Balcony solar, explained
Plug-in solar is a small panel-and-microinverter kit that plugs into an ordinary wall outlet: no roof work, no electrician, and in most states that allow it, no permit. Ten states have a signed law as of October 2026, Utah, Maine, Virginia, Colorado, Maryland, Connecticut, Vermont, New Hampshire, New Jersey and California, though California's doesn't start until 2027-01-01. CESA puts the payback at roughly four to thirteen years, depending on your electricity rate and how much sun the panel sees. The number that matters most isn't the panel's wattage: it's whether something in the house is running when the sun is.
How it works
A plug-in system is one or two panels, rated anywhere from 200 Wp to about 1,600 Wp, wired to a microinverter that converts the panel's DC output to grid-synchronized AC and shuts down when it stops sensing the grid, so an unplugged cord is never live. The cord goes into a standard outlet on the circuit you want it to feed. When the panel makes more than that circuit is drawing, the surplus flows back out through the meter; when it makes less, the grid fills the gap.
Is it legal where I live?
It depends on your state. Ten states have a signed law as of October 2026, each setting a wattage cap and exempting the device from the normal interconnection process below it. New York has passed one and is waiting on the governor's signature; Massachusetts has two competing versions stuck in conference committee. Everywhere else, your utility's ordinary interconnection rules apply the same way they would to a rooftop system.
See the full state-by-state tablebefore you buy anything.
What it costs and produces
CESA puts a well-sited 800 W system at roughly 700 to 1,051 kWh a year, a 10 to 15 percent capacity factor, and a simple payback of 4.4 to 13.3 years depending on your electricity rate: 13.3 years at 15¢/kWh, 4.4 years at 30¢/kWh. A typical kit runs about $1.75 per watt in the US. None of that accounts for the power you don't use when it's made, which usually earns nothing.
See does it pay for the full table and a calculator for your own state and rate.
Try the calculator →Plug-in batteries
A plug-in battery stores the midday surplus a panel alone would give away and discharges it into the evening, when usage and prices are usually both higher. Maine's law explicitly covers a plug-in battery system; California's explicitly does not; the other eight laws in this guide are silent on it. EcoFlow's STREAM Ultra, the main product sold in the US as of mid-2026, ships only to Utah so far.
See plug-in batteriesfor what's covered, what's sold, and whether one pays for itself.
How to install
Every law in this guide requires the device to isolate itself during an outage and to carry NEC and NRTL certification; UL 3700 is the standard written for exactly this, though no complete system had been certified under it as of August 2026. A handful of states lower the bar further: Maine allows a 420 W self-install with no electrician, and Maryland and New Jersey exempt systems under 400 W from the certification step entirely.
See how to install for what's in the kit, where it goes, and what changes by state.
Why timing decides whether it pays
No US law in this guide pays you for the power a plug-in panel exports; the device sits outside net metering everywhere it's addressed at all. So the entire return comes from using what the panel makes while it's making it, shifting a water heater, an EV charge, or HVAC into the hours the sun is up instead of just the hours your rate is cheapest. That's the scheduling problem Hungry Machines already solves for time-of-use and dynamic rates; a registered plug-in system becomes one more input to the same nightly plan. Read the full guide onplug-in solar and load shifting.
Get started free →Outside the US
Germany is the mature market, where a 2024 reform raised the inverter limit to 800 W behind up to 2,000 Wp of panels and cut the paperwork to one registry entry. Its registry held about 1.29 million systems as of March 2026, up from roughly 480,000 before the reform. The default there is unpaid acceptance of any surplus; a feed-in tariff route exists at 7.78¢/kWh in 2026, against 30–40¢/kWh retail, so self-consumption wins there too.
Renting with a window AC?
Plug-in solar needs an outlet and, in most states, a lease that allows it. If what you actually have is a window AC or mini-split and no interest in panels, theSmart Satellite does the same scheduling with nothing to plug in or mount: it talks to the remote the unit already has and runs the nightly plan on its own.
Frequently asked questions
What is plug-in solar?
Plug-in solar is one or two small panels, usually 200 to 1,600 watts total, wired to a microinverter that plugs into a standard wall outlet instead of being hard-wired by an electrician. It feeds whatever circuit it's plugged into directly: the house uses the power before it uses anything from the grid, and any surplus flows back out through the meter. Ten US states had signed a law allowing it, with conditions, as of October 2026; elsewhere the ordinary rules for connecting any generating device apply. Germany is the most mature market, with roughly 1.29 million registered systems.
Does plug-in solar lower my bill without me doing anything?
Not reliably. A plug-in system earns nothing for power it exports in nearly every US state and in Germany, so a watt made while nobody's home and nothing's running is a watt given away for free. The return depends on something in the house drawing power while the sun is up, a water heater, an EV charger, HVAC. CESA's payback range of 4.4 to 13.3 years assumes the owner is already doing a reasonable job of that; left entirely alone, a system can land well outside that range.
Can I use plug-in solar if I rent?
It depends on your state and your lease. New Jersey's law bars a landlord from prohibiting a tenant who pays their own electric bill, including on a leased balcony or patio. Virginia bars landlords of more than four units from an outright ban, though they can set reasonable rules on size and placement. Most states say nothing about tenants specifically, which leaves it to the lease and the building. If a panel isn't realistic where you live, the Smart Satellite brings the same scheduling to a window AC with nothing to plug in or mount.
How does Hungry Machines use a registered plug-in system?
It becomes one more input to the nightly plan. Hungry Machines forecasts your panel's output from a weather forecast for its tilt and azimuth, and sharpens that forecast against a production sensor if you connect one. Every sunny hour discounts the price of running your other machines, your EV charger, water heater, HVAC, or battery, by what exporting that power would have earned instead, which is usually nothing. The plan schedules those machines against the discounted curve the same way it already schedules them against your utility's time-of-use or dynamic rate.
About Hungry Machines
Outsmart your electric bill - Hungry Machines Energy provides an energy management system that shifts HVAC, EV charging, home batteries, and other electric loads to cheaper hours for homes and buildings with solar power or variable electricity rates.