Solar panels that plug into your wall
nationalgeographic.com
nationalgeographic.com
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?
Matt Ferrell just did a video on this recently https://www.youtube.com/watch?v=R3eEzdpi12I
The UK variant seems to have more traditional failure modes of "excessive charges for maintenance of communal areas": https://parliamentnews.co.uk/tales-of-intimidation-excessive... , but people are still capable of having the occasional fistfight or protracted legal dispute about the wrong kind of hedge in a more informal, adhoc way.
Just lookout for tornadoes.
This setup would cost north of $50k (possibly north of $75k, depending) if installed by contractors. Labor costs are extremely high here, since COL is extremely high.
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.
From where did you source the equipment?
400V TN 3P grid with export where I am paid spot. Had to fill in a form online that got approved automatically. The energy company (separate from the grid company) automatically detected my export and started deducing the sales of solar from the bill.
The installer had to confirm the installation to the Enova government entity to release my €3k subsidy though.
I just contacted a well-reviewed solar installer and they took care of everything.
My family got an fixed three phase setup with a 12kWp, 8 kWh battery (BYD) and a Hybrid Inverter (SMA) alongside a Level 2 22 kW EV charger for a grand total of 16.000€.
My plugin solar setup was a DIY with 1kWp of panels + an 800W inverter and did cost a total of 350€, including the mounting hardware.
I do wonder if having an electrician come by after the fact to inspect it counts as "supervising", though.
The exam is much harder than one might expect, but if you're reasonably competent with residential wiring, far from impossible. It covers a bunch of stuff that is irrelevant for 90% of all residental solar installs, naturally.
That’s the total cost including all materials and labour from scratch to a fully functioning system.
We (northern part of Germany) installed 7 KW panels with 10 KW battery for €15K in 2024. My neighbor is installing 10 KW panels with 10 KW battery for €18K this week. So it seems the total costs have not dropped any further in the last 2 years.
If you don't have utility approval to connect, you won't get net metering benefits, although you could offset active use (and if you had battery storage, I guess you could make it work). At least my meter doesn't run backwards, it has a count for energy in and a count for energy out. If we didn't have utility approval and had significant energy out, I'm guessing there would be questions. We have a fairly generous tarrif, and our system doesn't make sense without utility approval --- we generate on one meter and use on another meter and rely on meter aggrigation for the generation and use to offset, and they will offset 1 for 1, once the account gets fully set up.
Our utility is still offering 1 for 1 net metering for new installs (accumulated credit expires at the end of March every year) and have not proposed a new rate schedule. They say that existing connected systems will be able to remain on the current schedule indefinitely. That's the best I can do for the future at this point.
If it does change for us in a negative way, I'll have to bite the bullet and buy an electric car and charge when the sun is up. :P Hopefully negative changes happen later rather than sooner.
Permitting was new for me and it was tough to navigate alone, but definitely possible.
Homeowners are getting the short end, but the solar installers are doing well.
Here's a long podcast episode talking about why it's so much more expensive in the US versus Australia, with a solar expert from Australia that had just added a bunch of C&I solar here in the US:
https://www.volts.wtf/p/whats-the-real-story-with-australian
Local permitting, utility fuckery, tariffs, etc. all add up.
The far lower costs in Australia are not due to executive pay, it's due to basic efficiency. Americans are doing things in horrendously wasteful ways, because the system is set to act that way, and changing our system of government is too difficult due to political infighting. One of many examples in the article:
> These things are highly optimized that companies will try to do the scheduling so they’re doing two or three jobs on the same street or in the same suburb on the same day, so they don’t have to drive across town to do the second job. If there’s a delay of a couple of days, it’s because they’re trying to make sure that they’re going to do your neighbors at the same time they’re going to do yours. The thing that costs you money in contracting is what they call truck rolls. I believe in the US there’s something like five or six truck rolls per solar installation. In Australia, it’s as few as one or two.
See also the US healthcare system. Or residential building.
What system exactly. Offices ?
> See also the US healthcare system.
The US healthcare is full of suits getting commissions and powerpoints.
> Or residential building.
Again suits and commissions.
At least you bought them 8 years ago and not 20, you could have had a 1.5kW system for the same price.
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.
(My installer ended up flaking on me, and then I gave up because NEM 3.0 was coming too soon to find a fallback.)
You mean "to have installed".
I installed 6.7kW for $12k, but did all the work myself (with a permit).
