HiFlow Pro. Photo: Hoymiles
Hoymiles has launched the HiFlow Pro, the first US microinverter certified to meet UL 3700, North America’s new safety standard for plug-in balcony solar.
Plug-in balcony solar gives homeowners and renters a smaller, less expensive alternative to a conventional rooftop system. The setup typically consists of one or more portable solar panels connected to a microinverter, which is then plugged into a normal electrical outlet.
Balcony solar is already hugely popular in Europe, particularly in Germany. Now, a growing number of US states are clearing a legal path for the technology.
As of July 2026, eight states – Utah, Maine, Virginia, Maryland, Colorado, Connecticut, Vermont, and New Hampshire – have signed plug-in solar legislation into law. New York’s legislature has also passed a balcony solar bill, but it was still awaiting the governor’s signature as of July 16. Nearly 30 states have introduced plug-in solar legislation in total.
The US now has a safety standard for plug-in solar
Plug-in solar has been stuck in a legal gray area across much of the US because existing rules were written for much larger rooftop arrays.
UL 3700 was officially published in December 2025 to address that gap. It’s the first North American safety standard specifically for plug-in PV systems, providing manufacturers with a certification route and utilities, local authorities, and consumers with a consistent safety benchmark.
That standard matters because a plug-in system sends electricity into a home through an outlet – the opposite direction power normally flows. Equipment, therefore, needs safeguards that prevent it from feeding electricity into the grid during an outage, which could put utility workers at risk.
What the HiFlow Pro microinverter does
Hoymiles’ HiFlow Pro microinverter is designed for residential balcony solar and uses maximum power point tracking (MPPT) to squeeze as much electricity as possible from connected panels as sunlight and weather conditions change.
Hoymiles lists static MPPT efficiency of 99.8% and dynamic efficiency of 99.5%, and the microinverter operates at low voltage, maximizing energy harvest under changing weather conditions.
Users can set it up through Bluetooth and wifi in less than a minute, according to Hoymiles. That plug-and-play approach is a big part of balcony solar’s appeal.
The 4-lb (1.8-kg) HiFlow Pro is 182 × 164 × 30 mm, has a NEMA Type 6 enclosure rating, and can operate in temperatures ranging from -40F to 149F (-40C to 65C). Hoymiles says it has also undergone 250,000 hours of reliability testing.
One 360W HiFlow Pro microinverter has an annual energy production of up to 721.08 kWh annual energy production.
Up to four HiFlow Pro microinverters can operate in parallel when connected to separate electrical outlets, allowing users to expand a balcony solar system to a total output of 1,200 watts and 2,403 kWh annual energy production, depending on state and local regulations.
“By introducing the first UL 3700-compliant plug-in microinverter in the US, we’re not only launching a new product – we’re helping establish a new benchmark for residential solar that combines simplicity, safety, and high performance,” said Hoymiles CEO Dr. Yang Bo.
Balcony solar isn’t going to power an entire house, but that’s not really the point. It gives renters, apartment dwellers, and homeowners who can’t install rooftop solar a relatively simple way to produce some of their own electricity – provided their state has gotten on board with the technology.
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