I would generalise this a little: The problem with buying a complex item is information inequality. The seller knows more about it than the potential buyer. When inspecting the item, the buyer therefore looks for signs of hidden defects or for evidence that the item is in good condition overall. In this way, cleanliness becomes a proxy for the general condition of the object. Similar mechanisms are at work elsewhere too. Take job applications, for example. A sloppy application is a red flag, even if the applicant’s references are excellent.

Also you don't need anything fancy when washing them, their surface is just glass.

A patchwork of eg new paint is a good signal they're covering something up too

Exactly the same reason you should probably clean the rest of the house when you're selling it.

Theoretically, the price of the house before cleaning should be equal to the value if the house after cleaning, minus whatever the cleaning costs. In reality, you'll get much less for your house without cleaning it, because human emotions.

I agree. Doesn't matter what you sell, you will get a higher price if it is cleaned and tidy when presented to the market - because the kinds of people who pay higher prices are looking for clean and tidy things.

Eh, compared to what though? Compared to speaking to licensed electrician, definitely. But compared to doing a raw web search and trying to put the information in the right order for the application you’re currently working on, I think it’s at worst a wash.

> You can still wash the panels but I suspect it won't be necessary if there isn't too much dust accumulation? Isn't rain supposed to wash away the dust? What am I missing here?

In places where solar panels are used the most, like the Southwest US, there isn't much rain to speak of. Panels get a lot of dust accumulation from Feb-Nov typically, just when they're needed the most.

The author had ground level access. In that case, A microfiber covered sponge on a pole with a 5 gallon bucket of soapy water is probably the easiest thing. Especially if you do it annually, the dust wouldn’t be completely caked on requiring scraping and excessive elbow grease.

I do a similar procedure for my house windows. I use a squeegee on those but probably not necessary for panels.

The system in question does not have a transformer so a grounding rod is not required as it is not a separately derived system.

The equipment grounds should be tied together to prevent any difference in potential though.

Solar gets lots of subsidies in the UK. Homeowners who installed it 10 years ago get a ridiculous payment for generating excess, even if the grid doesn't use it.

> solar does not need artificial subsidies, and can pay for itself

That's true now, but wasn't true when those panels were installed. There were subsidies available to get the market kick-started.

They consist of an extra payment for every kwh you generate on top of the payment for delivering the power to the grid. The amount varied depending on when you signed up to the scheme, but at certain points it was as much as 50p/kwh (+ inflation, so more than that now).

We had a contractor doing repairs before we sold our house. Without being asked he took an orbital sander to the wooden hand railings along the stairs to the front door and said "people really notice this".

A family came for the tour and before walking in the father put his hand on the rail, looked up at the house, and said "this place seems well maintained". Then they bought the house after a small pleasant (for us) bidding war.

The contractor earned his high rate and then some.

when it first started it was basically 450GBP/MWh (In 2010 GBP). and that was paid for every kWh generated (whether exported or not). And the PPA lasts for 20-25 years.

> because human emotions.

If I tour a house with pet urine stains all over the carpet, it's only logical to conclude that the owner is likely not maintaining the rest of the house to a very high standard.

It's not just emotions, it's also a matter of time and uncertainty.

I was in a buying situation where my old lease was expiring soon, I had a second kid on the way, and the last thing I'd have wanted is to buy a place where I'd have contractors milling around for weeks or months to make various repairs. I was willing to pay a hefty premium for a place that's in a move-in condition.

I don't think this extends to "you'll get $10k less if you don't vacuum", but it's a common courtesy on a million-dollar transaction to maybe not leave a mess.

See also why houses are often painted when being staged for selling just so that the new purchaser can paint immediately after with their preferred colour. Wasteful but it works.

It’s not just emotions, it’s a sign that, when presented with something annoying that you should do but not strictly required, it shows that you pushed through and did it anyway.

It doesn’t prove that you’ve been generally on top of things for the lifetime of the house but the inverse situation where you couldn’t clean one time for guests sure doesn’t.

It's perfectly rational to assume someone who didn't bother to clean the house before selling probably didn't take good care of the house in other, less visible ways.

> In reality, you'll get much less for your house without cleaning it, because human emotions.

