Solar panels are getting cheap enough for grid hook-ups, installation and regulatory approval to become the bottlenecks.
Plug-in solar is suboptimal in many ways, but it does sidestep a lot of those hurdles. Not too surprised to see it on the rise.
Another thing that might be worth keeping in mind is that plug-in solar panels are often installed vertically - i.e. balcony solar. In which case the peak of the panel's generation is offset to the edge of the typical "duck curve". If it gets popular enough to affect the grid, it might get the solar-induced demand slump larger, but make the edges even sharper.
Would that make grid scale battery storage with its instant response even more important?
That's why I installed my 13kw system myself. I saved a ton of money, assuming you don't equate time with money, otherwise it will have cost me a fortune. It was a great learning experience, and quite fun.
That’s absolutely insane. I just had 5400Wp of panels installed with 15kWh of battery storage and it was ~€12k total. The battery was a bit over half of the costs. That’s the total cost, hardware and labour.
No need for permits for rooftop solar and the only dealings I had with the energy company was filling out an online form to register it. Took maybe 2 minutes.
The US is getting fleeced! 8 years ago it cost me about $10k AUD to install 6kW. Yes, it came with a $2.8k subsidy but still we are talking about a third.. 8 years ago.. And I paid extra for a Fronius inverter.
Your numbers are way too high. I live in the very expensive San Francisco Bay Area and my system 6kW before federal tax credits was 16k to install in 2021. After credits it was < $12k. I have a friend in Tucson AZ who just paid $12K for a 4kW system with no subsidies.
I did not add a battery because at the time it would have doubled the price. Also, because I have net metering the battery never pays itself off.
Rooftop solar generally requires professional installation. Balcony solar, as discussed in the article, does not require professional installation and simply plugs directly into an outlet.
With the plugin solar I can imagine people in single family residential installing them on both sides of fences and gates to get an around the day benefit.
Also, with the price of solar panels decreasing below most (wood?) building materials with way higher durability, no paint required, why wouldn't it replace most sun facing siding applications aside from being "ugly".
The plug in solar systems are small and usually mounted in ways that don’t capture as much energy as the same panels mounted on a roof. These systems aren’t going to get popular enough to make a big difference in anything.
I think it’s nice that they’re available for people to do some small scale offsets, but I think they’re more of a gateway to better solar installations. They also send people down the path of investigating battery storage add-ons, which might actually be a better long term solution for everyone.
If we can get to a point where we can buy plug-in batteries that are subsidized by requiring coordination with the grid, the power companies could get distributed, controlled battery storage to work with their demand curves. This can already happen with the bigger permanent install batteries.
The biggest problem with plugging a generator into an outlet is you need a double ended cord. If you use everything correctly they work fine, but there are too many ways things can go wrong. The most obvious one is you plug everything in, start the generator, and the trip over the cord on you way back inside, thus sending the live male end flying toward you. Once in a while a kid will see these dual male plugs and plug them in - lots of ways things can go wrong here.
There is also the problem of backfeeding, but this is more theoretical - even if you know to limit your power use, your neighbors won't and so your generator will trip its own breaker. Linemen are taught to either treat power lines like they are live, or to short them to ground - it can happen they don't do this and you kill a linemen, but still not as big a worry as it is made out.
They make generator "inlets" that sidestep all these problems when used correctly. Most common I've seen is a block so you can't have the inlet and the main breaker both on at once.
> There is also the problem of backfeeding, but this is more theoretical
it is not theoretical from the POV of power company employees working on their lines. the power goes out, they go to fix the equipment or wiring, and if the inverters connected to the grid have not shutdown, there could be 10s of kW to even MWs being backfed into the system they are working on.
that's why in the US at least, grid-tied inverters are required to have protection against this. if they do not see power from the grid, they shutdown (and rather quickly).
It's not so much being unplugged as it is sensing whether the mains power is down. If it is, they stop backfeeding immediately, just like hardwired solar inverters do.
If this weren't done, there would be risk of electricution to anyone working on wiring in the house or on the utility distribution network.
Furthermore, the danger of backfeeding is if you do it in a power outage and you start to power your neighbors' houses. It'll overload your generator and create a hazardous situation for anyone working on the wires. (This is why you're supposed to install either a generator switch or interlock. I have one that only allows me to energize when my main breaker is turned off.)
