The US’s first UL 3700 balcony solar microinverter is here

Plug-in balcony solar just cleared a big hurdle. Hoymiles has released the HiFlow Pro, the first US microinverter certified to UL 3700, a new safety standard published in December 2025 specifically for plug-in solar systems. Balcony solar setups use one or more small portable panels connected to a microinverter, which plugs into a regular wall outlet rather than requiring the wiring work of a rooftop system. Because that means electricity flows into a home's wiring in reverse, the new standard sets safety rules so the equipment can't feed power into the grid during an outage, which would endanger utility workers. Before this, plug-in solar existed in a legal gray area since electrical codes were built around large rooftop arrays.

The HiFlow Pro itself is a 4-pound unit that sets up over Bluetooth and wifi in under a minute, according to Hoymiles. A single 360-watt unit is rated for up to about 721 kWh of electricity a year, and up to four can run in parallel on separate outlets, scaling up to 1,200 watts and roughly 2,403 kWh annually, depending on what your state and local rules allow.

Whether this applies to your house depends on where you live. As of July 2026, eight states — Utah, Maine, Virginia, Maryland, Colorado, Connecticut, Vermont, and New Hampshire — have signed laws allowing plug-in solar, and New York's legislature has passed a bill awaiting the governor's signature. Balcony solar won't run an entire home, but it offers renters, apartment dwellers, and homeowners who can't do rooftop solar a simpler way to generate some of their own power, if their state permits it.