Should you wash your solar panels?

7/27/2026 at 1:46:10 PM

> why would you clean them when you're about to sell the house?

So they look good and the potential buyer sees something that looks to be in good condition and working well.

by wodenokoto

7/27/2026 at 2:56:56 PM

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.

by Archelaos

7/27/2026 at 7:29:19 PM

Aka: a heuristic: https://en.wikipedia.org/wiki/Heuristic

by Scoundreller

7/28/2026 at 7:19:22 PM

Brown M&Ms:

<https://www.npr.org/sections/therecord/2012/02/14/146880432/...>

by dredmorbius

7/27/2026 at 5:08:45 PM

"Information inequality" is known as "risk". Risk is inherent in any transaction. That factors into the price: one is willing to pay less the more risk there is, and will pay more for less risk.

by WalterBright

7/27/2026 at 7:31:01 PM

Much too simple.

Most "risks" have an upside and a downside. In this case, for example, the solar PV system may be working better or worse than the (potential) buyer initially comes to understand.

We have huge industries based on selling "risk, but with a huge potential upside" to people willing to pay for access to the potential upside. Many of those customers are not interested in low risk in that context.

So "more risk, pay less" is not a hard and fast rule, but depends on what is being purchased, the circumstances of the buyer, and more.

by PaulDavisThe1st

7/27/2026 at 10:11:01 PM

The Black-Sholes equation is an attempt to calculate risk. Of course, risk is difficult to pin down to a number, and different people will assess risk differently.

But that's irrelevant to my point, which was that risk is factored into the price.

by WalterBright

7/28/2026 at 2:23:34 AM

You made a very specific claim that more risk == lower price. That isn't true as a general rule, though it may be true much of the time.

by PaulDavisThe1st

7/27/2026 at 2:24:50 PM

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.

by delusional

7/27/2026 at 2:47:04 PM

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.

by delichon

7/27/2026 at 5:12:45 PM

A real estate agent told me that a customer decides to buy/not buy a house as soon as they put their hand on the front door knob. If he decides to buy, he'll look at the rest of the house looking for a reason not to.

I.e. putting in an expensive door knob is a good plan!

by WalterBright

7/27/2026 at 5:30:58 PM

Also make sure the door operates smoothly and is well-aligned.

by HPsquared

7/27/2026 at 9:26:16 PM

> A real estate agent told me

Whatever you wanted to hear to make them the most amount of money in the(ir) least amount of time.

They are the sellers agent.

You should not trust them a millimetre further than that.

(I bought my current house based on a spreadsheet analysis. Doorknobs are easy to replace, foundations, walls, electric, a lot harder.)

by brnt

7/27/2026 at 10:00:06 PM

You seem to be assuming that the real estate agent was in the process of selling them a house.

by arcanemachiner

7/28/2026 at 12:21:36 AM

A good friend of mine is a real estate agent. I have never retained him. He's a fountain of good advice, though. He's the most successful agent in my community.

BTW, a so-so agent will lie to you. The ones on the top, however, are that way because they get repeat business.

P.S. Read books on salesmanship. It will inure you against slimy sales pitches.

by WalterBright

7/27/2026 at 7:47:39 PM

There's a reason the three most important things in real estate are "Location, location, location"

by lotu

7/27/2026 at 7:55:23 PM

None of those are "door knob, door knob, door knob!"

by jawilson2

7/28/2026 at 1:56:57 AM

I was confused by the parent post too. Perhaps they mean that you see the neighbourhood before you even see the house. A little like the first impression of the house is made before even seeing the actual house.

by red369

7/27/2026 at 6:29:58 PM

Certainly wasn't the case for any of the houses I've bought. All were compromises in various ways; none were houses we loved on first sight.

by SoftTalker

7/27/2026 at 7:02:23 PM

Have you ever driven by a prospective purchase and never bothered to get out of the car?

> All were compromises in various ways

That's true of just about everything.

by WalterBright

7/27/2026 at 7:31:28 PM

No, if we took the time to go to the place, we at least looked at it. I don't remember ever driving up to any property and just turning around.

Did we rule looking at something based on photos/descriptions? Yes, certainly.

by SoftTalker

7/27/2026 at 10:06:28 PM

Photos tend to focus on the house, not the setting. A big deal for me is the relationship of the house to the sun, the neighborhood, the view, privacy, traffic, noise, etc.

by WalterBright

7/28/2026 at 12:45:02 AM

Even a house you know you're not going to buy is worth taking a walk-through if you're already there and the agent has prepped it for showing.

You can learn a lot from such experiences. What to look for/what not to look for, etc. Sometimes the wrong location will have the right house and you can dial in precisely the things that matter to you so you waste less time on future showings.

Of course if you're highly experienced and on your 4th house purchase the value for your time may not be there. But I've found it quite useful over the years - especially when looking at different property types than I'm experienced with.

by phil21

7/27/2026 at 11:18:21 PM

Maybe it's just me, but someone deciding to physically sand things without my consent would get a stern eye from me. Unless it's well into the "no brainer" kind of decision. (eg: the railing didn't have a finish on it, etc).

by switchbak

7/27/2026 at 2:29:53 PM

> 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.

by pton_xd

7/27/2026 at 7:58:51 PM

OTOH, spotless carpets do not really tell you the opposite is true. Just means the realtor doesn't suck.

by rootusrootus

7/27/2026 at 11:20:01 PM

Absolutely - in some cases you'll see the major sins addressed, and there's a small mountain of lesser issues waiting to be uncovered.

by switchbak

7/27/2026 at 9:16:26 PM

That’s exactly how you get a good price though

by baq

7/27/2026 at 10:08:43 PM

"Bring your vision!"

by senderista

7/27/2026 at 2:42:43 PM

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.

by harrall

7/27/2026 at 5:02:37 PM

There are other reasonable interpretations of such things. More precisely, one may simply care in different ratios about various things than is typical. For example, one may be fastidious with replacing furnace filters and water heater anode rods while not caring about their lawn beyond city or hoa mandates.

by john01dav

7/27/2026 at 2:47:08 PM

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.

by austinl

7/27/2026 at 3:02:56 PM

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.

by dlubarov

7/27/2026 at 5:48:23 PM

Those are things I've noticed when I've shopped for homes.

