theory eventually holds up, there's no obvious reason it would apply only to their hardware, other brands using the same throttle-to-zero approach could plausibly make the same argument.
A few names that show up constantly in general balcony-solar buyer guides simply aren't available in the US market right now:
Anker SOLIX's balcony/Solarbank line is Europe and UK only
Enphase's balcony product exists only in Germany, with no US version announced
Growatt's NEO series is built around the European market, with no confirmed US certification path
If you are someone who starts shopping Amazon first, it's worth knowing that listing content isn't independently verified the way a certificate or datasheet is. A current listing for a bundled panel-and-inverter kit has been flagged by electricians on a professional forum for likely violating NEC Article 705, and questioned whether the inverter is genuinely UL-rated at all. Members of the DIY solar community have echoed the same skepticism directly. The listing is also still advertising the 26% federal tax credit as available, months after it expired, the same stale-marketing pattern already documented elsewhere in this research.
None of that means every Amazon listing in this category is unreliable. It means a product page is marketing copy, not a certificate. Check the actual datasheet, the actual certification body, and the actual manufacturer, before trusting sales copy.
Two brands in this research handle their EU-to-US transition very differently, which is worth knowing if you're ever comparing specs across regions yourself. Hoymiles' European 1-in-1 series and their US-certified HiFlow Pro LV line share identical physical dimensions, strong evidence it's the same board underneath, differentiated by firmware, plug type, voltage, and certification rather than the hardware itself. EcoFlow's STREAM line does the opposite: the European and North American units are genuinely different products, with different MPPT channel counts and different maximum outputs, not just a relabeled version of the same hardware. The takeaway is to never assume a spec sheet from one region applies to the product sold in another. Always find the region-specific documentation.
There's a strange split worth naming in that EcoFlow NA documentation too: their own installation manual lists user plug-in installation as the first, standard method, ahead of the professional hardwire option, which only comes up as an alternative for regions where plug-in isn't permitted. A major manufacturer is building its own onboarding around self-installation being normal, ahead of where the regulatory picture currently stands in most states.
In the interest of not overstating anything: a few points here are still open as of this writing. Hoymiles' actual certificate hasn't been pulled directly, only their own datasheet, though subsequent research points to it likely running through CSA Group under the legal entity name “Hoymiles Power Electronics Inc.” rather than a direct UL listing, worth checking there specifically rather than UL's own database. EcoFlow's UL 1741 status is currently sourced from a retailer listing rather than EcoFlow's own compliance paperwork. The inquiry to NEP about their UL 3700 discrepancy is still pending a reply. This page will be updated as those resolve.