I got 7.6kW fully installed with inverter for $8k CAD a few years ago.
Free refills on soft drinks are generally still a thing in the U.S.
> I'm in Europe
Wait until you hear about American Insulin.
At that date I got into the feed-in-tariff scheme, and it has long since paid for itself just in cheques mailed to me by the utility.
$30k is mad.
For the price you’re talking about, you could also get a system with 15 kW of panels with a good 20-30 kWh of battery storage too!
It's the regulation cost that's really hurting us.
Just the required paperwork for the permit in my region cost ~2.5k. structural engineer was 800, architecture diagram was 800, certified electrician stamp on the plans was 800.
Add in the extra cost to facilitate RSD (~5k after mlpe devices, and extra wiring) and tack on the cost for utility interconnection agreements.
Then deal with the NEC requiring UL listed items with no/very little cross certification with things like CE which effectively means you can't buy equipment from China, at least not without a US shop taking a huge markup for branding/certs.
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Overall, it's just a mess. I walked away from the project (completed, all approved) with a huge dose of skepticism for the permitting/certification/approval process.
11.2kw in panels, ~12kwh lfp battery, split phase 240v install - ~28k usd.
Of which ~10k was regulation driven, and doesn't change much by install size.
"Balcony solar" (<800W) with absolutely zero paperwork (edit: I'm wrong, still needs G99) has just arrived to the UK.
The specific exclusion of batteries too is a sop to the industry. It’s a step forward, but needs to go further.
Currently in the U.K. they have to have U.K. appeal not just standard eu approval. Hopefully this will be fixed by next year and prices will Be more reasonable.
Hopefully too regulators will Change to allow battery Storage as long as it’s not pore than 800W inverter.
Personally, I'd love to see the United States, and the rest of the world, decrease its reliance on oil. We won't get off it in any of our lifetimes, but we should move in that direction. I like diversifying. Any bit helps. Solar in Australia and Arizona. Maybe less so in northern Maine. Wind turbines where there's wind. I personally don't have any aesthetic objection to them. I think they look kind of cool. And certainly better than smokestacks. And so on.
Current lowest costs from national retailers that I've found (been looking today as it happens!) is City Plumbing - £336 for 475w, £480 for 1050w (panels with 800w max inverter).
I've been doing some advocacy work related to balcony solar mostly from a conceptual standpoint but am a renter and don't know much about the actual costs and process behind installing roof panels. I'm curious to know whether there are any low-hanging fruit we could organize around to reduce the regulatory burden on the consumer.
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.
They already are in a few countries.
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 inverters follow the grid AC and shut off their output if they are disconnected or unplugged, so the plug is never "hot". The power they input into your home wiring/the power grid is limited to 800 Watts as to not overload any installation. And the power meters know not to run backwards if you happen to feed power into the grid. Most can even meter how much power you fed in total (you're not going to get paid for it, though)
If you want, you can add battery storage that follows the same rules but lets you save excess power during the day to feed into your home at night or during demand spikes (washing machine, ...).
The setups are dirt cheap (often 200 - 300 EUR for an inverter and 800 - 1000 W(peak) of solar panels) and pay for themselves in about 1-3 years in saved electricity costs.
If you want to get an overview of the ecosystem, googling "Balkonkraftwerk" gives you the most relevant results.
I passed high school physics with good grades, so … I’m not surprised other people instinctively say this can’t possibly be a good idea.
What's new is cheap and ubiquitous micro-inverters. Before it wasn't worth putting a $800 inverter on a small 2-panel 600 or 800 installation. Now with micro inverters being so cheap, this tech becomes viable. And with loads so limited (less than a microwave) the regulation is equally light to allow this convenient plug-in solution.
But it’s AC, the electrons are shuffling in both directions at 50/60hz
Voltage goes forwards and backwards and odd but current also goes forwards and backwards, for both appliances and generators.
The difference between consumer and producer is only the phase angle between the voltage and current waveform.
Because power is VxA, do that across the wave cycle and the power direction changes for consumers and producers.
At every junction, Kirchhoff’s current law will sum the currents so you get a “net current” waveform on a wire that might have both a kettle and a plug in solar panel.
That summation means the kettle will chomp as much current as the panel can deliver and than take more from the grid. Swap the kettle for a small LED which takes a fraction of the current and the sum gives a NET supply, and on to the next junction.
It took me a while to get my head round it too.