Mostly, I notice that they look like efforts that were motivated by trying to get a high price, but are limited to being fast and cheap.

So while I do note them, my perception of them is not generally positive at all.

I'd rather the outlet covers be original and clean than the new, usually oversized covers (with a slight color mismatch) I often find.

If I'm seeing caulk anywhere, that's problematic for me. When used properly-sparingly to seal things, it doesn't draw the eye at all. When it's used to hide sins, it's awful.

When I see sloppy caulk I first think of the time I'll need to spend to dig it all out. And then, I think about the time it will take to actually-fix whatever things it was hiding that nobody has ever bothered with actually getting right.

When I see new doorknobs on old doors, I'm mostly attracted to the outline that was left by the original hardware. And then I wonder: The old knobs were probably made from materials like steel, cast iron, and brass; stuff that can last for centuries with some maintenance. Why were they replaced?

Were the old knobs non-functional somehow, or were the owners too cheap and lazy to bother with taking things apart for a bit of TLC and preservative paint?

What other parts of the house were done fast, cheap, and/or lazy like a landlord who doesn't give a fuck? What haven't I found yet that they "fixed"?

by ssl-3

7/28/2026 at 2:31:37 PM

I think it's safe to say you're in the minority. Empirically, "fast and cheap" cosmetic upgrades like repainting usually more than pay for themselves.

> I'd rather the outlet covers be original and clean than the new, usually oversized covers (with a slight color mismatch) I often find.

Any task can be screwed up if someone is careless enough, but this is extremely easy to get right. If a standard cover plate fit before, it's trivial to buy a replacement of the standard size and appropriate color.

Cleaning works too, I personally just wouldn't bother cleaning a part that costs ~$0.50.

> When I see sloppy caulk I first think of the time I'll need to spend to dig it all out.

Would you really rather see cracked caulk, which means (a) the original contractor probably used whatever cheap rigid caulk he found in his van, (b) it's been letting water through instead of sealing, and (c) noone cared enough to fix it?

by dlubarov

7/29/2026 at 7:06:02 PM

That's the problem: Any task can indeed be screwed up. It can be worse than it was before.

A new, not-oversize cover plate that actually-matches in color is fine. As you suggest, it is trivial to get that right.

But people screw it up anyway, and when they do so it represents a distinct lack of attention to detail. If I find that along the presence of other new electrical stuff, like outlets with USB jacks, smart home dimmer switches, and can lights with fixed LED elements, then... man. They obviously couldn't even get the outlet covers right. What else did they screw up, that I can't see?

Old caulk that was skillfully applied and remains in good shape isn't a problem; it is not broken and does not need fixing. New caulk that is well-done isn't necessarily an issue at all. Both communicate that a base level of positive care for the quality of the home was present.

But when it's sloppy, it's a clear indicator that they just didn't care much at all during the process. There's direct evidence that they were unwilling to put the effort into making a smooth bead of caulk instead of a messy one. They didn't care about that part of this small job, and by extension they probably didn't care about what they were covering up (whether it was good, bad, or indifferent).

Anyway, maybe the lazy fixes work for enough buyers that it does increase the sale price, and that's good for a seller.

It doesn't work for me, though. The presence of these kinds of things brings me more questions than it does answers.

---

The answer that maximizes the price by satisfying all potential buyers is to do careful and correct fixes. If the quick fix makes some money, then a good fix makes even more money. Take the time to get it right.

by ssl-3

7/27/2026 at 7:47:50 PM

It’s the faucets and sink fixtures that can jump out at me. I… question some of the Amazon-grade ODDALLCAPS fixtures’ ability to not spring a leak in the long term. Showerheads are more whatever.

by Scoundreller

7/27/2026 at 8:02:52 PM

And the rest of the plumbing. I'm not saying that homeowners can't plumb properly (many do excellent work), but: Too many times, it's just ugly.

Sometimes it's easy to find: The "soft" parts under the sink are a mess. Flexible pressure lines that are a mile too long, bendy pipes on the drain (this should never happen), traps in series with one another, bizarro-world TPCLALL-branded Amazon-sourced parts that simply do not match regulated norms at all and which haven't seen a UPC® logo ever... but that's simple to rip out and replace.

Sometimes it's harder to find. Drains that go uphill. A sea of CPVC pipes running in every direction, with dead ends, all buried in the basement ceiling. No trap for the bath tub upstairs. Mixed metals. Mixed plastics: PVC is fine, and ABS is fine, but mixing them together is bad (and shows that a trip to the parts store to get The Right Fucking Thing was just too much work, since it wasn't done). Bad or nonexistent venting.

The problems of today are caused by the lazy, quick fixes of yesterday.

by ssl-3

7/27/2026 at 8:51:08 PM

And the wiring. Don’t forget the wiring. Bought a place that had a fault to earth. Took demolishing a wall to find it - previous owner had buried an extension flex inside a wall, just concreted over it - and hadn’t even done that properly - mice had gotten to it, and it was a corroded piss-soaked mess.

I have a photo of the original breaker box that looks like bad AI, it’s so unspeakably awful - just this wild spaghetti of muddy corroded wires and parcel tape with bits of string and random breakers floating in midair at jaunty angles, connected sometimes to live, sometimes to neutral, sometimes across circuits, usually doing nothing. The earthing was purely accidental. I just ripped it all out, but not before the microwave bit me one rainy morning.

by madaxe_again

7/27/2026 at 8:42:28 PM

You should see what I’ve seen in France!

