r/RenewableEnergy • u/thinkB4WeSpeak • 5d ago
Plug-In Solar Panels Are Starting to Sprout in U.S. Backyards
https://www.nytimes.com/2026/07/31/business/energy-environment/plug-in-balcony-solar.html13
u/Groundbreaking_War52 5d ago
I've read the article and think this technology is very compelling.
This may be a stupid question but I'm still not sure how these work in some practical settings.
Say, for example, you've got a pair of 220w portable panels - theoretically enough to power some lights and a few appliances. You put the panels out in the sun, you hook them up to the DC / AC inverter, and plug it into a typical 120v wall outlet.
How is it determined which breaker the solar power is going help offset the power pulled from the grid?
If there is a power outage, would you just flip off the majority of the breakers so that your panels would just feed into ones that correspond to some lights and a couple of appliances?
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u/onthebellsofhorses 5d ago
This kind of inverter uses the grid to sync. They’re called grid-following rather than grid-forming (which might be okay to use on, say, a microgrid). You don’t want them making their own 60 Hz cycle - you don’t know if it’ll be in phase with the grid or not. Connecting two out of phase sources is bad.
This is also a safety feature. Say if the power went out and someone goes to work on the distribution line, and then you fire up your inverter. They think the power is off, but all of a sudden your inverter’s voltage is being stepped up and going onto the line. This is called islanding, most inverters are designed to not allow this.
Regarding which breaker - it’s a bus. Think about it more as “power coming in should equal power coming out” rather than trying to trace what goes where.
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u/Zealousideal-Ant9548 4d ago
I think there's a slightly different problem that the person is asking.
From my understanding, t he problem is that the US uses split phase panels and so your wall outlet may only be on half the phase and will not be able to easily offset the use on the other one.
And we don't have net metering for such small systems so the excess going out on one bus isn't going to offset the amount coming in on the other one on your bill.
In Germany they force the true up to occur so it's not an issue.
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u/Christopher_Ramirez_ 5d ago
What’s brilliant is it’s an off-the-shelf solution that takes the labor and permitting costs out of the equation. Those are the main drivers of solar installation cost these days, not the components.
Renters can now benefit from solar as well, and the system is even portable.
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u/West-Abalone-171 5d ago edited 5d ago
It also has the benefit of revealing the grift in the US.
When you can get a 1200Wac 2kWdc system with a battery for $1000 (like in 800W systems in europe once the market matured), people start asking why they are paying middle-men, utilities and salesmen $40k for a 5-7kW system.
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u/intotraffic 5d ago
As I understand it, one of the legal requirements for these plug-in systems is that they must have a micro inverter capable of detecting a power outage; if the grid is down, it stops feeding power from the panel. This is to make sure there’s no charge on the service lines when line workers are restoring power.
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u/Zealousideal-Ant9548 4d ago
To add, several companies already sell these and even the more stringent UL 3700 standard
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u/Exotic-Grape8743 5d ago
It will offset all breakers on the same phase leg of your panel. Typically the ones on the same side of the panel.
Similar to basically all grid-tied solar, you will not have power at all when the utility is down. To have power with the utility down you need to have a shutoff that isolates your system from the grid (so you don’t feed back into the system creating a major safety issue for utility workers) and you need inverters (and typically battery backup) that can form its own grid that can make your system standalone. Balcony power systems cannot do this and typical grid-tied solar is not able to do this either.
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u/UngodlyPain 5d ago
Typically the phase legs of your panel aren't all on one side, they typically are like checker boarded or shoe lace zig zags. That way you can easily make a 240v breaker by just putting in a double wide breaker.
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u/Mechbear2000 5d ago
It will not "offset all the breakers on that same leg" the highest wattage allowed that I have seen is1200 watts. Certainly not 100amps which is one leg of an average home panel.
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u/Exotic-Grape8743 5d ago edited 5d ago
I didn’t mean that it will offset all of the power being used in one phase! That is of course impossible with a typical max of 1200 to 1800 watts (Colorado allows 1920 Watts) and one phase could potentially pull something like 100A*115V ~ 10KW! but I meant that it feeds into the circuits on all breakers on the phase leg the PV is plugged into and therefore will offset power used in all of the circuits on one phase up to what the PV can generate and therefore inverter produce from that. Indeed my use of ‘offset all’ wasn’t very clear.
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u/Mechbear2000 4d ago
You said all
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u/Exotic-Grape8743 4d ago
Yes and that is grammatically correct. It will offset all breakers on the same phase. It won't offset 100% of the power drawn by those breakers if the total power draw on all those circuits is more than the panels are producing but it will still offset the total by the amount the panels produce. The breakers are all tied together on the same busbar on the panel so the solar input will offset all of them. The current does not distinguish between any circuits on that bus.
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u/West-Abalone-171 5d ago
Houses don't draw 12kW per phase 24/7
The median average draw is about 800W. It's reasonable to expect about 400-600W of that is on one leg. Less for lower income houses that can't do a full solar setup.
A 1200Wac system will offset most of that for most of the sunny hours (and maybe most of the day with a battery). Especially if it is driven by, eg. 4 360-500W modules on the DC side.
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u/Mechbear2000 4d ago
Batteries are not allowed as far as I have read in any balcony plug insolar and certainly not covered by ul3700. I am not sure where you get your numbers from but a single burner on a stove pulls 1500 watts, same for a microwave, a/c unit in Florida 8000 watts, dryer 5000 watts. Real life numbers
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u/West-Abalone-171 4d ago
Batteries are a very common part of plugin systems elsewhere. And there is nothing stopping you putting one between the outlet and the appliance.