Take power out of the flywheel? Sure, why not -- that's exactly what we've done with it at home since we had an AC grid to speak of.
Try to impart higher voltage to put power back into the system? Fine, no worries. Flywheel just accepts and absorbs whatever you put into it as long as it has the right shape.
Try to change the flywheel's AC frequency or waveform, though? Hah, fat chance: Flywheel will trip your breakers or reduce your gear to ash -- whichever comes first. We play by the flywheel's rules, and those rules aren't optional at all. It may be just a big dumb flywheel, but the flywheel's enforcement is absolute.
Anyway, it's a big mythical flywheel. We get charged money to take power out of it, and (with the right arrangements) we get paid money to put power into it.
And by design, grid-tied inverters are quite good at following the flywheel's rules. They match the flywheel's waveform very well [lest they go poof]. They can only put power into that flywheel, and they reject power from that flywheel. The inverter is a one-way thing that, from a high-enough viewpoint, looks kind of like a check valve or a diode does.
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But it's not an ideal, perfect system. It does not exist in a world of frictionless pulleys and ropes that don't stretch.
That imperfection shows up in the wires and transformers connecting the house to that flywheel system, in that these parts have a non-zero impedance. (For the sake of this discussion, impedance can mean about the same thing as resistance)
And that impedance is useful. It means that we can increase voltage a very tiny bit on our local leg, and thereby succeed at using our puny little solar power system to help cover our own local base load.
Suppose our plug-in solar widget can produce 800 Watts today. The plug-in kit increases the voltage that it drives that plug with until 800 Watts of power output is achieved (which is only a very tiny amount of extra voltage, but it's real anyway). This is its purpose: Where some robots pass butter, this robot puts 800 Watts into a power socket.
Since the wiring between the plug-in solar and the local household baseload stuff has a lower impedance than the path to the mythical flywheel does, our baseload stuff (the fridge, the router, the fan by the window) gets first dibs at that 800 Watts of minutely-enhanced voltage.
If we produce more than we use, the excess local power production gets provided to and soaked up by the flywheel (maybe we get paid for that).
If we use more than we produce, then the deficit is made up for by the flywheel (and we definitely pay for it).
If our generation and consumption is perfectly balanced (which never really happens), then the flywheel plays no real part in the program except to provide a waveform for our solar inverter to synchronize with.
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Anyway, it's not new tech at all. It's safe in that it won't work at all without a connection to the big flywheel in the sky. And folks have been using grid-tied inverters for quite a long time, but that was done on a dedicated circuit (with a dedicated breaker or fuse or RCBO or whatever they're called wherever you are).
But there's still some new stuff going on: It can be a plug-in system that works without individual planning or permitting; in some places, a person can legally buy and use a kit without obtaining extra permission.
The safety of sharing a circuit is also important, since enhanced potential exists for overheating things. Germany limits their plug-in solar to 800 Watts, or about 3.5A @ 230V, while their circuits are usually 16A.
That means there could be as much as 19.5A of nominal current flow within a circuit before some combination of circuit breaker or inverter limit is reached.
I learned a long time ago to never question a German about their electrical standards, though, so I can only assume that very smart people have worked very long hours to see that this situation is safe-enough.
Current load pulls the voltage down, sourcing current pushes it up. No bother, as long as your sources cut out if the voltage goes too high, and your loads cut out if it goes too low.
In terms of electricity and physics, this is unremarkable, the bit that probably scares people is the fact that you have a plug connected to something that's _outputting_ AC, particularly for those of us with 240V supplies.
If it were any old AC source on the other end they'd be correct, but current technology allows the output to be cut in milliseconds, faster than the period of a single AC wave, once the plug is removed.
Tangentially; if you have solar (mine's roof-mounted) don't assume that flipping the breaker means there's no power; I live in a 1930s UK home with all sorts of interesting wiring and flipped the breaker to change a plug socket, only to be shocked; literally and figuratively when it was hot.
When we had our solar installed, we had to make sure we had a newer power meter that could handle power both ways, so it probably is a problem for some situations, but the power flow for a single solar panel into a plug isn't enough to trip this, or maybe newer power meters are better?
We definitely think of it as somewhere a power comes out of, but I don't think it's the name, just that it's only ever been that way.
Clearly some people think of it differently if they're plugging generators into wall sockets to power the whole house, dumb as that may be.