It's trust, because if the previous owners can't even bother cleaning it up, what else might their neglect have done to the house? Maybe I'll need to change the house wiring, verify if any new paint job is hiding mold or infiltration... All that is the cost of uncertainty and uncertainty grows with distrust.

This simple procedure increases the selling price of everything. Just a fact.

Some places don't get much rain (and these are the places that tend to get even more dust - e.g. deserts).

Look at any outside surface in a rainy climate.

The dirt may not be piling up, but it's far from clean.

As another anecdata-point, when we did this for a now already fairly old roof installation of about 15kWp, it was more than “just about worthwhile”, since the panel area is contiguous: cost seemed to scale up less quickly than the wattage/theoretical maximum output, and the cleaning guy (solo company, IIRC) even told us it wasn’t necessary to do this every year (we hadn’t had it done even once the first decade+ of the installation’s lifetime).

So, at least in our case, definitely worth it.

In many countries it is actually illegal to use tall ladder etc. owners would have to erect a scaffolding to make access for work people to clean it safely.

> I am not sure what author is trying to hint. But solar does not need artificial subsidies, and can pay for itself!

I think he is describing a subside that some governments gave years ago: you installed for example 5K, and get paid for whatever they generate at 300% market price, for a long time (25 years?). Today you find out that upgrading panels would made perfect financial sense, if you were selling at 100% and are going to sell electricity at 100% (you will be doubling the output for a tenth of the inversion 15 years ago), but as the subsides of 300% no longer exist, you will be actually losing money by upgrading.

Having recently bought a house, I love thinking about things that increase perceived value relative to cost (more so because they're nice to have, not because we plan to sell any time soon).

A few things we changed right away: - new mailbox (replacing a rusted 30+ year old one) - lots of landscaping work (the majority of which I can do myself) - installed a wine fridge (I always felt it gave the sense that the kitchen was upgraded when we were touring places) - replaced old door knobs with modern matte black levers; ~$50 each

The house was built in 1968, so it's been interesting to think about all of the small things that make it feel dated that can be changed for not much money.

> because the kinds of people who pay higher prices are looking for clean and tidy things.

I'd say it's also "because the kind of people who clean and tidy things also maintain them"

See also "staging":

* https://en.wikipedia.org/wiki/Home_staging

It may also be worth spraying them with water when they are too hot. As they get hotter the efficiency drops a little. It's only a few percent, and usually it happens at the time you need the efficiency the least because it's sunny, but if you can combine cleaning and cooling and get a few extra w out if it, why not.

There are many different ways to connect solar panels to the inverter. Usually the exposed metallic parts will be “grounded” (bonded to the ground / protective earth / equipment grounding conductor / whatever your jurisdiction calls it at the inverter).

But this is an array that looks a bit remote from any structure, and even if the electronics themselves are utterly, perfectly safe, the bonding wire will cause the panel frames to be at the potential of the inverter’s ground, and the soil will be at whatever its local potential is, and this may be different, resulting in a “touch potential”. You can mitigate this with a supplemental ground (or whatever your jurisdiction calls it) closer to the panels. There are fancy ways to do this particularly well to improve safety in the event of a fault.

If you are contacting the actual power wiring of the solar array, something is wrong. If you are feeling capacitive coupled current from the power wiring of the array, then I imagine this means your inverter has crappy filtering, and again the only way you would feel it is if the panel frame isn’t at the same potential as the local soil.

Oh, and if you live somewhere prone to lightning, you probably want to give a possible lightning strike to the panel a better route to a high quality ground than through the bonding wire to your house.

(In fact, in many parts of the world, including IIRC 48 US states, the power utilities may operate their distribution networks with a current carrying wire (combined neutral and ground) that is grounded at multiple points along its route, which will generate substantial leakage current through the ground. The exceptions are IIRC California and Wisconsin, and IIRC those states have their rules to help protect cattle from becoming part of an undesirable circuit while being milked. In CA at least, all the distribution transformers on the poles have at least two bushings on the primary side, and this is why. I believe this is California General Order 95, rule 33 [0].)

[0] https://ia.cpuc.ca.gov/gos/go95/go_95_rule_33.html

People often confuse "irrational" with "rational on inference given incomplete information"

This is the latter.

