What Is Plug-In Solar?

Plug-in solar is a solar panel with a microinverter attached that plugs into an ordinary wall outlet, feeding power backwards into your home’s circuits. It needs no roof, and in most of the places it is legal, no permit or electrician; Maine requires a licensed electrician above 420W. An 800W kit angled toward the sun makes about 960–1,200 kWh a year in decent sun, worth about $173–216 at the US average of about 18¢/kWh, or $125–360 across rates of 13–30¢, if your home uses all of it. Hung upright on a balcony railing, it makes roughly 40% less.

It is also called balcony solar, and in Germany a Balkonkraftwerk; the federal grid regulator’s energy register lists about 1.5 million of them in operation (October 2026). The US is several years behind on adoption and roughly a decade behind on regulation, which is the single most important thing to understand before you buy one.

What is actually in the box

A plug-in solar kit is three things, and the third is the one that makes it different from every other solar product.

• One or two panels. Usually 400–500W each, rigid, roughly 5½ feet by 3½ feet. Physically the same panels that go on roofs.
• A microinverter. A small box, often bolted to the back of the panel, that converts the panel’s DC output into household AC.
• A cable ending in a standard plug. This is the whole trick. Rooftop solar terminates in a wired connection to your service panel. Plug-in solar terminates in the same plug shape as a lamp.

Mounting hardware for a railing, a wall or a ground stand is usually included or sold alongside. Some kits add a battery, which changes the economics substantially and is covered further down.

How it feeds power into your home

Electricity flows to wherever it is being consumed. When the panel is producing 400W and your home is drawing 900W, the panel supplies 400W of that and the grid supplies the remaining 500W. Your meter only ever sees the difference. Nothing has to be told to do this; it is simply how a parallel circuit behaves.

That is also the limitation. Plug-in solar reduces what you import, and does nothing else. It has no way to store surplus, and in most cases no way to sell it.

Your baseline is the floor your house never drops below: the fridge, the router, standby draw on everything with a clock in it, and a well pump or sump pump cycling. In most homes that is 200–500W around the clock. A single 400W panel spends most of a sunny day producing less than that, which means almost everything it makes is consumed on site. That is the case for starting small.

How the microinverter syncs with the grid

Household power is alternating current: a sine wave that swings between about +170V and −170V and back sixty times a second (60Hz). The 120V figure is its RMS (effective) value, the steady voltage that would deliver the same power; the plain average over a full cycle is zero.

A second source can add power to that circuit only if its output matches the wave. The microinverter measures the grid’s voltage at the outlet and feeds current in step with it, at the same frequency and with peaks and troughs aligned, adjusting continuously as the grid drifts. Out of step, it would push against the grid instead of adding to it.

That makes it a grid-following device: it can add to a supply that already exists but cannot create one. When the grid goes down there is nothing to follow, and anti-islanding protection stops it within 2 seconds (IEEE 1547 / UL 1741; see the safety section). That is why a plug-in kit produces nothing in a blackout, however sunny the day. Rooftop systems work the same way, through one string inverter or a microinverter per panel. Plug-in kits use small microinverters because they are compact, keep the DC voltage low and put out plug-ready 120V AC; one microinverter often serves two panels.

What your meter does

Your utility meter registers only the net flow, as in the 900W example above. What matters is how it handles the moments when the panel out-produces the house and power flows out through it:

• Old electromechanical meters, the kind with a spinning disc, can turn backward. That credits you at the full retail rate under an arrangement your utility never agreed to.
• Digital and smart meters do not turn backward. Depending on how the utility has set them up, they record exported energy on a separate register, ignore it, or add it to the energy you bought. In the last case, every exported kilowatt-hour raises your bill.

Ask your utility which applies to your meter before you buy, especially if the kit is larger than your baseline load. A state plug-in law does not settle this on its own: Utah’s HB 340, covered below, keeps these devices out of net metering, so exports earn no net-metering credit. Connecticut’s law requires kits to carry a warning that output beyond what the home is using will be billed as usage unless the meter allows net metering, and Vermont’s allows plug-in kits only on homes with a smart meter.