My home is 1930s, it's fuse, in the black Bakelite housing typical of the era was insufficient and we were missing a incoming breaker to/from grid, those were updated. Our meter is much more recent, though still dated; allegedly it would have worked but it wasn't a smart meter, which we wanted so we had that updated.
I've also heard through my many hours of watching Solar videos on YT before our install that some breakers, RCDs(?), RCBOs(?), whichever it is, aren't always suitable for bidirectional current flow, so that's a possible issue too.
All of that is aside the "suicide cord" danger of the old generator method, but that's gone now with modern tech, the output is cut before you can get your hands on the contacts on the end of a plug.
It's just been legalised here in the UK, and I think it will help people with their bills, but the key is to keep installation costs down; if it's DIY you can look at a decent ROI time, but with the cost of trades-people these days, if you have to call out a sparky to inspect before you plug it in, you've added potentially years to your payback period.
At ~800W, I think on the whole we'll be fine; the equipment in our homes has got much more efficient over the years, and our homes were mostly built for times where we were using higher powered devices. If you can draw over a kW to power an electric heater or kettle, I don't see why feeding a mere 800W back in would be a huge risk.
Disclaimer: I'm not an Electrician, but I do have a degree in Electronic Engineering.
The solar is the same way, but with an auto cutoff.
Yes, but that's dangerous for reasons[1] that people often don't bother explaining -- and that aren't important for solar grid-tied inverters[2].
[1]: The seemingly-ideal way to plug a big fat generator into an American house in a hurry is to use a double-ended suicide cord to feed into the 240v dryer outlet. That provides plenty of power to get a lot of things done, it's a single-outlet circuit, and it lights up both sides of the split phase panel. But that's bad.
The most obvious way that it's bad is because we shouldn't have energized male prongs. Like, ever -- that's just extra shit to get hurt with. But this suicide cord idea relies upon their use.
The other way that it's bad is that the generator doesn't know whether the house is still connected to the grid or not. So unless we deliberately disconnect from the grid, there's a wonderful chance that we feed it even though that grid is presently non-functional. This can fuck people up: The transformer on the pole outside (or in the box down the way, or whatever) will cheerfully convert the sleepy 240v from the generator into thousands of volts on the wires outside that were completely dead until someone decided to get clever. Now, the guy cleaning up storm debris down the block or the lineman doing the repair gets the fuck shocked out of them in spooky-dead kinds of ways. (Yeah, yeah: We shouldn't ever do anything near downed lines of any kind, and the lineman should always have appropriate PPE. And we shouldn't plug our generators into our dryer socket, too. Death is permanent.)
Panels with interlocks and wall-mounted male sockets that accept generator input both exist, and the combination of them mitigates both issues. The combination also prevents a third problem: Power coming back on while the generator is running.
[2]: But a proper UL-listed plug-in solar inverter doesn't have any of these problems. The issues are sidestepped because it outputs nothing when the grid is down, as a baked-in function. So there's no energized male plug to be a hazard, and there's also no interlock required to ensure that the grid isn't backfed while it is down. You can hypothetically unplug the solar inverter from the wall on a bright sunny day and lick the prongs, and nothing happens.
This has very little to do with the power meter itself, and more that the power company wants to be able to monitor if the meter is 'running backwards' (i.e., if power is flowing out rather than into the meter). Older meters could only run in one direction.
> Clearly some people think of it differently if they're plugging generators into wall sockets to power the whole house, dumb as that may be.
There's frankly nothing wrong with this if you do it properly. The 'proper' way would be to have a generator input socket near the main breaker panel, and the main breaker is interlocked with the generator input (i.e., only one can be on at a time). You absolutely can just plug a regular generator into a wall, assuming you aren't overloading the wiring or breakers... the safety issue is overblown. The reason why it's 'super dangerous and bad stuff will happen' is because people are stupid and forget to turn off the main breaker. Which, admittedly, is a reasonable concern because... people do forget.
On an AC circuit, all connections are duplex.
It needs to be paired with a transfer switch or it will backfeed.
Unfortunately it is a far too common thing for people to rig these things up themselves leading to all sorts of funny complications.
i.e You have a circuit with max current 16A; clever end-user plugs in 3 x 800W panels into different sockets BUT they are unfortunately on the same circuit; now 26A can be potentially drawn through a single cable IN THE WALL without tripping the breaker. This is a BIG fire hazard.
And you can't wave this away with instructions. It has to be 100% impossible for an end-user to do this.