I now realize a lot of the bad bathroom smells are because of traps siphoning dry. Tho the general lack of exhaust fans doesn’t help. Anywho, AAVs to the rescue! And mineral oil in their version of a t&p valve if it doesn’t need to drain much to prevent evaporation of the trap water: https://fr.wikipedia.org/wiki/Groupe_de_s%C3%A9curit%C3%A9

by Scoundreller

7/27/2026 at 6:23:39 PM

outlet wall plates

Also make sure your screws in your outlet wall plates are vertical. I've found it's a key tell between mediocre electricians & handymen, and the real pros, and it gives me confidence (perhaps unfounded) that the electrical systems are in good shape.

by aaronbrethorst

7/27/2026 at 6:42:40 PM

That's funny - I always align the screws in the wall plates when I (re)install them, but imagined that to be an idiosyncratic bit of fastidiousness. I've never noticed anyone else having done it.

by marssaxman

7/28/2026 at 12:01:00 AM

Eh. I've been working (at $job) with an electrician I will be thrilled to see the back of, and whom (the feeling is general) we will never hire again, and... The screws are aligned, but eldritch horrors lurk beneath. That might once have been a useful heuristic, but too many have caught on to it.

by eszed

7/27/2026 at 8:05:16 PM

the little rubber gaskets in sink drains for garbage disposals are also a cheap upgrade the brings a place up a notch

by monknomo

7/27/2026 at 7:29:29 PM

I hate when sellers do this. Replace all the finishes and hardware with the cheapest possible hardware from the store just because it is new. You end up paying for a top dollar house (because now you can argue its worth more than comps that didn't get this treatment) with bottom dollar components.

What would be better is not doing anything and letting the new owner install what makes sense to them, instead of having them pay markup essentially for these placeholder finishes, but obviously we can't have any altruism on this capitalist earth.

by asdff

7/27/2026 at 9:46:10 PM

I hate it, too. And obviously, sellers are motivated to seek to maximize the sale price, while buyers are motivated to minimize it.

But if these hacks do increase the sale price: When (if) you find a suitable place that has not had the cheap+easy hardware refresh, then it will tend to sell for a lower price than one that has.

And that's good for buyers like you, and me.

by ssl-3

7/27/2026 at 7:27:15 PM

What is funny is it is kind of going full circle now with the home decor. All the 70s-80s era finishes boomers are currently gutting and replacing with builders special grey modern blegh are actually becoming popular again among millennials and gen z buyers.

by asdff

7/27/2026 at 5:13:48 PM

Trump wrote in one of his books that a person selling their car that does not detail it beforehand is a fool.

by WalterBright

7/27/2026 at 5:43:41 PM

Did he also say you should cover everything the tackiest gaudiest faux-gold crap everywhere?

Anyone who takes business advice from Trump is a moron.

by QuercusMax

7/27/2026 at 6:46:37 PM

If there is one thing Grump does know, it's the value of fools.

by mindslight

7/27/2026 at 7:05:55 PM

i find it extremely hard to imagine that Donald Trump would have ever been personally involved in the sale of a vehicle at the level that he'd be making decisions about whether or not it was detailed, but I guess it's sensible generic advice

by epiccoleman

7/27/2026 at 7:25:12 PM

Visit a used car lot. The cars are all clean and detailed.

by WalterBright

7/27/2026 at 10:08:35 PM

It’s not that a car needs to be clean per se, but you don’t want prospective owners to be distracted by thoughts of the past life the car has had in the care of another human. Nobody wants to touch the indicator stalk that has layers of dirt and finger grease baked into it.

by simondotau

7/27/2026 at 8:26:57 PM

Or in the actual writing of a book, for that matter.

by hfsh

7/27/2026 at 8:56:20 PM

I’d be surprised if he can’t write two coherent paragraphs on one topic.

The bar is low and you’d still need to hand the devil a shovel.

by noir_lord

7/27/2026 at 2:57:39 PM

> 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.

by gchamonlive

7/27/2026 at 2:54:16 PM

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.

by skippyfish

7/27/2026 at 5:11:01 PM

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

It's not because of emotions. It's because it correlates with other neglect that may be less obvious.

A good real estate agent has a rolodex of various contractors that can fix up a house to ready it for sale.

by WalterBright

7/27/2026 at 6:27:37 PM

Cleaning the house doesn't retroactively fix the neglect though. It just makes the house look cared for to the lizard brain.

by svachalek

7/27/2026 at 4:59:37 PM

Being rational about this (i.e., buying a dirty or otherwise manageably flawed house) is a great way to save or make money in markets where the majority of the cost is the building.

by john01dav

7/28/2026 at 8:34:13 AM

For the same reason, get a car with dents, or light obviously bubbling.

by benj111

7/29/2026 at 10:36:23 AM

I did exactly that! 2000 Toyota with dents, a little surface rust, and a good engine and transmission

by john01dav

7/27/2026 at 7:02:48 PM

People always want to make a place their own with renovations, which means a new bathroom, a new kitchen, a complete lick of paint and the list goes on.

They would prefer to throw out an old suite rather than something that has just been fitted to 'sell the house'. The excuse is provided for them to make it their own.

What they don't want is filth. A spotlessly clean house is preferable to one that has been hastily tarted up with a quick lick of paint. It is respect for the buyer.

by Theodores

7/27/2026 at 2:36:20 PM

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.

by BurningFrog

7/27/2026 at 4:46:31 PM

I spend €125 on an interior decorator and another €500 in furniture and decorations after to make my condo more cozy. And then another €300 for professional photos and drone shots.

The photos looked like those fancy interior magazines. I will never know if it is because of my effort and investment but I’m certain that it attracted a lot of attention. People really want a move-in ready home that looks like the magazines.

by retired

7/27/2026 at 7:56:58 PM

> €500 in furniture

I feel like this is 3/4 of a coffee table?

by jawilson2

7/27/2026 at 9:16:58 PM

I purchased brand new furniture that looks pretty but quickly falls apart, looks horrible up close and isn’t comfortable. It’s basically decor pieces.

Amazon couch for $250:

https://www.amazon.com/Kingfun-Loveseat-Century-Upholstered-...

by retired

7/27/2026 at 3:01:41 PM

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

This is the latter.