See also: stereotype accuracy

Interesting; what was on the panels? What was the ROI on paying the guy?

That's not true. You can upgrade to the same capacity on the previous feed-in tariff and keep what you had. It makes sense to upgrade as you can then fill the extra space with additional panels (which will not be on the old tariff, but can be a separate system).

To add a few more: it's similarly easy to swap cabinet handles, vent covers, outlet wall plates. Fresh caulk is nice too, even if it's a bit sloppy, still beats stained or cracked caulk.

Definitely. On the other side, if you can't even bother to clean it before you sell it, I have no reason to believe you've put any effort in maintaining it.

Cleaning in general is also usually a core part of maintaining something. Dirt and grime lead to wear and tear.

Yes, I meant I can get on board with automatically (periodically or based on some trigger or sensor) spraying the panels with water but I was hoping it isn't necessary to use Windex® or even dish soap on the panels themselves.

Exactly. "Is it clean and tidy right now" is a decent proxy for "Has this been properly taken care of in the past"

Obviously it's not infallible. But even if the owner only cleaned their stuff now that they are selling it that still tells you they are the type of person to take action where it's beneficial

Why is it written like that lmao

There are definitely some wacky nanny state rules out there… but I’m a little skeptical of “In many countries it is actually illegal to use tall ladder”

Solar panels are increasingly being oriented east or west instead of south, as while it reduces overall yield, it maximises power when it's needed the most - during morning and evening peaks.

I don't have numbers, but I suspect it alleviates issues with dust buildup and temperature.

> The drop off after cleaning could well be because some of the initial boost could come from the water cooling off the panels: solar panels become less efficient at higher temperatures so the drop of after they're all cleaned could be them warming up again after the water has evaporated.

This was almost certainly the case. AIUI, that cooling still makes a large difference.

Makes me wonder if it is worth it having a small esp32 or similar control a sprinkler system for the panels. Keep them cool during high ambient temps by spraying a litre of water on each panel every 30m.

An idea I had a while back (when I was considering panels) was running my mains water through the back of each panel (before the mains got to the hose) in a sort of radiator pattern.

People make the same claims about cleaning their air conditioner. Yeah it’s blowing cooler inside: you’ve just chilled the condenser and left some residual evaporative cooling.

> "Is it clean and tidy right now" is a decent proxy for "Has this been properly taken care of in the past"

I don't think so, esp at selling time, I definitely expect that the owner has just made it look pristine. But the opposite is definitely true: if you can't even bother making it look clean and tidy when trying to sell, I'm pretty sure you've not taken care of it in the past!

Funnily enough, there was a thread a while ago here where people were fixated on the idea that you had to wash solar panels, and thus proponents are underestimating maintenance costs. I had wondered where that idea had come from, as I thought it was fairly well understood that even quite dirty panels once much of an efficiency drop…

I asked a friend with a window cleaning business and they charge about $10 a panel. At that rate I'm tempted to try it but I'm not sure if it's even worth that.

Where I live we don't get much rain, have a lot of dust, and I have a pine tree next to my house that sheds sap onto the panels. That means they get pretty filthy over a year. I pay a guy $150 once a year to come clean them off.

The gains are marginal, I'd have to do more research than I feel like doing to get hard numbers weighted against weather conditions, but I'd guesstimate around 300-400kWh more output per month.

SDGE gives me $0.3-0.5 per kWh during solar peak, so I'm breaking even after one month, and it makes the house look nicer, so I'd call that a win.

Its an easy value add for a pressure-wash / soft-wash business

I think it's more of a negative indicator. It's like turning up to a job interview wearing dirty clothes - unless you're a savant it's probably indicative that you don't give a shit or have some sort of other problems in life. But wearing clean clothes doesn't give you points because it's assumed to be the norm in that setting.

Wikipedia is written by various people, but likely someone with interest in a given topic. One or more realtors probably wrote or edited this post.

Actually, the history of edits shows that this is contested territory where people regularly remove what they term as spam links. So, while a disinterested editor might remove a link to a listicle about how to stage your home, they might leave in the breathless tone as harmless. The drive by editors probably feel that they have no more time to rewrite it than we do, given that they watch over many articles, not just this one.