But how do they do it technically? Some countries require anti-islanding devices for grid connected solar, these are around $1000. That alone is much more expensive than the $300 plug in panels.
In addition to the electronics that others mentioned, they also have limited amperage. That way even if you are pulling from your mains power and the solar at the same time, your circuit hardware shouldn't melt or catch fire.
How do these work when plugged in to only one of the split phases on a US-style 120 system? Because I'm a nerd, I know which legs of the phase go to which outlet in my house, but I don't expect everyone to pay attention to that. I assume something has to take that into account somewhere.
There is no problem and so nothing needs to account for it. A split phase is just a transformer with three windings, and one is connected to the other. We call one side (high voltage) the primary, and the other two secondary, but the transformer doesn't care at all, it can send power either way (there are limits but we are well under the maximum rating of the transformer so we can ignore them). If you only draw 240 volts then the two connected windings act as a single secondary, if you only draw 120 then one of the two secondaries provides power. Any other combination - the transformer doesn't care.
U.S. homes typically get power through two hot wires. The hot wires are connected to a utility company's transformer and are 180 degree out of phase. Each supplies 120 volts.
The power from the plug-in outlet is consumed by any devices connected on the same circuit first. Any extra flow through the electric panel’s bar connecting the circuits on the same 120V phase, where the devices on them use the extra next. Any excessive power flows back out of the meter on the 120V phase line on your service connection to the transformer at the street block. The transformer might feed it to your neighbors. In any case the transformer feed electricity to the other 120V phase line back into your service connection, the meter, the panel, the other split phase bar, the circuits on it, and the outlets on them. The devices on the other split phase circuits technically are not using the plug-in power directly.
Most modern meters measure electricity going in and out on both split phase lines as a whole, as a net amount, so the electricity consumed in the other split phase circuits is offset by the plug-in power. However some old meters add the outgoing electricity up as consumption so you are paying for the electricity fed into the grid. Call your utility company to make sure.
Also, unless you have a net metering agreement with your utility company, you won’t get paid for any excessive electricity fed back into the grid.
I doubt it matters. The power company also theoretically has to deal with houses where they coincidentally draw more from one side of the split than the other. But I suspect it all averages out, and the contribution of a couple plug-in panels in a bunch of houses won't change anything.
It backfeeds onto the grid and becomes the utility companies problem to deal with. This is similar to them dealing with a house that is an unbalanced consumer between the legs.
To my understanding, it is basically a non-issue at residential voltages. To be a problem it would require all the houses on a transformer (there are typically just a few for each transformer) to be unbalanced significantly in the same direction. That would be the end of it, too, because the 240V split only happens at the transformer.
My concern is what happens to grid stability as we replace synchronous generators, with their enormous rotational inertia, with thousands of grid-following inverters. They can all phase-lock to 60 Hz, but without enough inertia, what keeps that frequency stable during sudden changes in load or generation?
I don’t see many (any?) plants using them, is the technology there yet? Genuinely curious.
And on an unrelated note, it seems that hybrid power plants are becoming a talking point now and they seem to make a lot of sense. Like covering dams with solar panels saves on water, make PVs cooler/work more efficiently and you don’t need to worry about permits/building more grid connections because you can simply slow down hydro during daytime (and get along with grid following inverters just fine).
I hope the next step for this is plug-in battery storage. All the on-grid battery hybrid inverters I can find in the USA are either single leg 120V or 12kW for $5k. I just want like 3kW dual-leg with support for a dozen kWh of batteries
I've seen setups where they put a 48v battery between the solar panels and plug-in micro inverter. No idea how this impacts efficiency or if there's any safety concerns though.
Yeah it seems like the inverter manufacturers don't see demand for that. I was thinking maybe the Victron Multiplus-II 2x120 could be paired for 240V output but I was wrong, that's only on grid power, it won't make 240V from battery.
Obviously the inverters and pairing technology exist, but I don't know where to buy one retail.
Victron devices on sale in Europe/UK all do 240V output. I've seen someone do a boat build in the USA with Victron hardware that included 240V circuits (because the builder was a UK/US person, and they wanted both 120 and 240 "normal" circuits).
Does this seem like a bad idea from a safety perspective?
With fixed solar installs you're likely to find some kind of switch or labeled breaker to disconnect. The system is designed with a central "power in" that's (hopefully) obvious/proximate when you're standing in the breaker room.