See also "staging":

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

by throw0101d

7/27/2026 at 2:21:37 PM

Why is it written like that lmao

by saagarjha

7/27/2026 at 2:41:23 PM

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.

by Nzen

7/27/2026 at 2:29:43 PM

Its been "staged"

by blitzar

7/27/2026 at 7:54:21 PM

Actually in some places panels devalue a house because some people consider them an eyesore

by micromacrofoot

7/27/2026 at 9:58:18 PM

And to those people, clean panels devalue the property more than dirty?

by wodenokoto

7/27/2026 at 11:33:06 PM

all panels are bad regardless of cleanliness

by micromacrofoot

7/27/2026 at 8:14:56 PM

I believe this will pass as people get used to them as part of our modern world.

by g8oz

7/27/2026 at 8:42:02 PM

"people get used to them" is usually just old people dying

generally the markets where this happens have people who are too rich to care about electricity savings

by micromacrofoot

7/27/2026 at 3:12:12 PM

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

by Onavo

7/27/2026 at 4:18:08 PM

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

by gib444

7/27/2026 at 3:04:55 PM

[dead]

by aaron695

7/27/2026 at 2:19:45 PM

Re: the slightly strange shape of the curve. The drop at the beginning could be due to the matching between the panels getting worse. Solar panels in a bank don't like being in different conditions. As a rule of thumb they will all perform at about the same level as the worst in the bank but at the finer levels you could get less straightforward interactions.

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.

by rcxdude

7/27/2026 at 7:43:47 PM

> 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.

by lelanthran

7/27/2026 at 7:53:54 PM

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.

by Scoundreller

7/27/2026 at 6:46:48 PM

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.

by kurthr

7/27/2026 at 5:29:15 PM

I have a 19 year-old, roof mounted, 6.3 kW nominal system in two arrays (east/west facing), 40 deg. north. I've never washed the panels outside of rain and occasional hail storm "scrubbing". Replaced a failed inverter two years ago.

My peak summer output is basically the same as when installed, making 36-38 kWh on a cloudless day. I'm actually impressed my panels haven't really degraded in performance over those 19 years.

by tpoindex

7/27/2026 at 5:52:57 PM

That's really impressive and well built solar system, for it to last thta long. It shows how durable quality panels are. I have a 6 month old ~3.7kW system (6 panels in total), planning on installing another 6 very soon. My house is surrounded by trees so it's been a bit of a struggle in the winter.

by sgt

7/27/2026 at 6:19:28 PM

My latitude plus east/west arrays are a struggle anyway. On the best (presumably cloudless) December day, I got 13.98 kWh. My 12/1/2025 through 1/31/2026 average per day was 10.32 kWh.

by tpoindex

7/27/2026 at 7:50:44 PM

Panels should do 30 years, easy. Inverters will usually fail after 15y, and with batteries it’s unknown what the current gen will do - 15y, maybe 20? Definitely get LFP.

by manmal

7/27/2026 at 8:58:06 PM

I’m waiting to see what the sodium packs look like before we do Solar PV (it’s on the list but not near the top so no urgency yet).

by noir_lord

7/27/2026 at 9:58:00 PM

Sodium batteries are more grid scale I believe. They require seriously high temps to operate and thats best shared in massive banks

by malfist

7/27/2026 at 10:23:32 PM

Not just grid scale, already been used in EV’s, less temperature sensitive than Li-ion, way more charge cycles but not quite as energy dense as lithium per kg but that’s not a downside in a static installation.

by noir_lord

7/28/2026 at 6:29:38 AM

I've seen cheaper Chinese panels fail after less than 10 though.

by sgt

7/27/2026 at 5:37:48 PM

What the panels' technology / manufacturer?

by deepsun

7/27/2026 at 5:52:06 PM

SolarWorld, 175 watt, polycrystalline. I don't recall any model number (paper work is filed away somewhere.) ISTR mine were made in Germany. I think at the time my system was installed, there where some 225 watt panels available, but the 175 ones were a better price point per watt.

[edit - added technology]

by tpoindex

7/27/2026 at 6:50:39 PM

The SolarWorld company is no more :(

Which means your experience is irreplicable, other companies' solar panels may be crap.

by deepsun

7/27/2026 at 7:33:14 PM

Prices per watt of solar have fallen by so much over 20 years its absurd. You can probably buy the best and/or most costly residential panel on the market and still come well under whatever the median was 20 years ago. Probably well under a few standard deviations below the old median I'm guessing.

by asdff

7/27/2026 at 11:10:04 PM

looks like the planet is warming at the same rate your panels are decaying

by slim

7/27/2026 at 3:01:49 PM

Was just watching a video about a guy who has a boat that runs on solar power that he drove all the way from Finland to the Mediterranean in Winter. Obviously in the winter he was charging his batteries using shore power. But since spring he's been running on solar power doing long journeys and maxing out at 5-8 knots. He just cleaned his panels. Lots of salt, dust and sea gull shit. Also a few kids dropped a rock on one of his panels. Cleaning them improved performance by about 10%. Not nothing. But they were really dirty.

https://www.youtube.com/watch?v=FhBBUFuTwR4

by jillesvangurp

7/28/2026 at 2:49:35 AM

Yes, on a boat you have to wash the panels periodically to get rid of salt and bird poop.

The latter can be a surprisingly big problem. Southeast of Galapagos we had a booby sit on our spreader for a day, and it managed to cover our two 100Wp panels in the bow almost completely.

by bergie

7/27/2026 at 1:39:14 PM

It's a bit worrying the author is asking chatgpt about the tingle rather than making sure there's a grounding lug on all the panels and they're all bonded to a grounding rod.

The rudimentary nature of the setup makes me think there isn't something like a single conductor 12awg (or euro equivalent) copper wire that bonds to all panels and a basic $30 rod.

by walrus01

7/27/2026 at 2:02:28 PM

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.

by quickthrowman

7/27/2026 at 10:00:24 PM

I’m an electrical engineer. I just want to explain the hazard with panels.

They are DC, and the voltage is usually very high, between 300V and 600V.

At this voltage you will get a burn, like touching a hot kettle, but because it is DC you will be able to easily “untouch” it.

Yes, the panel frames should all be grounded to each other, and also to Earth in one spot along the chain, as this makes it more difficult to be electrocuted by them because the resistance of the grounding wire is much lower than the resistance of your body, and electricity takes the shortest path.

by aetherspawn

7/27/2026 at 10:46:27 PM

I was just pointing out that a solar installation with only an inverter and no transformer does not need a separate ground since it’s not a separately derived system. An auxiliary/supplementary ground rod is allowed by the NEC (250.54) but it is not required.

by quickthrowman

7/27/2026 at 3:07:37 PM

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

by amluto

7/27/2026 at 10:49:13 PM

> 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).

It’s not usually, all of the panels and also the metal racking must be bonded and grounded.