Seems like the worst case scenario is when you mix solar panels with load on the same circuit.
800W at 110v is about 7 amps. Suppose you have a 7 amp solar inverter plugged in as the first thing on that circuit. Further down the line, you have 22 amps worth of load. The circuit breaker sees 15 amps, but the wiring between the panel and the load is carrying 22 amps, which would ordinarily trip the breaker but it doesn't because the solar setup is masking it.
I'm not an electrician. Perhaps wiring code has enough safety margin that being 800 watts over on some circuit isn't actually a serious safety concern, but I could understand why this might not be allowed.
The EU is on 230v, so maybe it's a bit more practical over there because you can add twice the solar capacity for the same amount of additional current you'd have in the US, so they aren't eating into the safety margin quite as much. Though it seems they also use thinner wire gauge generally, so maybe the difference is moot.
Don't get me wrong, I think they're a spectacular idea, especially for renters. But you'd need an electrician to check the circuit and maybe even have a special balcony-solar-plug to prevent people plugging in too many panels in the wrong locations.
Quick edit: Random idea. I guess if the panel could communicate with the RCBO it's connected to and that RCBO can dynamically alter it's trip current could also solve it. But again, that's an electrician call and new thing installed.
Of course your argument still stands, but we're talking about at most 3.5 A extra current, not 10 A. Home installations seem to be adequately sized to be able to handle that load. At least I'm not aware of any reported incidents, and people have been putting them up for quite a few years already. And typically, German regulations err on the side of caution.
But sure, with 110 V, you will have more problems with the extra current for the same power, so in the American grid there could be further precautions necessary.
We're also very litigious, as it isn't hard to convince a jury to award damages to a fellow moron.
Not everything, Americans do get by with doing other moronic things that other countries do things to prevent. However other countries also do their own moronic things that Americans are much less likely to.
https://members.modernvespa.net/brian_herwick_-_coolass/uplo...
Not picking on the US though. These panels in their current incarnation, are lowering the level of safety of electrical everywhere.
This is all just my opinion though. A lot of my background is in compliance. I've been frustrated by some obvious electrical safety advancements that are STILL not being implemented. I also have first hand experience with many many signed off electrical systems which were death traps. This all biases me heavily towards not compromising on electrical safety. But maybe I am overreacting.
To use your car analogy, we're not banning vehicles. We're disable one of the airbags when enabling fuel economy mode.
> you can't wave this away with instructions
But apparently you can with legislation about instructions.
Edit: government safety investigation https://assets.publishing.service.gov.uk/media/6a32bfea0bea2...
Final edit: "61% of respondents support having one device per household circuit while 19% considered that only a single plug-in solar device should be permitted per premises citing alignment with 44 Engineering Recommendations G98 Issue 2 Amendment 1, impact on the network, old wiring in properties and the ability of consumers to correctly identify separate electrical circuits.
Government response: Having considered consultation responses and stakeholder feedback, the government's approach is to limit the deployment to one per power circuit, subject to corresponding changes to the G98. Some respondents suggested limiting the total capacity per dwelling to 800VA, but we think the evidence for doing this is weak considering most UK dwellings have a minimum of two power circuits"
-- i.e. they thought about it and the concerns got outvoted.
It's probably fine. There's a lot worse lurking in outdated UK installations. Then we get on to ring circuits, which the rest of the world disagrees with and also seem to be fine.
In the US, even with a warning, you'd get regular home fires as people hooked one of these panels into every available outlet just because they can. I wish I were joking.
I hope it's at least "probably fine". I've seen some pretty shoddy electrical work in my lifetime (including new installs) and am now of the mind that the deep-defense-in-depth of electrical safety we have these days is to also "cope" with shitty electrician work.
I think this will be your biggest practical issue in newer US construction. Arc fault circuit interrupters are now code for any wiring in living spaces. They can be quite sensitive to weird switching loads (and sources). I was forced to swap an AFCI for a normal breaker in my last home. The power supply in my workstation triggered the detection heuristic in the AFCI about once a day. I could cause an outage on demand by running certain workloads.
Obviously the inverters and pairing technology exist, but I don't know where to buy one retail.
welcome to the future
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.
It outputs at the same phase and frequency as the grid, and with a slightly higher voltage (think of a ball rolling down a slope from a higher voltage to lower voltage).
If the grid is down then it stops the inverter for a minimum safety period (some minutes iirc)
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.)