These things could be injecting power anywhere, so you need to know they're there (which may be less apparent than roof/field panels) and go around and pull the plug(s). Relevant to electricians, firefighters, etc.
Yes, there are serious safety concerns. Both islanding, which is where a circuit is hot when it shouldn't be, and from a circuit overload.
Your circuit breaker protects your circuits by putting all the load (eg your microwave) on one side, and your supply (mains power) on the other. If too much load is present, the circuit breaker trips.
However, plugin solar puts invisible supply on the load side, which your circuit breaker cannot see. Let's make an absurd example so you can see what the problem is, then scale it back.
Imagine someone buys 5 panels that can each supply 5amps. They plug them into outlets on a 40 amp circuit. They then proceed to run their toaster, microwave, vacuum, and hair dryer. They can draw 65 amps through the wires before the circuit breaker trips. (40 from mains, 25 from the panels)
Let's say they had a good electrician who installed 6AWG wiring on that circuit, which is rated for 50 amps. The circuit breaker used to trip at 40, so no problem. But now up to 65 can go across the wires and suddenly you are exceeding rating for wires.
Now you might say, "most of these are 3.5 watts, and they clearly say don't use more than one". But I say that's a "good intentions solution". We should make it mechanically impossible to do the wrong thing. Maybe these panels could try to communicate over the electrical wires, and if they detect a signal from another panel they should self limit. Maybe we need to rethink circuit panel design. But as it stands people will absolutely buy one of these, decide they love it, and then buy 4 more.
These rely on seeing a grid frequency to follow when they output power. If you shut off the breaker for the circuit they're on, no grid frequency to follow, and they shut off their output. When unplugged, the plug never has any voltage on it.
Perhaps also useful would be plug in batteries, especially if one has variable rates. Charge when cheap, discharge when expensive.
One constraint on these I've read is that if you have sources and sinks on the same circuit, you might overload the line without tripping the breaker at the box. If I'm understanding this correctly this has caused them to limit the power of plug-in solar to a fraction of what a single circuit could potentially carry.
Yes, it's designed so that total current and potential heat problems are still within safety margins of circuits built according to code. In most of Europe, one regular (or upper end of regular, depending on country) residential circuit can supply 3.6 kW (230 V * 16 A = 3680 W), so 800 W are "just" a 20% overload.
There are advantages to distributed infrastructure as well! You mentioned one of the biggest disadvantages.
I am thinking along the line of:
- You can just do it / upgrade it etc
- Robust against central failures for various reasons
- Resistant to those in charge of centralized infrastructure abusing their monopoly
Utility solar is also distributed if there is enough of it installed to matter for discussion. A single installation is such a tiny share of the electric load that we can ignore if for all reasons you care about distributed. (or care about solar for that matter - it is a drop in the ocean for the environment)
Utility-scale solar might be cheaper but doesn't make my house resilient to grid failures. It also only benefits me when the grid is upgraded enough that ... well, it benefits me.
Plug in solar doesn't make your house resilient to grid failures either. You would need an inverter that can generate an AC output without having an existing one to follow; a disconnect to isolate you from the grid during an outage, batteries to smooth the output, an electrician to install it, and an inspection to certify that it was all done correctly.
If you are going through all of that, there is not much benefit to plug-in solar instead of traditional.
It is easier to find a million people with a few hundred euros and a sunny balcony than finding one dude with a few hundred million euros and land on which building a solar farm is permitted.
18.8% Nuclear and 8.4% solar (more than double the national average!)
OUC on the other hand has less than 3% Nuclear (generated / purchased from FPLs plant on Hutchinson Islans!) and <6% solar, with a massive 24% still being generated by coal! (FPL demolished their last coal plant ~8 years ago in Indiantown, I watched it live!)
So while FPL is technically for profit and OUC is not... FPL is cheaper and greener than OUC.
I say this as a long time Florida resident who remembers when FPL truly sucked in many ways. They’ve, demonstrably, put in effort to make electricity greener and cheaper here in FL. (Even with all of their efforts against home solar).
Isn’t it backwards? If everyone had a little bit of home generated power, then the actual energy part of the bill becomes smaller, and the cost of transmission becomes an even greater fraction of the total cost.
And since transmission cost is typically bundled with the energy cost, it means the final retail energy price has to go up to cover the transmission cost.