Supplementary grounds are allowed by the NEC, article 250.54

There are zero requirements for supplemental grounds, you could use a single 24AWG conductor bonded to a brad nail or a #6 bare copper conductor bonded to (3) 5/8” dia’ 10’ ground rods. The fact that there are no requirements should tell you something about the necessity of supplemental grounds.

> 250.54 Auxiliary Grounding Electrodes. One or more grounding electrodes shall be permitted to be connected to the equipment grounding conductors specified in 250.118 and shall not be required to comply with the electrode bonding requirements of 250.50 or 250.53(C) or the resistance requirements of 250.53(A)(2) Exception, but the earth shall not be used as an effective ground-fault current path as specified in 250.4(A)(5) and 250.4(B)(4).

by quickthrowman

7/28/2026 at 9:03:24 AM

The OP is pretty clearly not in the US and is not subject to the NEC.

And just because the NEC doesn’t say you need to mitigate touch potentials for a specific installation doesn’t mean that you shouldn’t. The NEC is just a bunch of requirements, not a complete guide to building safe, high quality electrical installations. And there appears to be plenty of guidance from IEEE about this if you feel like paying for a copy of the standard:

https://store.accuristech.com/ecia/products/preview/2085911

The NEC does have plenty to say about grounding for purposes of reducing potential differences in other (non-solar) installations, though. Swimming pools are a notable example (with no specific requirement IIRC to connect the fancy bonding to the Earth at the pool, but a typical concrete pool with NEC-mandated bonding is likely an excellent connection to the local soil).

Amusingly, an inspector could plausibly require an “equipotential plane” per NEC 547.44 if the solar array is accessible to livestock.

Alternatively, from first principles: suppose you are standing with bare feet on wet soil 100 meters from a building. That building has a very nice ground rod array, giving an impedance of 50 ohms from the building’s ground to your feet. Now take a long wire that is insulated except at the ends, connect one end to the building ground, and firmly hold the other end in your hand. How do you feel about this situation? You have a nice wire loop, potentially with area on the order of 100m^2, containing your heart. It can inductively couple to time-varying magnetic fields (e.g. the fields around nearby transmission lines) and it can capacitively couple to other conductors. It can resistively couple to power lines with multiply grounded neutral or to electrified railways or to nearby buildings with old-style (earlier NEC revisions) shared neutral/ground feeds And lightning can strike the array. I think it would be wise to ground the array to earth to reduce the potential difference between the frame and earth.

by amluto

7/27/2026 at 2:58:47 PM

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.

by tclancy

7/27/2026 at 4:52:42 PM

> a wash

Well done on this cleanly-executed pun.

by bityard

7/27/2026 at 5:12:45 PM

Took four open weight models to land it. And you are giving me way more credit than I am due.

by tclancy

7/27/2026 at 10:27:57 PM

This comment made me very sad

by vermilingua

7/27/2026 at 3:49:34 PM

Washing solar panels is one of the current popular business ideas on social media. It’s an easy pivot for anyone who already has some experience with much harder home repair handiwork involving a ladder.

The reason it’s popular is because most people don’t understand the economics at all. Someone can go door-to-door in a neighborhood offering to clean solar panels and making huge claims about improving efficiency so much that you can’t afford not to do it.

Homeowners who invested $30K in solar panels think of a $300-600 charge as an easy choice to keep their investment producing money.

My parents had someone going around their neighborhood trying to charge $50/panel for cleaning. They didn’t even climb a ladder. They sprayed washing solution from the ground. Most neighbors declined, but you could see the guy spraying down a couple roofs.

Easy way to clear $1000+ per day for knocking on some doors and pointing a hose at a couple rooftops, at least until the public figures out the scam.

by Aurornis

7/28/2026 at 7:25:04 PM

Many years ago (and possibly still today) there were firms offering refrigerator-cleaning services. Brushing off the condenser (external) coils.

Yes, that may save you a bit of energy. No, not that much, and overall the financial savings are a small fraction of the service's charge.

A friend worked in energy conservation at the time and actually studied the impact of cleaning coils on refrigerators as part of a recycling programme (so: measuring pre- and post-cleaning power consumption on units which had been in use, most for quite some time). The net results, over hundreds (if not more) units: to little difference to detect statistically.

If you're doing the work yourself or don't have to pay for it: possibly worthwhile for peace of mind if nothing else. Paying someone else? No.

I suspect a similar situation for solar panels.

by dredmorbius

7/28/2026 at 12:34:08 AM

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.

by ChiperSoft

7/27/2026 at 9:09:38 PM

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…

by rsynnott

7/27/2026 at 7:21:32 PM

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.

by jhot

7/28/2026 at 11:58:08 AM

$10/panel to go on top of a roof with the possibility of braking s leg or worse? I'll keep my coding job from my couch :O

by xandrius

7/27/2026 at 5:35:06 PM

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

by JamesSwift

7/28/2026 at 8:39:57 AM

Are window cleaners not a thing in your neck of the woods?

by benj111

7/27/2026 at 5:14:22 PM

Horses for courses. My system is off grid, so any extra power is just not used, and its designed in a way that a 2-5% change doesn't do anything. That might be a more meaningful change if I were selling power to other folks.

Kind of off topic, but I see a lot of folks proximate to me have built systems to turn panels so they face the sun more closely. I can see the use in that if you don't have much space or if you have a large commercial operation, but this area is very rural.

My array (4kw) which I built myself has 10 400W panels. The panels cost me $1200 because the minimum order is 12 and the supplier suggested buying extras; shipping large panels one at a time isn't cheap. In fact, the shipping for the entire system (about $5000 worth of equipment) was almost $1000.

But my feeling is that for the cost of a moving array that tracks the sun / time of year would have cost quite a lot more and have involved construction that I personally wasn't comfortable with. The conclusion I came to is that it would cost about the same to build a second array, angle it for "summer" (mine is angled to be most efficient in winter), and hook it to the other MPPT on my controller.

That would take up a lot of space, but a) I am 40 acres and b) then I could run a mig welder with impunity during the day...

by scarecrowbob

7/27/2026 at 6:37:07 PM

A lot of these designs are an artifact of a time when the panels themselves would have been far and away the most expensive component in the system. The place I'm in originally had 10 125W panels that probably cost north of $8k when installed, and they were mounted on a rotating, tilt-adjustable post. Also the entire house was wired to run off DC as much as possible, with three different wiring schemes throughout and rare & expensive appliances. It reminded me strongly of RV power schemes, and maintenance was probably a huge headache.