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.
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).
I realize this is a complete noob question but I'm still curious: with enough "backfeeders" could it not in theory be possible that the backeeders see each other's output and keep operating?
Say, a few houses at the end of the line, each with very little electricity consumption (no-one's at home), but with panels and inverters going full tilt, something like that?
(the specific case of very little consumption but panels and inverters going full tilt doesn't work as this would lead to the frequency rapidly increasing, exceeding inverter set points and the local grid collapsing with all the inverter tripping off. The danger scenario is closely matched load and generation, like a real grid)
Perhaps a more robust solution would be for the power company to install remote-switchable circuit breakers at various places of the grid. Use some sort of wireless IoT protocol to listen for "on/off" signals and to report back "I'm now on / I'm now off!". Then the power company can disconnect parts of the network by themselves, without trusting that every inverter, generator and battery will do the right thing.
Also, people have been back peeking the grid from their home generators for decades by now. Solar and inverters are a different variation of that attack, but it is nothing new. Any utility will have procedures because they can't guarantee that's not happening and we learned years ago.
I'm not saying it never happens, only that correct procedure already makes it not an issue
tl;dr Plug-in solar inverters must power off within a second if they stop detecting the grid's sine wave.
Generators have no such protection and will happily backfeed through the transformer outside your house to energize power lines. Line workers are careful, but there have been deaths. After hurricanes seems the most common based on a quick search.
So it's not a stupid question, indeed you should never plug a generator into an outlet. The double-ended "suicide cord" which allows you to do that has that name for a reason. (It can be fine to plug a generator into an inlet circuit, if the electrical panel has a proper interlock that physically forces disconnect from the utility before connecting the generator inlet.)
The better way (and legal way) to do this is to have a generator plug plug installed, this way when you switch over to generator your property is disconnected from the grid.
It can be quite safe to plug a generator into an outlet if you take precautions to properly island the system. I had an interlock on my breaker panel that would let me turn on a 50A backfeed breaker if my main breaker was switched off.
Solar inverters (esp for this use, but also in general) are grid following; they'll use the existing frequency and support it, and if the grid goes off they'll go off too and do no power-off backfeeding.
The inverters are thus broadly safer to be plugged in to systems that are otherwise unprepared.
Generators could be made grid-following (many are now inverter-based), but for most users that would be silly, since the supplemental power would be more expensive (and louder!) than from the grid.
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.
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.
My electricity supplier sends me a message nearly every week saying if I use less electricity during peak demand times then I get free power at weekends. https://octopus.energy/saving-sessions/
While the power doesn't go out often, it is a big deal when it happens and so a backup is useful. I'm still fixing the damage from the last one - the sump pumps not running for an hour in a rain storm is expensive. Fortunately it wasn't a long outage, much longer and the fridge/freezer would be a problem. In cold weather the furnace is important to keep running. There are other essential things as well that my house cannot survive without. Beyond that I want my computers to keep running if possible.
My sump pump hadn't run at all to my knowledge (I hear it so I think I'd know but maybe I was always gone or sleeping) for several years, but the power went out in a big rain storm and so the one time I needed it, it didn't run. (my old generator didn't kick on like it is supposed to, but I'm not sure if that circuit is wired to the generator anyway)
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).
ERCOT frequencies have sagged when the grid was stressed.
Decentral battery units in substations, similar to what Tesla did in Australia many years ago. They can absorb or provide reactive power as well.
The breakers do not prevent power flowing from an outlet back into the panel bus. They are thermal magnetic trip devices (99% of the time). The thermal is just a strip that when you get too much current for too long gets hot, expands, and trips the switch.
The magnetic part is a coil and too much current too quickly pulls it like a lever.
Nothing here will prevent “backflow” of electricity. It can’t because AC is always going both directions. It is reversing direction 50-60 times a second
The only thing you will hit is whether the power is on the same phase as your fridge. If not it’s going back to the grid.
well old NA circuits are notoriously shittier and lower-amp-rated than in europe lol
i don't think it's a good argument against balcony solar but neither is that a good rebuttal
Don't call the US system "shittier". It is different, but that doesn't mean better or worse. Anytime the US needs more a little more power we put in 20 amp circuits for the same wattage. Anytime we need a lot more power we put in 240 volt circuits. Different, but it works just fine.
And it's the way it should always have been.
Sure, there are concerns with possibly melting house wiring, but they require some vanishingly unlikely situations to occur.