Its been "staged"

Right. Clean house on the market means almost nothing.

Gross house means almost certainly not maintained.

Probably the GP meant to hire people and order them to use a tall ladder. I don't think there's any country where it's illegal for you to use one outside of some kind of contract.

Tracking systems are also becoming more popular. You spend a little more up front but get a lot more usable power.

isn't that more of a storage issue, which a home battery would solve?

Yeah, came here to say this. There are a lot of things that will affect efficiency and how clean your panels are is only one of them. How dirty your panels get is also highly sensitive to both location and installation. All of this gets horribly confounded by string inverters (especially if they're clipping the peak, which they often are).

I easily see 5% increases in efficiency after cleaning (with micro inverters), but also see ~3% increase in output on a hot day from just spraying the panels with water to cool them off, which goes away in 15-20min.

If you're going to clean once a year, do it after the "last" rain of the year before summer peak solar output. If you live somewhere rural with summer thunderstorms, with high angle panels, and without a lot of pollen (or dust storms), you may not need to clean them much at all.

If you're going to climb on a roof, do it safely! A 10' fall can kill or maim you.

My solar panels are leaning in stacks in my yard, as our house is currently being removed with a new roof, etc. I'm planning on cleaning them while they're "loose", but I wonder if it also makes sense to apply a(n automotve-style) ceramic coating to them.

20% seems high enough that if it was really _that_ effective, the companies making the panels would be tripping over themselves to buy this coating to apply it to the panels right in their factories. (And charge a premium for it.)

Tradespeople are typically independent contractors. You hire them to do a task, and they use their own judgement on which tools to use. You don't order them to use a tall ladder...

Without trying to answer your "I believe the setup circumvents the fee" implied question, which you should find an actual answer to...

See reddit's r/solarDIY. There are a lot of setups like this, either for full house power or partial. I have a relatively big server in my basemeent that I power this way, for example, with a battery system that acts as both UPS and a "charge the battery from solar and run off inverter when possible". Something like an off-grid EG4 is popular among the reddit crew as a way to manage this; the device tries to run locally but accepts a shore power feed from the grid so if you need it you draw grid power. No grid tie involved.

Having just put a battery into my existing system. For the power company I use the answer is no to your question. Many power companies charge that fee depending on the size of panels. Now if you do not hook to their system they do not care (off grid). But if you plug into it then they care and charge for the privilege.

Now you could pull particular items out of their grid. Just need the wires and panels to make sense. They would not care about that either. It is only if the panels are plugged into the grid they start to care. Downside is sometimes waiting for that battery to have enough juice to work. It goes faster than you think and some battery systems are decently expensive just by themselves, on top of the panels/inverters/controllers/install.

That depends on what options are available to you for residential solar installation. Installing solar panels + micro-inverters is very cheap in cost of parts, but possibly expensive in labor. It will easily pay off your grid interconnect fee every month once you hit break-even from operating for a few years. Financing vs cash, cost of installation, tax credits, are the biggest factors in how quickly it becomes profitable. If you are extremely handy you can DIY most of it as a homeowner (depending on local/state laws) which cuts costs significantly.

You can do a whole home backup + solar panel input (aka ESS+PV) but it's much more expensive in parts and installation and is more complex. If you don't add grid interconnect it can be much cheaper as you can use "off-grid" parts (grid interconnect requires more expensive parts certified for certain standards).

But some jurisdictions may not allow cheaper "off-grid" parts/systems to be connected to the grid, even downstream. So an alternative would be to install a transfer switch, where you manually switch from the grid to off-grid. But then you literally have to choose whether you use the ESS+PV or the grid at any given time and manually throw a switch (you can't use grid to charge your system). And yes you can set this up for only specific circuits/appliances. Again it depends on your state and local laws.

AI can do most of the research for you. Keep a Git repo and add documentation and details to it over time, and you can build up an analysis of what works for you based on all available options, price comparisons, energy requirements, and local/state laws. It is unfortunately quite complicated because there are many options but not all will apply to your location. And before you do any of this, do a solar site survey to see if you can even reliably generate enough power from the sun!