Where I live we have Time of Day electricity pricing where the prices jump 2-3x during high demand. Panels conveniently produce the most power around this time, so this can save people money.
Utility companies are not incentivized to lower prices because it means less money for them. Do you remember when power companies told people to conserve power and then people successfully did this? And then they raised rates because they weren't making enough money? This happens in California ALL THE TIME. I've lived here 30 years in Silicon Valley and it's the biggest scam that no one talks about. It happens with electricity and water. With water its even more egregious because they told us to conserve water because of the "drought" but once the drought was over, they raised rates because people weren't using enough water. My connection fee to water is over $100/month without spending a drop of water. That's why I stopped conserving water and water my lawn every single day because it turns out that my water costs are only about 1/3 of the actual water bill costs so fuck it!
It's the same playbook over and over again, there's no incentive to lower rates at all because it's an easy way to make money over an entire population of tens of millions of people.
Now PG&E is fighting to charge solar panel owners $100+/month just for the privilege of being connected to the grid. That would make having solar panels even more expensive than not having solar panels which is utter hypocrisy but no one seems to care or point this out. It's a complete and utter scam.
EDIT: I forgot to mention last year the rates were $0.37-0.45 per kWh, until this year when they implemented a base fee of $25/month, so they lowered it to $0.33-0.45/kWh. Rates in Nevada are 1/4 of that.
2015: $0.17-0.33 per kWh
2020: $0.24-0.38 per kWh
so prices have more than doubled in 10 years. Fucking criminals.
I live in Florida, and I'm building a water battery, so I can freeze it at night when electricity rates are cheap, and use it to cool the house during the day.
The day after the system goes live, they'll probably announce flat rates for any time of day, just to f' with me. :(
By that logic literally everything should be distributed. That's going to be a big undertaking to re-architect our entire civilian infrastructure against that.
I'm not saying you're necessarily wrong, I just don't see society taking that measure until it's either 1) cheaper, or 2) the threat moves from being just a threat to reality.
Solar panels are getting cheap enough for grid hook-ups, installation and regulatory approval to become the bottlenecks.
Plug-in solar is suboptimal in many ways, but it does sidestep a lot of those hurdles. Not too surprised to see it on the rise.
Another thing that might be worth keeping in mind is that plug-in solar panels are often installed vertically - i.e. balcony solar. In which case the peak of the panel's generation is offset to the edge of the typical "duck curve". If it gets popular enough to affect the grid, it might get the solar-induced demand slump larger, but make the edges even sharper.
Would that make grid scale battery storage with its instant response even more important?
Solar panel installation costs, at least in the US haven't dropped in 15 years. It's still $25-30k to install 4kW-6kW worth of solar panels.
That's why I installed my 13kw system myself. I saved a ton of money, assuming you don't equate time with money, otherwise it will have cost me a fortune. It was a great learning experience, and quite fun.
That’s absolutely insane. I just had 5400Wp of panels installed with 15kWh of battery storage and it was ~€12k total. The battery was a bit over half of the costs. That’s the total cost, hardware and labour.
No need for permits for rooftop solar and the only dealings I had with the energy company was filling out an online form to register it. Took maybe 2 minutes.
3 replies →
The US is getting fleeced! 8 years ago it cost me about $10k AUD to install 6kW. Yes, it came with a $2.8k subsidy but still we are talking about a third.. 8 years ago.. And I paid extra for a Fronius inverter.
1 reply →
Your numbers are way too high. I live in the very expensive San Francisco Bay Area and my system 6kW before federal tax credits was 16k to install in 2021. After credits it was < $12k. I have a friend in Tucson AZ who just paid $12K for a 4kW system with no subsidies.
I did not add a battery because at the time it would have doubled the price. Also, because I have net metering the battery never pays itself off.
2 replies →
US installation costs seem insanely inflated compared to the rest of the world.
Rooftop solar generally requires professional installation. Balcony solar, as discussed in the article, does not require professional installation and simply plugs directly into an outlet.
2 replies →
Dominated by labor costs, right? It'll probably just keep going up at this point, even if the panel cost went to zero.
8 replies →
> It's still $25-30k to install 4kW-6kW worth of solar panels.
You mean "to have installed".
I installed 6.7kW for $12k, but did all the work myself (with a permit).