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 monopolyIf you are going through all of that, there is not much benefit to plug-in solar instead of traditional.
So when the power goes out you unplug your fridge from the wall and plug it into the battery. In essence it operates like the standard camping battery/"solar generator", a la Jackery et al.
Having to plug in individual appliances seems to defeat the entire purpose. What happens if you’re away on holiday? Come home to a fridge full of trash? If power is back, do you even know how long the outage lasted? What about other devices that generally should have nonstop power or are typically hardwired? Sump pumps, HVAC equipment, water heaters, etc.
Where on the risk spectrum do you fall? I have a battery backup sump pump because I learned the hard way what happens when the power goes out and the generator doesn't start. If I fixed my generator though I'd have an automatic system that would run my sump pump, furnace, fridge, well, water heater, lights, computers, range, - and lots of other useful things as well so long as I'm careful about I run at the same time (anyone know how to fix a 1970s generator?)
The more stable you think the future will be, the more you want to capture the efficiency of central power.
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.
Completely agree. But I'm already there. Large scale economic disruption has just started. For that to remain peaceful over the next few decades would be a miracle. So we should plan for disruption, for which energy decentralization is a keystone, and the technology to make it practical is here.
California has a 600 MW Virtual Power Plant composed of Tesla Powerwall batteries in 85k homes. Central control of distributed generation removes a lot of inefficiencies. Household excess is available to the whole system.
There are probably only a handful of backbone transmission routes which serve tens of millions of people. These are isolated and unprotected and could likely be disabled with a loaded truck plowing into a critical piece of infrastructure.
It does not take much to bring down electricity distribution.
https://www.entsoe.eu/news/2026/03/20/entso-e-publishes-expe...
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.
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.
The day after the system goes live, they'll probably announce flat rates for any time of day, just to f' with me. :(
I am a staunch DIY serial entrepreneur techie that has used my grey goo to build and sell a few companies and my time now is spent similar to yours although using a different application of physics. I too am motivated, just as you are, in my efforts to apply what I know to further reduce my energy costs which will not stop rising for quite some time.
You really made my day with this post and I hope we can find more folks like ourselves from your share because in time 'dogfooding' new ideas at home will lead to new applicable discoveries for all.
Stay Healthy!
https://www.youtube.com/watch?v=IA15VkLlx-w
Its like a large freezer gel pack.
Enjoy.
Every system like yours works to flatten the prices, but it looks like a pretty big swing between peak and off peak pricing today, so it'll probably be a while before flat pricing again.
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.
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).
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.
Why? Overall transmission cost are defined by highest possible consumption, and solar panels have practically no effect on that parameter.
Just how many natural disasters do Americans go through before realizing that?!
These disasters are rare though for any one person - a few happen every year, but it will be years between you personally seeing a disaster. That is why generators sell out when there is a storm: even if you have a generator odds are it is rusted and won't work. It is a waste of money to buy a generator before you need it.
This is one of the most condescendingly-wrong posts I've ever seen on this site and you should be embarassed for writing it. The beginning was just typical hn hubris that I probably wouldn't have responded to, but that last jab at the end in the context of an active and ongoing emergency that you clearly know nothing about is completely insensitive and gross.
Having traveled to those areas many times to assist with recovery, slept in trucks for weeks, and made many friends in those areas: It's day four without power and that is not abnormal. Bigger storms you can go weeks without power. Batteries aren't gonna cut it.
And gas generators have a whole mess of problems.
- Gas doesn't store well. Your stored gas is gonna go bad. That means when you find out a hurricane is coming to your area you can spend your time either protecting your house or wait 3-6 hours in line to hopefully get some gas for your generator before it runs out. Maybe they are rationing to 5-10 gallons.
- They might not work after sitting for years, even when properly maintained (one of my friends had two and neither could get running even with help). Hurricane areas are humid: generators rust. If you don't use gas engines the seals dryrot. If you leave them sitting with gas in them the ethanol (sugar!) Separates out and gums it up, breaking your generator. If you stop using your generator in the wrong way then you'll break it (you need to run it dry, using/wasting all the gas in the tank).