I replaced it all with 9kW worth of panels (about $3k, shipped) on 4 simple 60° ground mounts, normal wiring and appliances. Angle is optimized for early spring / late fall - there's effectively no sun in winter, and the rest of the year I have excess power even with fixed, sub-optimal angles.

The diminished cost of panels alone over the past 20 years has transformed "off-grid" from a pastime for wealthy hippies into a reasonable solution for remote living.

by Shog9

7/27/2026 at 8:25:43 PM

Ah, that makes a lot of sense.

by scarecrowbob

7/27/2026 at 5:17:55 PM

It does no longer pay to be clever with solar panels; they're too cheap. Angle not quite right? Add a couple extra. Summer vs. Winter? Add a couple extra.

by CapitalistCartr

7/27/2026 at 7:57:59 PM

> Summer vs winter, add a couple extra

My 6.7kW system produces 2.5 what we need in the summer, and 0.5 of what we need in the winter (even though its output here in New Mexico is relatively constant). Adding a couple extra is going to accomplish nothing in the face of a winter heating system (even with high efficiency heat pumps).

by PaulDavisThe1st

7/27/2026 at 5:21:12 PM

Except in germany where if you install too many you get classed as an energy company and have to pay extra tax. yay.

by cyberpunk

7/27/2026 at 5:38:53 PM

You don't get "classed as an energy company", you just have to pay taxes on the money you make from selling the energy. This starts at 30 kWp (up to that size, the income is tax free), which is very likely more than what you could put on a private home.

by filmor

7/27/2026 at 7:12:15 PM

well I mean okay, but it happened to me, and i had to pay a lot to an accountant to do this paperwork and i resent it utterly. I guess it’s unpopular here to be dissatisfied with the insane bullshit tax system in this country.

I didn’t make a profit, it’s not commercial — but apparently getting to almost break even on my energy bills is a “profit”.

by cyberpunk

7/27/2026 at 6:35:39 PM

Your post sounds like there is some strange rule regarding taxation of solar installations, but it is (or rather was) just treated as any other income from commercial operation.

- If you have any income from commercial operation (selling stuff) you are required to declare that, when doing your taxes.

- When selling electricity you're not so much classified as an energy company, but fall under similar taxation rules as a company. This also means you can get the VAT back, you paid when buying panels, inverters etc.

- Since 2023 solar installations smaller than 30 kWp are completely exempt from this taxation scheme. This means you're not paying any VAT, when buying equipment for your solar installations and don't have to declare the revenue.

- You can get around the 30 kWp limit under some circumstances by having multiple separate installations.

- Parent post is talking about an off-grid installation, which would be exempt anyway, because there is no revenue from selling electricity.

The tax exemption from 2023 was a very welcome move by SPD and the Green party to reduce bureaucracy regarding solar installations and I think the 30 kWp is pretty reasonable

Would be interesting to see, how other countries are handling this.

by majoe

7/27/2026 at 5:26:08 PM

even for the off grid system not connected to the grid?

by majso

7/27/2026 at 9:11:02 PM

Are these older systems? The panels are cheap now but they used to be quite expensive, which would’ve changed the economics a bit.

by rsynnott

7/27/2026 at 1:43:43 PM

Maybe the thing to do is to NOT upgrade existing working panels but rather set up a different/separate entity with completely different accounts and new panels?

And about the washing, I wonder if it would be worth it to automate the process with a spray of water periodically? 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?

by collabs

7/27/2026 at 1:52:28 PM

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.

by rjmunro

7/27/2026 at 2:03:54 PM

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.

by Tade0

7/27/2026 at 2:13:15 PM

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

by cestith

7/27/2026 at 2:20:12 PM

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.

by bradfa

7/27/2026 at 2:23:14 PM

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)

by rcxdude

7/27/2026 at 2:50:58 PM

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.

by bruce511

7/27/2026 at 2:39:20 PM

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

by kaelwd

7/29/2026 at 4:37:19 PM

If you can do that within your space constraints you’re probably right.

by cestith

7/27/2026 at 2:07:07 PM

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

by sluongng

7/27/2026 at 2:24:58 PM

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

by wongarsu

7/27/2026 at 2:19:49 PM

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.

by collabs

7/27/2026 at 4:04:37 PM

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.

by toast0

7/27/2026 at 1:57:17 PM

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.

by collabs

7/27/2026 at 4:33:52 PM

> 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.

by fckgw

7/27/2026 at 3:36:10 PM

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.

by conductr

7/27/2026 at 2:40:39 PM

Look at any outside surface in a rainy climate.

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

by BurningFrog

7/27/2026 at 1:48:09 PM

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

by ido

7/27/2026 at 1:44:11 PM

> If I increase the power output of the system then the additional capacity will not be eligible for the feed-in tariff and will revert to present-day prevailing tariff which is about 4x worse before you even consider that I currently get to use electricity and still get paid for generating it.

> This is the yin and yang of market-distorting incentives. Today's incentive to install solar becomes tomorrow's disincentive to upgrading it.

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

There are no subsidies in UK! Homeowners get so much money, because of all that sunshine and wind energy, their house generates! UK goverment just run out of money, when energy got expensive!

UK goverment needs to step up, to replace gaz with renewables!

You can not expect homeowners to sell energy bellow market price!

by bebe8393jrir

7/27/2026 at 2:00:22 PM

> 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).

by rjmunro

7/27/2026 at 1:52:28 PM

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.

by philipallstar

7/27/2026 at 2:00:26 PM

> 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.

by otherme123

7/27/2026 at 2:08:20 PM

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).

by hgomersall

7/27/2026 at 7:40:22 PM

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

At grid scale, yes.

For the house, not so much.