That’s wild. I’m getting 12x 450kW panels (5.4kW) and a 10kWh battery installed on my roof this month for a grand total of like €7k.
That’s the total cost including all materials and labour from scratch to a fully functioning system.
My Dad is getting 10kW of panels and an inverter installed tomorrow. Fully installed and permitted for $5k AUD.
I got 7.6kW fully installed with inverter for $8k CAD a few years ago.
We paid $17k ($12k after subsidies) to install 5kW in Arizona five years ago.
I've always wondered if its possible to just buy and install the panels yourself.
4 replies →
With the plugin solar I can imagine people in single family residential installing them on both sides of fences and gates to get an around the day benefit.
Also, with the price of solar panels decreasing below most (wood?) building materials with way higher durability, no paint required, why wouldn't it replace most sun facing siding applications aside from being "ugly".
There is a special place in hell reserved for the Karens who call PV panels ugly.
> it gets popular enough to affect the grid,
The plug in solar systems are small and usually mounted in ways that don’t capture as much energy as the same panels mounted on a roof. These systems aren’t going to get popular enough to make a big difference in anything.
I think it’s nice that they’re available for people to do some small scale offsets, but I think they’re more of a gateway to better solar installations. They also send people down the path of investigating battery storage add-ons, which might actually be a better long term solution for everyone.
If we can get to a point where we can buy plug-in batteries that are subsidized by requiring coordination with the grid, the power companies could get distributed, controlled battery storage to work with their demand curves. This can already happen with the bigger permanent install batteries.
This may be a stupid question, but I've always heard to never plug a generator into an outlet - what makes these safe enough that you can?
The biggest problem with plugging a generator into an outlet is you need a double ended cord. If you use everything correctly they work fine, but there are too many ways things can go wrong. The most obvious one is you plug everything in, start the generator, and the trip over the cord on you way back inside, thus sending the live male end flying toward you. Once in a while a kid will see these dual male plugs and plug them in - lots of ways things can go wrong here.
There is also the problem of backfeeding, but this is more theoretical - even if you know to limit your power use, your neighbors won't and so your generator will trip its own breaker. Linemen are taught to either treat power lines like they are live, or to short them to ground - it can happen they don't do this and you kill a linemen, but still not as big a worry as it is made out.
They make generator "inlets" that sidestep all these problems when used correctly. Most common I've seen is a block so you can't have the inlet and the main breaker both on at once.
> There is also the problem of backfeeding, but this is more theoretical
it is not theoretical from the POV of power company employees working on their lines. the power goes out, they go to fix the equipment or wiring, and if the inverters connected to the grid have not shutdown, there could be 10s of kW to even MWs being backfed into the system they are working on.
that's why in the US at least, grid-tied inverters are required to have protection against this. if they do not see power from the grid, they shutdown (and rather quickly).
The inverter box contains circuitry that cuts power output within some specified number of milliseconds if unplugged rendering the prongs "cold".
It's not so much being unplugged as it is sensing whether the mains power is down. If it is, they stop backfeeding immediately, just like hardwired solar inverters do.
If this weren't done, there would be risk of electricution to anyone working on wiring in the house or on the utility distribution network.
4 replies →
And the panels synchronize to the grid's frequency; a generator doesn't have any logic to synchronize to the grid's frequency.
Skip to about 10 minutes into this video: https://practical.engineering/blog/2022/12/5/what-is-a-black...
Furthermore, the danger of backfeeding is if you do it in a power outage and you start to power your neighbors' houses. It'll overload your generator and create a hazardous situation for anyone working on the wires. (This is why you're supposed to install either a generator switch or interlock. I have one that only allows me to energize when my main breaker is turned off.)
But how do they do it technically? Some countries require anti-islanding devices for grid connected solar, these are around $1000. That alone is much more expensive than the $300 plug in panels.
Thanks. I would have asked Claude or something but I know so little about this topic that I wouldn't have been skeptical enough of its answer.
Fancy power electronics in them that make sure they only send power to the outlet while the grid is energizing it too.
In addition to the electronics that others mentioned, they also have limited amperage. That way even if you are pulling from your mains power and the solar at the same time, your circuit hardware shouldn't melt or catch fire.
Unless you have five of them. Which people will absolutely foolishly do.
These sync with the grid and also have safety mechanisms to avoid backfeeding if the grid is down (or it's unplugged).
