It doesn't make a power wave of its own. The kit's inverter follows the wave already on your outlet and pushes its current in step with it. When that wave disappears, it stops.
Grid120 V, 60 Hz
Kit adds6.7 A, in step
The inverter reads the outlet's wave and pushes current in step with it, 60 times a second.
Slowed down to be seen: one real cycle lasts 16.7 ms. The power-back wait is sped up. Amps at 120 V in full sun.
You don't match anything yourself. A plug-in kit's inverter is grid-following: it reads the voltage wave already on your outlet, 60 times a second, and pushes its current in step with it. It never makes a wave of its own. Your 120 V outlet carries one of your home's two hot legs, and the kit follows whichever one it's on. If the wave disappears, the inverter has nothing to follow; under IEEE 1547-2018 it must stop within 2 seconds and, by default, wait 5 minutes after the grid comes back.
U.S. homes get 120/240 V: two hot legs and a neutral from the utility's transformer. Each ordinary outlet uses one hot leg and the neutral. The kit follows the wave on its own outlet's leg and never needs to know about the other one.
Source: U.S. Department of Energy, Uniform Methods Project, metering protocols (2013 draft)
"NEVER try to power the house wiring by plugging the generator into a wall outlet, a practice known as “backfeeding.” This is extremely dangerous and presents an electrocution risk to utility workers and neighbors served by the same utility transformer."
U.S. Consumer Product Safety Commission, Safety Alert: Portable Generator Hazards
IEEE 1547-2018 is the U.S. standard for connecting inverters to the grid. If the grid around an inverter goes dead, it must stop feeding it within 2 seconds and stay off for a while after the grid comes back. NREL notes that for most home systems, manufacturers build this in. It protects the people who work on the lines.
Why it matters, in NREL's words: "the unintentional island could present a hazard to utility workers or other people in the area who are unaware of the electrically energized island." NREL primer
Voltage or frequency out of range, a sudden jump in the wave, or a change in its shape.
It makes small changes on purpose. The grid is far too big to move; if the kit can move the wave, the grid is gone.
It must stop sending power within 2 seconds, then stay off for 5 minutes by default once the grid is back.
Defaults from IEEE 1547-2018 as NREL describes them; a utility and a system owner can agree on other settings. Some state laws set their own outage rule: see each state's page.
To the inverter, a pulled plug is like a power cut: the wave is gone. Under the outage rule it has up to 2 seconds to stop, and during that time the plug's blades can still be live. An appliance's plug is dead the moment it leaves the wall; a solar kit's may not be.
That is one reason for UL 3700, the standard written for plug-in kits. UL Solutions' engineers list touch protection and automatic shutdown during power outages among its requirements. 3 of the 10 signed state laws name it: what each certification covers.
"if you unplug a PIPV system while the panels are exposed to light, the system is still producing power, and the metal blades can remain energized at hazardous voltage levels for up to two seconds, which far exceeds the well-established time limit to prevent an electric shock risk."
UL Solutions engineers in Solar Power World, Balcony plug-in solar panels (Feb 2026)
"Grid-interactive inverters used in PIPV systems are not evaluated for user contact safety. Accessible plug blades can become energized when exposed to sunlight, creating a shock hazard for consumers."
UL Solutions, Safety Considerations for Plug-In Photovoltaic (PIPV) Systems
Each law's certification wording, as we recorded it from the statute. The tags mark where it names outage protection or a standard that covers grid sync and shutdown.
UL or equivalent NRTL and UL 1741; NEC, IEEE 1547, State Building Code; outage protection
UL 3700 or comparable standard(s) by an NRTL; outage protection
UL 3700 or equivalent NRTL, and IEEE 1547-2018
Certified as a plug-in photovoltaic system by UL or an equivalent NRTL, plus an NRTL-certified feature that isolates the device to prevent backfeeding during an outage; must meet the current NEC and California Electrical Code
Labeled and listed by an NRTL; outage protection
Listed or certified to UL 3700, or to a comparable standard by an NRTL; or configured to the National Electrical Code as adopted in Maine
UL or equivalent NRTL; current NEC; outage protection
NRTL (29 CFR 1910.7); current NEC; outage protection
UL or equivalent NRTL
Certified by an NRTL to nationally recognized safety standards for distributed energy resources and plug-in solar systems
Tags: Outage protection, IEEE 1547, UL 3700, UL 1741, found in the wording above. A law without a tag can still require them through the certification it names. Each state's page has the full law and its source. General information, not legal advice.
Every signed state law names one. UL 3700, the plug-in standard, covers touch protection and shutdown in an outage.
What the certifications cover →
UL Solutions engineers in Solar Power World, Balcony plug-in solar panels (Feb 2026)
Following the grid does nothing for your wiring: the kit still adds current past the breaker.
The kit stops when the grid does. For backup power you need a system built to run on its own.
U.S. Department of Energy, Solar Integration: Inverters and Grid Services Basics
A generator makes its own power wave and can feed the street. Use its own outlets or a transfer switch.
U.S. Consumer Product Safety Commission, Safety Alert: Portable Generator Hazards
Free tools
Your state's law, what a kit would save at your address, and whether your circuit has room for one.
Its inverter locks onto the voltage already on your outlet and pushes current in step with it, the way the U.S. Department of Energy describes grid-following inverters: the grid provides a signal that the inverter tries to match. NREL says these inverters use a phase-locked loop to lock onto the grid. You don't set or adjust anything.
Not for syncing. U.S. homes get 120/240 V: two hot legs and a neutral. A standard 120 V outlet uses one hot leg and the neutral, and the kit follows the wave on whichever leg its outlet is on. What matters more is what else is on that circuit, because the kit adds current past the breaker: check it with our outlet tool.
No. With no grid wave to follow, a grid-following inverter shuts down. IEEE 1547-2018 requires it to stop within 2 seconds of losing the grid, and several state laws require an outage feature by name. For backup power you need a battery system designed to run without the grid.
A generator makes its own voltage and keeps running with the grid down, so plugged into a wall outlet it can feed the lines outside. The CPSC calls this backfeeding and warns it is an electrocution risk to utility workers and neighbors. A grid-following inverter has no wave of its own to send, and a certified one is tested to stop when the grid goes.
It can be for a moment. UL Solutions' engineers write that the blades of a plug-in kit can stay energized for up to two seconds after it is unplugged in sunlight, longer than is safe to touch. That 2-second window is the outage rule, which was written for line workers, not fingers. UL 3700, the plug-in standard, adds touch protection as a requirement.
That's on purpose. Under IEEE 1547-2018 an inverter that tripped off stays off for a return-to-service delay, 5 minutes by default, so the grid is stable before it starts feeding again.
Each electrical fact comes from the source linked beside it, read Oct 20, 2026. The numbers are worked out from those facts: one cycle at 60 Hz is 16.7 ms, so 2 seconds is 120 cycles, and a kit's current is its watts divided by 120 V (an 800 W kit adds 6.7 A). Timings are IEEE 1547-2018 defaults as NREL describes them, not measurements of any one kit. Law wording comes from each state's page, checked against the statute. General information, not legal or electrical advice.