Why a breaker cannot protect you from your own solar panel
A circuit breaker sits at the panel and trips when too much current flows out through it toward your outlets. A plug-in inverter injects current at the far end of that same wire. If the wire is rated for 15 A and the breaker allows 15 A from the grid while the kit adds another 10 A from the balcony, a single outlet downstream can draw 25 A through 14-gauge wire, and nothing trips. UL's July 2026 guidance lists this first: "backfed current can push combined utility and PV current above conductor ratings without tripping the breaker."
That is the whole reason for the wattage caps in state laws. At 1,200 W on 120 V, the solar contribution is about 10 A. On a 20 A circuit with 12-gauge wire, the combination stays inside the wire's rating in almost all realistic situations. Germany's 800 W rule on 230 V circuits is the same math.
The three documented risks and what fixes each
| Risk | What happens | What removes it |
|---|---|---|
| Branch-circuit overload | Grid current plus solar current exceeds the wire rating with no trip | Small kit on a shared circuit (under ~400 W), or a dedicated circuit with nothing else on it; UL 3700 kits add overload limiting at the connection point |
| GFCI blinding | Ground-fault devices assume one-way flow; reverse current can keep one from tripping | UL 3700 requires ground-fault shutdown that works in both directions; outdoor circuits still need a GFCI |
| Energized plug blades | A grid-tie inverter not evaluated for user contact can leave the prongs live while the sun shines | UL 3700 requires blades to be safe within 1 s of unplugging; with a UL 1741-only inverter, cover the panel before unplugging |
The practical rules
- Under about 400 W: a shared 15 A outdoor GFCI outlet is acceptable practice, and it is the line Maine, Maryland and Colorado drew in their laws.
- Above 400 W: a dedicated 20 A circuit. To confirm an outlet is dedicated, switch off its breaker and check that nothing else in the home loses power.
- Never an extension cord, power strip, adapter, or a damaged or loose outlet.
- One kit per circuit. Some microinverter makers (APsystems) allow two units per branch circuit; more than that is unsafe on any residential circuit.
- Check your meter. Older non-net meters can run backward or count exported power as consumption. Your utility can tell you which you have.
- Buy a listed inverter. UL 1741 (or CSA/ETL to UL 1741) is the minimum; UL 3700 is what you want. See UL 3700 explained.
What anti-islanding does and does not do
Every legitimate grid-tie inverter shuts off within milliseconds when the grid disappears. This is the UL 1741 / IEEE 1547 "anti-islanding" requirement, and it exists to protect utility workers from a line that should be dead. It is important, and it is also irrelevant to the risks above: an inverter can be perfectly anti-islanding compliant while still overloading your branch circuit on a normal sunny day. Marketing that says "UL 1741 certified, so it's safe to plug in anywhere" is conflating the two.
Why some officials still say "wait"
The 2026 National Electrical Code does not recognize plug-in PV at all, and the next edition is not due until 2029. In a state without a plug-in law, a local inspector can treat a back-fed receptacle as a code violation even with UL 3700 equipment. In September 2026 the electrical inspector in Dover, New Hampshire urged residents to wait even though the state law had taken effect, because the building-code piece of that law is still pending certification of a national standard. Enacted laws in Utah, Maine, Connecticut, New Jersey and others solve this by statute. Check your state's page before you plug anything in.
Insurance and liability
New Hampshire's law exempts utilities from liability for damage caused by these devices and notes that they may affect homeowners or renters insurance. We found no insurer policy language on plug-in solar and no reported claim denial. The sensible move is to keep the certification and receipt, follow the circuit rules above, and disclose the equipment if your policy asks you to.