How do these work when plugged in to only one of the split phases on a US-style 120 system? Because I'm a nerd, I know which legs of the phase go to which outlet in my house, but I don't expect everyone to pay attention to that. I assume something has to take that into account somewhere.
There is no problem and so nothing needs to account for it. A split phase is just a transformer with three windings, and one is connected to the other. We call one side (high voltage) the primary, and the other two secondary, but the transformer doesn't care at all, it can send power either way (there are limits but we are well under the maximum rating of the transformer so we can ignore them). If you only draw 240 volts then the two connected windings act as a single secondary, if you only draw 120 then one of the two secondaries provides power. Any other combination - the transformer doesn't care.
U.S. homes typically get power through two hot wires. The hot wires are connected to a utility company's transformer and are 180 degree out of phase. Each supplies 120 volts.
The power from the plug-in outlet is consumed by any devices connected on the same circuit first. Any extra flow through the electric panel’s bar connecting the circuits on the same 120V phase, where the devices on them use the extra next. Any excessive power flows back out of the meter on the 120V phase line on your service connection to the transformer at the street block. The transformer might feed it to your neighbors. In any case the transformer feed electricity to the other 120V phase line back into your service connection, the meter, the panel, the other split phase bar, the circuits on it, and the outlets on them. The devices on the other split phase circuits technically are not using the plug-in power directly.
Most modern meters measure electricity going in and out on both split phase lines as a whole, as a net amount, so the electricity consumed in the other split phase circuits is offset by the plug-in power. However some old meters add the outgoing electricity up as consumption so you are paying for the electricity fed into the grid. Call your utility company to make sure.
Also, unless you have a net metering agreement with your utility company, you won’t get paid for any excessive electricity fed back into the grid.
I doubt it matters. The power company also theoretically has to deal with houses where they coincidentally draw more from one side of the split than the other. But I suspect it all averages out, and the contribution of a couple plug-in panels in a bunch of houses won't change anything.
It backfeeds onto the grid and becomes the utility companies problem to deal with. This is similar to them dealing with a house that is an unbalanced consumer between the legs.
To my understanding, it is basically a non-issue at residential voltages. To be a problem it would require all the houses on a transformer (there are typically just a few for each transformer) to be unbalanced significantly in the same direction. That would be the end of it, too, because the 240V split only happens at the transformer.
My concern is what happens to grid stability as we replace synchronous generators, with their enormous rotational inertia, with thousands of grid-following inverters. They can all phase-lock to 60 Hz, but without enough inertia, what keeps that frequency stable during sudden changes in load or generation?
grid forming inverters : )
I don’t see many (any?) plants using them, is the technology there yet? Genuinely curious.
And on an unrelated note, it seems that hybrid power plants are becoming a talking point now and they seem to make a lot of sense. Like covering dams with solar panels saves on water, make PVs cooler/work more efficiently and you don’t need to worry about permits/building more grid connections because you can simply slow down hydro during daytime (and get along with grid following inverters just fine).
2 replies →
[dead]
I hope the next step for this is plug-in battery storage. All the on-grid battery hybrid inverters I can find in the USA are either single leg 120V or 12kW for $5k. I just want like 3kW dual-leg with support for a dozen kWh of batteries
I've seen setups where they put a 48v battery between the solar panels and plug-in micro inverter. No idea how this impacts efficiency or if there's any safety concerns though.
Yeah it seems like the inverter manufacturers don't see demand for that. I was thinking maybe the Victron Multiplus-II 2x120 could be paired for 240V output but I was wrong, that's only on grid power, it won't make 240V from battery.
Obviously the inverters and pairing technology exist, but I don't know where to buy one retail.
Victron devices on sale in Europe/UK all do 240V output. I've seen someone do a boat build in the USA with Victron hardware that included 240V circuits (because the builder was a UK/US person, and they wanted both 120 and 240 "normal" circuits).
1 reply →
The Bluetti Apex 300 is an expandable 2.7kWh 3.8kW dual-leg battery + inverter + solar generator for ~$1000 (on sale).
The EG4 12kPV does 8kw split phase output and is $3k, but haven't seen anything smaller than that yet.
Does this seem like a bad idea from a safety perspective?
With fixed solar installs you're likely to find some kind of switch or labeled breaker to disconnect. The system is designed with a central "power in" that's (hopefully) obvious/proximate when you're standing in the breaker room.