Even if you score gas and your generator works that brings us to the next problem:
The gas stations can't pump gas if they have no power themselves. They also can't be refilled if the big gas tankers can't reach them due to trees blocking roads. Main roads become passable quickly, side roads might not work for weeks. Cell phones might be out for weeks (and modern 5g micro-sites will take even longer to get fully rebuilt across a whole county). If your close-by station can't get gas you can't just call around to fine somewhere that does. You can't just drive around either. Single lane roads mean going anywhere takes forever and you are actively hindering recovery efforts. There are still stations in florida unable to pump gas due to shortages or power loss. So your couple of gas cans got you through a couple of days, what now?
And gas generators have moving parts. They are complicated. Another friend there had theirs die the day after the hurricane. Shit happens.
There is a reason prevalence of gas geberators in hurricane areas is less than 5% (I probably hear one running for every 50 houses, but most run them only intermittently) and it isn't because they're just dumb hicks who aren't as smart as mschuster91.
Lastly, you need to know how to use one. Every time there's a hurricane someone puts it in their garage and poisons themself and their family to death. Should you know better? Yes. But everyone doesnt.
Then there's all the other ways you suddenly need to spend energy to survive: you need to boil water, sometimes for weeks (while you don't have power), you need gas for your chainsaw to clear roads/trees so that power and water can be brought back. You need to drive to get supplies. Wasting gas that could be used to recover from the disaster isn't wise.
Back on topic: A stack of solar panels that could plug into the same outlet as a fridge would be a godsend for a lot of people (while also storing better than a generator and being more compact -- so more can be trucked in after a disaster.)
This is a nice grassroots technology that lets motivated individuals take action.
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.
They’d also probably depend on a power signal to frequency match.
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.
In the original example, RCD/circuit protection is regulated on the _property_ side, e.g UK has EICR for electrical install. Once its done for a property, its good until next inspection (in theory)
This moves the protection to the _appliance_ , which while it needs to meet certification, is much harder to police a consumer electronic device, than a physical unmovable premise.
I think these are great, but there will inevitably be devices that don't implement the spec correctly that still get sold to willful or unwillful consumers that result in danger to everyone.
I think this is probably fine, since UK circuits are typically 20A. Apart from fault current (which would have to be line to line, since line to ground would trip the RCD), it's quite hard to end up with more than 20A of stuff plugged into regular sockets unless you're overinvested in portable heaters. All the big stuff - cookers, heat pumps, showers - is on separate breakers from the sockets.
Circuit breakers trip bidirectionally, so the circuit breaker itself would protect if too much current is drawn through to the mains panel.
How, precisely, would you get 65A through the wiring on this 40A circuit, if I drew 40A of consumption and had 25A of supply?
The 25A cancels out the 40A, so the upstream feed would only see 15A total. You do get 65A of total current drawn through the breaker panel, which is a concern, but the supply wiring would not see 65A. Subpanels (which, this would be a subpanel if it only had 40A capacity) are typically going to be just fine.
In the UK you typically make a ring circuit. In the US you make branching circuits.
In the US you get: Mains -> Breaker -> Outlet 1 -> Outlet 2 -> Outlet 3.
In the UK you get: Mains -> Breaker -> all outlets -> Breaker
In the US, assume I had 65A of load on outlet 3 -- I've plugged in too many things into a surge protector. Assume a bunch of solar panels are on outlet 1.
The the diagram looks like: Mains -40A-> Breaker -40A-> Outlet 1 -65A-> Outlet 2 -65A-> Outlet 3
Now, the breaker won't trip because only 40A are crossing the breaker. But 65A are on the wire between outlet 1 and 2 and between 2 and 3.
Either way, your scenario of a multi outlet branch circuit on a 20A outlet would also not be correct. Let’s just make it simple: 20 amps of solar gen and 20 amps of power gen, connected as follows:
Panel -> Breaker -> Solar outlet -> hairdryer outlet
The current would flow from the solar outlet to the hairdryer outlet fully, and the measured current through the breaker would be 0. All wires would be at 20 amps and therefore safe. (Lets ignore that 20 amp wire is only rated for that temporarily… continuous draw would be 16a…) No violation of any current limits and no danger.
Now, you could go crazy and connect 30 amps of solar and 30 amps of hairdryers and that would be dangerous, but we’re rapidly getting into the realm of incredulity. As soon as you removed the load/hairdryers you would pop the breaker.
Then someone puts two space heaters at the end of their branch circuit, they could easily exceed 20A without tripping the breaker and without straining incredulity.
And you are right, 40A was a silly choice, I figured bigger numbers made it more obvious the problem. But it's not hard to construct a likely example on a 20A circuit either.