The feed in tariff was at one point 41 pence per kwhr which is probably £10 a day in summer.

but at 12p a kwhr it drops to £3.6

However, 10kwp of panels is ~£1800, but the micro inverters needed to drive them are >£3k (as its outside you can probably use two larger inverters.) Then mounting system is probably a good 800 quid too.

by KaiserPro

7/27/2026 at 2:49:51 PM

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.

by peter_stokes

7/27/2026 at 2:03:10 PM

Our peak daily export energy jumped by about 35%-40% when we had our panels cleaned for the first time in 8 years. They _look_ much cleaner, and the measured export shows it.

by hgomersall

7/27/2026 at 2:42:23 PM

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.

by trimethylpurine

7/27/2026 at 3:15:45 PM

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.

by hgomersall

7/27/2026 at 4:24:23 PM

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

When I check on the VRM portal it makes a difference, and since I am so dependent on them all year round, I have no problem giving them some attention from time to time. Ten mins well spent.

by CrzyLngPwd

7/27/2026 at 5:04:01 PM

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?

by scarecrowbob

7/27/2026 at 6:42:39 PM

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.

by CrzyLngPwd

7/27/2026 at 8:19:33 PM

> 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)

by Scoundreller

7/27/2026 at 11:02:25 PM

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.

by CrzyLngPwd

7/27/2026 at 8:30:06 PM

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

by scarecrowbob

7/27/2026 at 8:34:38 PM

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.

by scarecrowbob

7/27/2026 at 11:06:00 PM

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?

by CrzyLngPwd

7/28/2026 at 4:13:33 AM

True, I have learned a lot and that has been very interesting and quite fun. I'm at 6500' but am still planning on setting up an outside shower just because it's pretty here. I am waiting on that till I figure out an indoor situation, though.

I got a quote for a backhoe rental today and am a little apprehensive (it's by far the largest machine I will have operated), but hey, I get to run a backhoe for a weekend...

by scarecrowbob

7/27/2026 at 4:45:52 PM

> 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.

by jader201

7/27/2026 at 4:55:20 PM

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.

by bityard

7/27/2026 at 7:17:57 PM

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

by tensor

7/27/2026 at 4:56:16 PM

On tall roofs there tends to not be much dust.

by metadat

7/27/2026 at 6:43:33 PM

Mine are not on a roof.

by CrzyLngPwd

7/27/2026 at 5:45:09 PM

In the southeast states in the US, we experience "the pollening" each Spring, which can leave 1/8" or more of thick crusted pollen on solar panels. I wash ours at least monthly March through May. They're at least 15-20% more efficient, if not more, without the pollen crusted on them.

by nrjames

7/27/2026 at 2:28:58 PM

There’s this viral video on X of a guy at an Alex Hormozi talk saying he makes money cleaning solar panels… and it’ll probably turn into a whole market. If he’s getting 2% to 5% gains, I can already see marketing blowing that way out of proportion

by carloseduardopx

7/27/2026 at 1:41:39 PM

Appreciate the attempts to quantify it. I haven't tried to quantify washing, but I do look at mine regularly. I doubt anything accumulates that rain doesn't handle well enough.

Messing around with ground panels is lower risk and safer than roof panels where tool extenders and ladders start to become involved. If you have roof panels, you are the biggest danger to your panels (and yourself.) Don't try to clean them, spray them, knock snow off of them. I was told this multiple times by my installer. :)

by 1123581321

7/27/2026 at 1:59:21 PM

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.

by msdz

7/27/2026 at 3:24:33 PM

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

by 1123581321

7/27/2026 at 2:18:51 PM

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.

by varispeed

7/27/2026 at 2:58:39 PM

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”

by dd8601fn

7/27/2026 at 4:02:54 PM

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.

by marcosdumay

7/27/2026 at 4:13:27 PM

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...

by toast0

7/27/2026 at 4:48:23 PM

The regulations that tradespeople must obey and how they are contracted varies from one country to another.

by marcosdumay

7/27/2026 at 6:29:16 PM

And hopefully these independent contractors are insured. It may well be insurance requirements that limit the use of ladders.

by Crunchified

7/27/2026 at 5:03:52 PM

It would not surprise me if this was a law in Germany, for example.

by bityard

7/27/2026 at 5:52:14 PM

Stuff like this is why America continues to mog the rest of the world economically.

by Der_Einzige

7/27/2026 at 5:13:52 PM

Now I want solar panels merely so I have a reason to not have to clean my roof

by libria

7/27/2026 at 5:36:03 PM

Still the same leaves in the gutter, sadly, once they blow past the panels.

by 1123581321

7/27/2026 at 5:12:59 PM

> This is the yin and yang of market-distorting incentives. Today's incentive to install solar becomes tomorrow's disincentive to upgrading it.

Facing this as well. We've got our 5.2kW system in a pile in our yard as the house is being enlarged, new roof going on, etc. We're switching from a gas furnace to a heat pump system, and will also be installing a hot tub. I'm sure our annual power bill will double from say $1k to $2k, but it doesn't make sense to enlarge our system.

I'm 8 years into a 20 year net metering scheme (NEM2.0 in CA), and any changes I make will kick me off the plan. In theory I am allowed to add up to 10% or 1kW, but in practice my solar company keeps telling me it's not worthwhile. I think the paperwork and administrative burden of even adding the amount I'm "allowed" to add just means it's not cost-effective.

Whether or not the utility actually would notice that I'm mysteriously getting 1kW additional generation (if no paperwork was filed) is another story.

by rconti

7/27/2026 at 2:54:36 PM

So if it's a 2-5% increase, barely break even, it more than breaks even during an extended power failure if you live somewhere this is likely. There are a lot of things I choose to do to avoid future timelines where 'sus appliances break at the worst possible moment. This would be along the same lines to me. Your mindset may vary YMMV.

But if cash is tight, yeah, not so much.

by LogicFailsMe

7/27/2026 at 2:09:48 PM

Nobody can answer this. It simple depends on each setup. Some panels will get incredibly dirty quick like those in the south west where there may be a lack of rain and lots of dust but in other regions you may never need to.

by infecto

7/27/2026 at 3:51:31 PM

Of course washing them makes sense, physics-wise. As others have pointed out, you are almost certainly seeing a rise due to cooling off the panels (this would not make economic sense to do all of the time). Temperature has a pretty dramatic effect on solar panel output. Cooling a panel can boost production by 10% or more. Do not polish them. Solar panels are designed to be anti-reflective. You don't want a shiny surface.