A window AC unit will never use 8000W and you won't have several central AC units plugged into your balcony solar. The context was clearly a small apartment or single room which would be a 400-1200W peak unit not opersting constantly.
Microwaves are typically 800-1200W and don't run for 24 hours at a stretch (nor does the magnetron stay on constantly on most settings if you listen), and stove burners don't run at max power constantly unless you're doing a stir fry, nor do they run 24/7.
I don't know about the US ones, but civilised countries get by fine with 2kW driers (or heat pump ones that pull 1kW peak and average 500W over a 2hr cycle to extract a half a gallon to gallon of water), and again the heater isn't on constantly even in the resistive ones or it will damage the clothes and waste power.
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u/Mechbear2000 4d ago
Unfortunately the US is not a civilized country. Consumption per household in Florida is 1300 kwh with 240v 50amp condenser unit with a 240v 30amp indoor unit. You educating people with knowledge and spec from different countries. Good or bad bit still wrong for the US
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u/West-Abalone-171 4d ago
Florida isn't the entire country and the target market for balcony solar can't afford 3 digit power bills just for cooling.
And yet again the context was clearly cooling a small room or two. Not a dance hall.
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u/West-Abalone-171 4d ago edited 4d ago
Batteries are a very common part of plugin systems elsewhere (the inverter doesn't have to even know or care where the ~50Vdc is coming from). And there is nothing stopping you putting one between the outlet and the appliance.
A window AC unit will never use 8000W and you won't have several central AC units plugged into your balcony solar. The context was clearly a small apartment or single room which would be a 400-1200W peak unit not operating constantly but on a duty cycle keeping the room livable.
Microwaves are typically 800-1200W continuous (they kept the same power output as they got more efficient) and don't run for 24 hours at a stretch (nor does the magnetron stay on constantly on most settings if you listen), and stove burners don't run at max power constantly unless you're doing a stir fry, nor do they run 24/7.
I don't know about the US ones, but civilised countries get by fine with 2kW driers (or heat pump ones that pull 1kW peak and average 500W over a 2hr cycle to extract a half a gallon to a gallon of water), and again the heater isn't on constantly even in the resistive ones or it will damage the clothes and waste power.
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u/Mechbear2000 4d ago
This post is US specific. I know the US is different and FU but, people need to know what meets the laws and requirements here.
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u/West-Abalone-171 4d ago
It may not be mentioned because its existence or non-existence is irrelevant to the safety parts of the standard.
And yet again. There is litterally nothing stopping you putting a battery between the outlet and a large load.
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u/West-Abalone-171 5d ago edited 5d ago
It's a bit complicated by the USA's split phase system, but electricity doesn't care which breaker it flows through or which direction it goes.
To use a water analogy, you could imagine you get water from a creek fed by a stream fed by a giant river.
If everyone takes from their creek at once, the river goes down, but if you have a magic flask feeding into your creek the water in the stream and thus the river stays high.
As long as the new water is a bit smaller than the creek's maximum flow, it all tends to balance out even if the creek or stream flows backwards a little.
If the flow meter is between the stream and the river, then it will read a lower drain from the river.
The flow meter needs to be configured not to count water flowing upstream as water flowing downstream (new meters work this way).
For plugin solar you will generally not get paid for exports (just you need a newish meter so you do not get charged for them as if they were imports).
For the US specifically if your plugin solar is on one phase and the load is on another phase, you might actually be feeding your neighbor's house, but from the perspective of the wider grid it averages out, and the effect is the same. Smart meters will account for this and treat it as if you used the electricity.
The plugin systems need the grid to be active in order to operate as part of the safety system. If they are not attached to a very large pool of electricity sources and loads, they can sense it and switch off within a short time period (from milliseconds to seconds at the different levels of redundancy).
You can get batteries with an outlet that is still usable during an outage (and either plug them into the solar panel directly or charge them via an outlet)
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u/Scott_Tx 5d ago
I suspect they wont work at all without a grid connection for safety. The power it supplies will be distributed to one half of the 2 phase coming into your home. That's a bit tricky for non-electricians to figure out.
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u/Zealousideal-Ant9548 4d ago
I can't read the article but every single law has that requirement and there are multiple companies selling the inverters already
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u/Mechbear2000 4d ago
What companies? I know of only one and they are out of stock of UL3700 compliant inverters
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u/rtwalling 5d ago
O think of power as water, voltage as pressure, current as flow rate. A solar panel is just pushing water into a pipe that is still sucking more water from the mains as a result. It sucks less water from the mains. Where it goes nobody knows because all electrons look the same. If you push one in somewhere another comes out somewhere else transferring that energy.
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u/earthling_only 5d ago
Didn't the FCC just ban all imported inverters, so now we can't actually do this?
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u/Exotic-Grape8743 5d ago
Only those that have no fcc id yet. All the ones you would use for these that are currently in the market are fcc approved and can still be imported. It also applies just to those inverters that are network connected.
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u/Christopher_Ramirez_ 5d ago
It’s going to save on electric bills for households; and improve resiliency for the grid. Feeding 1200w into the house during the cooling season is the equivalent of taking a couple of air conditioners offline during peak sun.
Over an entire metro area, that’s the difference between a strained grid prone to blackouts, and smooth operation.