These things could be injecting power anywhere, so you need to know they're there (which may be less apparent than roof/field panels) and go around and pull the plug(s). Relevant to electricians, firefighters, etc.
Yes, there are serious safety concerns. Both islanding, which is where a circuit is hot when it shouldn't be, and from a circuit overload.
Your circuit breaker protects your circuits by putting all the load (eg your microwave) on one side, and your supply (mains power) on the other. If too much load is present, the circuit breaker trips.
However, plugin solar puts invisible supply on the load side, which your circuit breaker cannot see. Let's make an absurd example so you can see what the problem is, then scale it back.
Imagine someone buys 5 panels that can each supply 5amps. They plug them into outlets on a 40 amp circuit. They then proceed to run their toaster, microwave, vacuum, and hair dryer. They can draw 65 amps through the wires before the circuit breaker trips. (40 from mains, 25 from the panels)
Let's say they had a good electrician who installed 6AWG wiring on that circuit, which is rated for 50 amps. The circuit breaker used to trip at 40, so no problem. But now up to 65 can go across the wires and suddenly you are exceeding rating for wires.
Now you might say, "most of these are 3.5 watts, and they clearly say don't use more than one". But I say that's a "good intentions solution". We should make it mechanically impossible to do the wrong thing. Maybe these panels could try to communicate over the electrical wires, and if they detect a signal from another panel they should self limit. Maybe we need to rethink circuit panel design. But as it stands people will absolutely buy one of these, decide they love it, and then buy 4 more.
Plug in solar inverters turn off when they detect a loss of grid power. Anti-islanding is a requirement for them to be certified.
These rely on seeing a grid frequency to follow when they output power. If you shut off the breaker for the circuit they're on, no grid frequency to follow, and they shut off their output. When unplugged, the plug never has any voltage on it.
These systems monitor for a loss of grid power and turn off when they detect an outage. UL 3700 is the standard, if you want to read more about it.
I wonder if they’re set up to cut off if the outlet has no power for exactly that reason.
They’d also probably depend on a power signal to frequency match.
Perhaps also useful would be plug in batteries, especially if one has variable rates. Charge when cheap, discharge when expensive.
One constraint on these I've read is that if you have sources and sinks on the same circuit, you might overload the line without tripping the breaker at the box. If I'm understanding this correctly this has caused them to limit the power of plug-in solar to a fraction of what a single circuit could potentially carry.
Yes, it's designed so that total current and potential heat problems are still within safety margins of circuits built according to code. In most of Europe, one regular (or upper end of regular, depending on country) residential circuit can supply 3.6 kW (230 V * 16 A = 3680 W), so 800 W are "just" a 20% overload.
https://archive.today/NEPz3
If lightning strikes does the risk of fire increase with solar ac ?
https://wallhop.io/https://www.nationalgeographic.com/enviro...
This is fun, but utility-scale solar is far cheaper.
It doesn't have to be cheaper than utility-scale. It only has to be cheaper than retail electricity.
In other words, it can be useful even if it's not the most efficient way to do it. It only has to be more efficient than the status quo.
I don't have thd capital to build utility-scale solar. I do have the capital to install residential solar. My electricity is now cheaper.
There are advantages to distributed infrastructure as well! You mentioned one of the biggest disadvantages.
I am thinking along the line of:
Utility solar is also distributed if there is enough of it installed to matter for discussion. A single installation is such a tiny share of the electric load that we can ignore if for all reasons you care about distributed. (or care about solar for that matter - it is a drop in the ocean for the environment)
Utility-scale solar might be cheaper but doesn't make my house resilient to grid failures. It also only benefits me when the grid is upgraded enough that ... well, it benefits me.
Plug in solar doesn't make your house resilient to grid failures either. You would need an inverter that can generate an AC output without having an existing one to follow; a disconnect to isolate you from the grid during an outage, batteries to smooth the output, an electrician to install it, and an inspection to certify that it was all done correctly.
If you are going through all of that, there is not much benefit to plug-in solar instead of traditional.
4 replies →
These panels do not work without the grid.
8 replies →
I'm sure it's cheaper to somebody. But with home solar, I can actually cut my power bill by a noticeable fraction.
It is easier to find a million people with a few hundred euros and a sunny balcony than finding one dude with a few hundred million euros and land on which building a solar farm is permitted.