But, the real factor in all of this is how valuable the time required to clean the panel is.

by kjjohnsen

7/28/2026 at 12:19:46 PM

I have worked in the solar industry, and "soiling" is highly dependent on soil, weather, proximity to roads, etc.

And I've seen cases where it made a 30% impact. In other locations, it is a non-issue, but vegetation was a hassle.

by lgcmo

7/27/2026 at 2:15:27 PM

Given the angle of a panel should match its latitude and average sun angle, the panels might generate noticeably more by being pitched steeper at over 30 degrees. Eyeballing this, it appears closer to 25 degrees right now which doesn't even make sense for the summer sun in the UK. I could be wrong as it also appears these are on a slope!

by z2

7/27/2026 at 4:01:39 PM

There are at least a couple of outfits claiming a nano coating or a nano glass surface for solar panels that are so smooth as to not collect dusts. Their other claim is greatly improved angular photon capture since the panel is just that flat. The two companies I've seen claim ~20% improvement - and less maintenance.

by ynac

7/27/2026 at 5:02:26 PM

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.)

by bityard

7/27/2026 at 5:07:21 PM

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.

by rconti

7/27/2026 at 8:11:53 PM

Dust can reduce capacity by 40% in the desert.

https://link.springer.com/article/10.1186/s40807-017-0043-y

by billbrown

7/27/2026 at 4:01:31 PM

If you feel "a tingle" when touching solar panels, that means there's a ground fault, a wiring short, or a missing ground wire. This is incredibly dangerous as solar arrays carry hundreds of volts.

by 0xbadcafebee

7/27/2026 at 8:42:18 PM

Last summer, I washed the single 220W module on the top of my campervan. It definitely improved the yield, but I suspect a vehicle can pick up a lot more dirt than a stationary install.

by jdblair

7/27/2026 at 5:31:24 PM

I'm surprised that the outcome was not much greater improvement. I'm glad though it removed one of my concerns about solar. I'm glad cleaning maintenance really is not really needed.

by citizenpaul

7/27/2026 at 9:22:15 PM

Are people really not aware that you have to wash your solar panels every few months? Your installer should have told you that much.

by jujube3

7/27/2026 at 3:04:14 PM

It totally depends on your area. In the PNW I get sap and conifer tree pollen all over my panels and have to wash them at least twice a year.

by turtlebits

7/27/2026 at 2:53:02 PM

I know that dust on the panels is one of the reasons that one of the Mars rovers eventually croaked.

by ChrisMarshallNY

7/27/2026 at 3:03:16 PM

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

by ButlerianJihad

7/27/2026 at 2:48:44 PM

I haven't noticed too much of a power increase in my backyard solar farm after cleaning, but I do notice a very significant increase by weeding the surrounding stuff. Even a pretty small amount of shade will very significantly reduce your yield, like seriously 20-30%.

Oh, also, I've noticed that at least with my panels, bird poop seems to be particularly bad. The dust that accrues doesn't seem to do much, but even a relatively small bit of bird poop will be almost as bad as weeds. Fortunately it's not terribly difficult to clean once it's dried.

by tombert

7/27/2026 at 5:18:25 PM

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.

by scarecrowbob

7/27/2026 at 2:17:15 PM

I imagine rain will clean them. In most places it rains every so often.

by ape4

7/27/2026 at 2:22:42 PM

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.

by mywittyname

7/27/2026 at 4:33:19 PM

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.

by coredog64

7/27/2026 at 2:18:22 PM

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

by namdnay

7/27/2026 at 2:53:51 PM

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

by left-struck

7/27/2026 at 2:40:37 PM

Definitely wash the panels.

However if you are using a string inverter you will want to wash all the ones on the same string in one go if you can, you don't really want them generating different voltage or you will miss out on a lot of power.

by jpgvm

7/27/2026 at 9:05:17 PM

it's simply common sense. of course cleaning them would make a difference....duh Talk about "overthinking"...nerds!

by bluehatman

7/27/2026 at 6:21:49 PM

Should we include this is the cost?

by dev_l1x_be

7/28/2026 at 1:42:37 AM

It depends.

In my mom's part of SoCal, it's extremely dusty. Without bi-annual cleaning a solar panel's output will drop by over 25%.

On the other hand, where my brother lives up in Norcal, an annual cleaning is overkill.

by gamblor956

7/27/2026 at 9:43:17 PM

I lose about 25% if I do not clean during bushfire season

by justatdotin

7/27/2026 at 5:09:17 PM

[dead]

by HumanAgent

7/27/2026 at 3:49:26 PM

Question for people here: my local power company charges a fee if solar is attached to the grid and is high enough to make installing residential solar impractical.

I'm thinking the best thing to do would be put a large battery in between the grid and my home and selectively recharge the battery with the solar. I believe that setup circumvents the fee since the only thing using energy is the battery, as though it were an off grid setup. I might consider not putting the entire home behind the battery but just the largest energy hogs, like the HVAC or others.

Does this make sense, are there existing setups like this and what are thoughts about something like this?

Thanks

by the_sleaze_

7/27/2026 at 4:40:22 PM

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.

by dgacmu

7/27/2026 at 5:06:16 PM

> 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.

by jaggederest

7/28/2026 at 1:45:40 PM

There are likely much lower requirements if your system is completely separated, though you'll still have to follow the general electrical code possibly including getting a professional electrician to build or certify it.

Some places don't even allow that, though.

by inigyou

7/27/2026 at 4:12:17 PM

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!

by 0xbadcafebee

7/27/2026 at 5:15:13 PM

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.

by sumtechguy

7/28/2026 at 1:47:11 PM

In that kind of situation you could work around this legally just by reconnecting loads to the other system as needed. E.g. battery is getting low, better unplug the fridge from the green-painted solar power outlet and plug it into the red-painted grid power outlet right next to it. You maintain the air-gap but still get to load-balance.

by inigyou

7/27/2026 at 3:52:24 PM

Ask a lawyer about the law.

by inigyou

7/27/2026 at 3:59:13 PM

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

by the_sleaze_

7/27/2026 at 4:45:01 PM

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

by sudobash1

7/27/2026 at 4:23:41 PM

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

by inigyou