How it differs from rooftop solar

The comparison people expect is “a small version of rooftop solar”. It is not. Rooftop solar is a capital improvement to a building you own, sized to erase a bill. Plug-in solar is an appliance you buy, sized to shave one, and you unplug it and take it when you move. They answer different questions, and the reason plug-in solar exists is that tens of millions of US households cannot answer the rooftop question at all.

What it realistically saves

Annual output depends on panel wattage, sun hours and mounting. The output figures below assume 4–5 peak sun hours and a well-oriented panel tilted toward the sun. As a check, the PVWatts model described below puts an 800W array tilted 30° south in Kansas City at about 1,170 kWh a year, inside the range for two 400W panels. The dollar columns value every kilowatt-hour at the rate shown, so they assume your home uses all of it. In practice a kit sized to your baseline uses about 80–90% on site, and anything exported unpaid comes off these figures. The middle column uses 18¢, close to the US residential average of 18.31¢/kWh that the EIA reported for July 2026.

Two things fall out of that table. The first is that your electricity rate matters more than your hardware. The same kit is worth roughly two and a half times as much in California or Massachusetts as it is in Washington or Louisiana. Check your own rate before you check any product page; it is on your bill as the total divided by kWh used, not the headline supply rate.

The second is that a battery does not increase output. It shifts when you use the output, which is worth money only if you are on a time-of-use rate where evening power costs materially more than midday power. On a flat rate, adding a battery to a plug-in system lengthens the payback rather than shortening it.

What affects daily output

A 400W panel is rated at 400W under laboratory test conditions and makes less on almost every real day. Where and how you mount it moves the yearly total more than most buyers expect. The direction, tilt and season figures below come from PVWatts, the free solar model from the National Laboratory of the Rockies (formerly NREL), run on October 9, 2026 for an 800W array with 14% system losses in Los Angeles and Kansas City.

A railing mount is usually a compromise. A panel hung flat against the railing is convenient and secure, but the table shows what it gives up. Facing south, the penalty is smaller farther north, where the sun sits lower in the sky. To model your own spot, enter your address in PVWatts with your kit’s panel watts as the system size, then set the tilt (90° for a panel hung upright) and the direction it faces. Our solar sizing guide works through these losses in more depth.

Working out the savings for your own balcony

The savings table above gives ranges. To get a figure for a specific kit, three inputs do the work: its rated watts, the peak sun hours where you live, and a derate for everything lost between the panel and your outlet. Annual output is rated watts × peak sun hours × derate × 365 ÷ 1,000.

The worked case here is deliberately cautious for a panel tilted toward the south: 4.2 peak sun hours, inside the 4–5 range used above, and a 75% derate for heat, wiring, inverter and dirt losses. For 800W of panel that is 800 × 4.2 × 0.75 × 365 ÷ 1,000 = about 920 kWh a year, just under the low end of the savings table. Output moves in step with sun hours: at 3.5 the same array makes about 770 kWh, at 5.5 about 1,200. A panel hung upright on a railing makes much less than any of these figures (see the daily-output table), so for that mount run your address through PVWatts at a 90° tilt instead.

Payback then follows from the price. The three kits below are sold in the US, at the sellers’ prices on October 9, 2026. Bright Saver’s are its at-cost prices for members, who pay $29 a year, not counted below; without membership its one-panel kit is $499. The figures assume 85% of the output is used in the home, the middle of the 80–90% range above.

Price per rated watt does more of the work than the brand: the 360W Bright Saver kit costs members about $1.15 a watt, the 800W Craftstrom Eco-Line about $1.88. Run payback on the price you will actually pay.

The safety argument, and why the objection is real

The objection to plug-in solar is backfeed: a household circuit is designed for power to flow one way, from the breaker panel out to the outlets, and its breaker is sized to protect the wiring on that assumption. Push power in from the outlet end and you can in principle load a circuit beyond what its breaker will trip on, because the breaker only sees current passing through it, not current injected downstream of it.