On Mars, the wind storms and dust devils are so fearsome that some of the robots there could rely on dust being blown clean off all the solar panels on a regular basis. Spirit and Opportunity benefited the most from these effects.

InSight was stationary and not so fortunate. But, the ground team got quite creative with its robotic arm to try and manipulate the sand that had accumulated on the solar panel, and gained a little bit more power.

https://en.wikipedia.org/wiki/InSight#Surface_operations

https://en.wikipedia.org/wiki/Martian_regolith

> I believe that setup circumvents the fee since the only thing using energy is the battery, as though it were an off grid setup.

Entirely based on your jurisdiction, but that kind of zero-export requires the same permits and connection fee as a full net metering in mine. You can't end run the process by just being sneaky, electrical work needs permits and they'll either make you take it out (!!) or bring it into full compliance.

As an example, my utility is one of those ones that requires a separate manual disconnect, even though the vast majority of all-in-one inverters have a built in disconnect. It doesn't make any sense and it's at least two grand in permit + equipment, but that's the rule.

Yeah, the one tree branch that hits my array until 10a prevents it from charging at all even though it only obscures 1/4 of one panel in the 10-panel set.

But I like the branch and have plenty of full sun, so I haven't cut it.

Storage is one way to move time of supply to match time of demand. Offsetting the time of supply directly is simpler, although it probably doesn't offer a complete solution.

The most interesting trackers to me, for DIY install in my yard, is a 2-axis tracker. Especially in summer, sunrise and sunset are quite a bit north of east and west, meaning a true south facing fixed set of panels wouldn't even see the sun yet.

Sadly, my investigations a few years back indicated that a suitably strong and robust 2-axis tracker that would withstand our local winds and snow loads is significantly more expensive than just buying more panels and facing some of them east/south/west to accomplish the same thing. Doing this on an existing shed also avoids some local zoning rules vs a dedicated ground mounted system.

The upcoming "balcony solar" legislations will allow up to a limit (iirc 1200W in Virginia) of solar to be directly be connected to the electricity outlets of a house to make our electricity costs lower without having to pay for a battery from what I understand.

A battery would solve it, but it can be cheaper to have additional panels oriented east and west than to add the equivalent battery capacity

Panels are so cheap now you're better off just installing twice as many without tracking.

I am curious how much of a difference it makes.

I have 4kw of panels and 15kwh of storage. I only get down to about 80% most nights (I heat with wood and propane).

But my system will charge completely in about 2 hours of full sun. If it took 3 hours it wouldn't make a difference. So I generally don't clean them (well, the rain and snow do that work).

I do remove snow, because that has a very noticeable impact.

Is the difference that you are pushing back to a grid (I am not), so the power all gets used regardless of you being the one to use it?

Ask a lawyer about the law.

> I clean my solar panels, 7kwh, every monmth or two.

This honestly sounds like a non-trivial strike against installing solar panels, especially if they’re installed on tall roofs.

I definitely wouldn’t want to have to clean them that often, or pay to have them cleaned that often.

If you’re spending only 10 minutes on them, then maybe you don’t have that many, and they’re not up high.

If export energy is 10% of your total output, and it jumped 35% then you got a ~3.5 - 4% gain in total output, not far from the author's experience.

Of course, you can math that any way you like to make the numbers bigger or smaller, depending on whether you're representing the buyer or the seller of the system.

Rain usually just cakes the dirt. Unless it's a downpour, it doesn't move with enough velocity or volume to remove the dirt. So the dirt just gets damp, maybe moves a few cm with gravity, then dries as a mud cake.

my experience is that unless you get some really torrential rain, it's not enough to clean the sand/dust/grime

I get the impression they are getting less viable because the extra cost and maintenance outweighs just putting more panels down. There are some calculations that suggest even mounting them on angled frames might not be worth the cost, depending on how dirty they get when you just lie them flat on the ground.

(This assumes that you have enough space, but for grid-scale solar this is not the limiting factor. The costs are roughly in order from most to least: the cost of the inverters and grid connection, the cost of installing the panels, the cost of the panels themselves, then the cost of the land to put them on)

I can speak to this somewhat. My panels are on adjustable frames. Typically I switch from flat (summer) to tilted (winter).