Problem is for most of USA utility scale = utility profit for share holders.
For example Duke is for profit here in Florida, and charges about 25% more per KWH than OUC that is a public utility.
This leads to pricing where on one street your power bill is $250, but one street over its $200, often coming from the exact same power plant.
Duke is just excessively expensive.
FPL is also for profit, and is cheaper than OUC.
1st 1000kwh with FPL are $0.11461/kwh Above that is $0.13461/kwh with a base customer charge of $10.52
1st 1000kwh with OUC are $0.1155/kwh Above that is $0.1405 with a base customer charge of $18.50/mo
Total cost with FPL for 1000kwh for the month before state and local tax is $125.13
With OUC it would be $134.
https://www.ouc.com/wp-content/uploads/2025/09/2025_10-OUC-E...
https://www.fpl.com/content/dam/fplgp/us/en/rates/pdf/reside...
The biggest factor Id say is FPL has significant amounts of solar and nuclear generation.
https://www.fpl.com/content/dam/fplgp/us/en/news/2025/fpl-ne...
18.8% Nuclear and 8.4% solar (more than double the national average!)
OUC on the other hand has less than 3% Nuclear (generated / purchased from FPLs plant on Hutchinson Islans!) and <6% solar, with a massive 24% still being generated by coal! (FPL demolished their last coal plant ~8 years ago in Indiantown, I watched it live!)
https://www.floridapsc.com/pscfiles/website-files/PDF/Utilit...
So while FPL is technically for profit and OUC is not... FPL is cheaper and greener than OUC.
I say this as a long time Florida resident who remembers when FPL truly sucked in many ways. They’ve, demonstrably, put in effort to make electricity greener and cheaper here in FL. (Even with all of their efforts against home solar).
Last I checked the biggest cost in the electric bill is transmission, by a wide margin. Home generated power however small helps everyone.
Isn’t it backwards? If everyone had a little bit of home generated power, then the actual energy part of the bill becomes smaller, and the cost of transmission becomes an even greater fraction of the total cost.
And since transmission cost is typically bundled with the energy cost, it means the final retail energy price has to go up to cover the transmission cost.
2 replies →
Where I live we have Time of Day electricity pricing where the prices jump 2-3x during high demand. Panels conveniently produce the most power around this time, so this can save people money.
It's not and it will NEVER be.
Utility companies are not incentivized to lower prices because it means less money for them. Do you remember when power companies told people to conserve power and then people successfully did this? And then they raised rates because they weren't making enough money? This happens in California ALL THE TIME. I've lived here 30 years in Silicon Valley and it's the biggest scam that no one talks about. It happens with electricity and water. With water its even more egregious because they told us to conserve water because of the "drought" but once the drought was over, they raised rates because people weren't using enough water. My connection fee to water is over $100/month without spending a drop of water. That's why I stopped conserving water and water my lawn every single day because it turns out that my water costs are only about 1/3 of the actual water bill costs so fuck it!
It's the same playbook over and over again, there's no incentive to lower rates at all because it's an easy way to make money over an entire population of tens of millions of people.
Now PG&E is fighting to charge solar panel owners $100+/month just for the privilege of being connected to the grid. That would make having solar panels even more expensive than not having solar panels which is utter hypocrisy but no one seems to care or point this out. It's a complete and utter scam.
EDIT: I forgot to mention last year the rates were $0.37-0.45 per kWh, until this year when they implemented a base fee of $25/month, so they lowered it to $0.33-0.45/kWh. Rates in Nevada are 1/4 of that.
2015: $0.17-0.33 per kWh
2020: $0.24-0.38 per kWh
so prices have more than doubled in 10 years. Fucking criminals.
I live in Florida, and I'm building a water battery, so I can freeze it at night when electricity rates are cheap, and use it to cool the house during the day.
The day after the system goes live, they'll probably announce flat rates for any time of day, just to f' with me. :(
2 replies →
We should build now in anticipation of drone warfare. Utility-scale solar is easier to take out. Same as natural disasters.
The more stable you think the future will be, the more you want to capture the efficiency of central power.
By that logic literally everything should be distributed. That's going to be a big undertaking to re-architect our entire civilian infrastructure against that.
I'm not saying you're necessarily wrong, I just don't see society taking that measure until it's either 1) cheaper, or 2) the threat moves from being just a threat to reality.
5 replies →