That raises two hazards: energizing a line that should be dead, and overloading the circuit. Compliant kits address them in three ways. Anti-islanding answers the first. The output cap shrinks the second without removing it, which is why the circuit you choose still matters. Certification is how you know the first two work:

• Anti-islanding. Every compliant microinverter monitors the grid and stops feeding power within 2 seconds if it disappears, the limit set by IEEE 1547, which UL 1741 certification checks. This is why a plug-in system gives you nothing in a power outage — the shutdown is the safety feature, and it is not optional or defeatable. If you want power during an outage you want a battery, not a panel.
• Output limiting. Kits sold for this purpose cap their output; the German limit that shaped the category is 800W. The cap limits the overload risk but does not remove it. The circuit breaker cannot see the kit’s current, so with other loads on the circuit, part of the wiring can carry the 15A the breaker allows from the grid plus about 6.7A from an 800W kit. Use a dedicated or lightly loaded circuit, and have a licensed electrician check it if you are unsure what else shares it.
• Certification. The microinverter is the safety-critical component, and it is where the certification question actually lives.

Where it is legal in the US

Utah was the first state to explicitly legalize plug-in solar, via HB 340 in 2025. Its law covers devices of up to 1,200W that plug into a standard 120V outlet, meet the National Electrical Code and are certified by UL or an equivalent laboratory. Those devices need no interconnection agreement and no utility approval or fee, and they are not part of net metering. By September 2026 at least nine states had enacted plug-in solar laws, and California made it ten on September 30, 2026. Caps, certification rules and start dates differ by state, and several of the 2026 laws do not take effect until 2027.

Two details matter more than the headline cap. Most caps cover the home, not the kit: Maine, Virginia, Vermont, New Jersey and California add up every kit at the same address, meter, customer or dwelling, and Colorado, Maryland, Connecticut and New Hampshire allow one system only. And several states want notice: Virginia and Maryland before you install (Virginia gives the utility 15 days to review the form), Maine within 30 days above 420W, while Colorado, New Hampshire and California let the utility ask for it. Notice is not permission; all ten laws bar the utility from requiring its approval.

Status as of October 9, 2026. New York’s legislature has also passed a plug-in solar bill, the SUNNY Act; in early October 2026 it was still awaiting the governor’s decision. Laws change each session, so check your own state’s current rules before you buy.

Outside a state with an explicit exemption, the position is genuinely unclear rather than simply prohibited. A plug-in system is small enough that most utility tariffs never contemplated it, so it tends to fall between rules written for appliances and rules written for generators. What that means practically:

• Check your own utility’s interconnection rules first, not a general article, including this one. They differ widely between neighboring utilities. Our plug-in solar permits guide lists the questions to ask yours.
• Renting adds a second permission. Even where the state and utility permit it, your lease and your landlord govern what you may attach to a balcony railing. Freestanding ground mounts and window-ledge mounts exist partly for this reason.
• An HOA is a third. Some states have solar access laws that limit what an HOA may forbid; whether those laws cover a plug-in system rather than a roof array is often untested.

We are not lawyers and this is not legal advice. The honest summary is that the hardware is mature and the regulation is not, that the direction of travel is clearly toward permission, and that the answer depends on your state, your utility and your landlord in that order.

What to look for in a kit

The last row is the one people skip. If your utility’s answer takes six weeks to obtain, a 30-day return window is not long enough. Buy from somewhere that will take it back after you have the answer.

On orientation: true south is best in the northern hemisphere, but the penalty for facing west is smaller than most people assume: 16–21% of annual output in the PVWatts runs above, not half. A west-facing balcony can even be preferable on a time-of-use rate, because it produces into the expensive evening peak. Our solar panel angle calculator works out the tilt for your latitude, and the plug-in solar section covers the kits themselves.

Who should not buy one

Three groups, and the site would rather say so than sell to them.

• Homeowners with a good roof, a sunny site and net metering. If you can put 8kW on a roof and be paid for the surplus, that is a fundamentally better deal per dollar. A plug-in kit is what you buy when the roof is not available.
• Anyone buying it for outage backup. Anti-islanding means it switches off the moment the grid does. This is the most common misunderstanding of the product, and it is not a limitation that a bigger kit solves. What you want is home battery backup.
• Anyone on a cheap flat rate with a shaded balcony. At 11¢/kWh with a north-facing wall, the arithmetic does not work and no amount of enthusiasm fixes it. Run your own numbers before you run anyone else’s.

If none of those describes you — you rent, or your roof is shaded, wrong-facing, or not yours to touch, and your rate is above about 18¢/kWh — plug-in solar is one of the few pieces of energy hardware that pays for itself and travels with you when you move.

Frequently asked questions