As always ymmv and depends somewhat on your location. I'm around 30 degrees from the equator.

During summer, lying flat gets a lot more power. And more importantly the start and end of the generating period is longer. Ie the panels get more sun in the morning and evening thankfully they were tilted.

In winter the sun is more "from one direction" and obviously is lower on the horizon.

Roof-mounted solar panels are a necessity in urban situations but they are a maintenance nightmare compared to a ground-mounted array. That has to be accepted as "the cost of doing solar" when there is no other alternative.

I never cleaned mine. Rain does enough. It's still plenty valuable without minmaxing them.

On tall roofs there tends to not be much dust.

Why would I ask a lawyer for advice about whole home battery solar setups with a grid backup?

See this all the time in Phoenix metro: A light rain just pulls down all the dust in the air and deposits it on the car. It has to be fairly sustained to wash away the initial dust collection, and even then you can still see dust on the paint.

It's not 10%, it's much more than that. I'm obviously comparing the peak values, which tend to be days when we don't consume much, which might mean a background 100W vs a couple of kW peak generation. I can dig deeper into the per hour generation and it's similar.

Mine are not on a roof.

Can confirm, my car doesn’t get cleaner unless there’s a downpour

I'm off grid, no mains power, and have 8x48v lithium Fogstar batteries in an external rack, since my cabin is small.

On December 21, due to trees, my panels get around 2 hours of full sun, if the universe smiles on me.

I use around 5-6kwh per day, if I use my computer, which I need for work.

This will be the first year with the fogstar batteries, previously had 1x48v generic lithium battery, but last year I used the generator most days from around end of november until March e.g. December consumption was 153kwh, solar generated 62kWh, and generator made up the rest.

This year, thanks to having more storage, we'll be better able to take advantage of sunny days and capture more power. I also have a freezer and washing machine this year :-) Ask me in March how it went.

All of my panels are easy to access, none on a roof, so the effort is minimal and has non-zero power benefits in my experience.

I should add that I am surrounded by trees and the panels accumulate a green tinge quite quickly, plus bird shit.

Because often the law cares about intent, not technicalities. Technically you could argue that this is a "whole home battery solar setups with a grid backup", but clearly the intent is as a workaround.

I'm not saying this is bad. I love a good workaround for onerous laws & fees, but random Internet commenters aren't the best at determining what workaround will or will not pass muster if a judge gets involved.

Like someone said in another recent thread: "U.S. law though is highly non-autistic and what you were trying to do is just as important as what you superficially did." https://news.ycombinator.com/item?id=49064242

Because you're asking legal question about what the law allows, not a technical question about how to exchange voltage and current.

I can see how small efficiencies would matter a lot in that sitation.

When I had 6 100W panels and was trying to keep my laptop (and lights) running off that, then I did a lot more trying to keep them clean. If I was having to burn fuel for electricity, I'd certainly be trying a lot harder to squeeze what I can out the array.

Anyhow, good luck.

I likely am in a similar position. My hope is to get a cistern buried this year so I can have more than 40L of liquid water on hand at any given time... and then maybe even a shower :D Washing myself with a bucket is starting to lose its charm.

> I also have a freezer and washing machine this year

You need a heat pipe between your freezer/fridge and outside. Then it will “function” when it’s colder outside than in your fridge and otherwise sit idle(ish). Sure you’re bringing “cold” into your big warm box (home), you have wood to overcome that. All theory, but it makes sense in my mind!

(Though in most places, it rarely gets colder outside than in your freezer)

There is a lot that loses it's charm, lol. Started with an outside kitchen and shower, which was fine in the summer but in the winter when the wind blows and it takes 30 mins to heat a pot of coffee the charm wears thin, lol.

Good luck to you too!

It's fun to meet the basic challenges head on though, eh?

My chest freezer is in a barn and is designed for it's place and purpose.

My fridge is indoors, where the wood I chop today will keep us both warm in the winter.

Thank you for your theory, but I'll stick to doing the practical that you read about on the Internet.

If they are like me, keeping the fridge from freezing during the winter is more energy that keeping the fridge cooling during winter...