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I strongly recommend watching Dave’s entire video, it’s really extensive and interesting.

Notably while the N/S bifacial have an amazing showing in sunny winter day with ground snow (as well a significantly higher resilience against snowfalls), the year round testing he did shows that the performance crater in spring, with half the performance of standard inclined panels, and none of the morning / evening advantages of E/W bifacials.

In the end, the N/S verticals have a worse year round production than every other setup, and significantly worse than standard, but if you live in a location with a fair amount of winter snow and can swing (heh) it a tilting mount could be an interesting configuration for winter.

What if we do vertical bi-facial panels, mounted on a rotating circle that rotates to align the panels with the sun (north-south or east-east or in between) depending on the time of the year. Wouldn't that be the best of all worlds right now?

On a theoretical basis yes but a tracking array gets a lot more expensive, and a lot less reliable. The rotating circle also takes a huge amount of ground space.

If you put the panels in a diagonal (NW - SE), and you rotate each panel on its vertical axis, the need for space would be limited to a series of circles the diameter of the panel width.

No expert on the topic but surely a manually rotated system achieves the benefits of tracking without the overhead of installation and maintenance for an automatic system. As long as the panels are easily reverted to default position when no one can go and rotate them through the day (thinking domestic setup in the garden).

Plenty of people have gardens and land that is tended to multiple times through the day anyway (for gardening, animals, workshop activity etc).

> the need for space would be limited to a series of circles the diameter of the panel width.

Now your panels start shading one another.

Maybe I wasn't clear, but in the precise NS and WE configurations, there should be no shading.

As soon as you add moving parts to your setup costs and maintenance explode. It's usually better to just buy more panels instead.

Depending on where you live a system that allows to manually change the tilt of your pannels once per month could be nice. You get a free 5-15% boost, where I am in Europe the optimal yearly tilt is ~40 degrees, in peak winter the optimal tilt of ~70 degrees would shed snow much more easily.

You're right on motorized trackers though, way too complex and expensive to make sense for most people

> Depending on where you live a system that allows to manually change the tilt of your pannels once per month could be nice. You get a free 5-15% boost, where I am in Europe the optimal yearly tilt is ~40 degrees, in peak winter the optimal tilt of ~70 degrees would shed snow much more easily.

Yup, that's what I was referring to as a tilting mount in the original comment, a pivot and tracks to tilt the panels up/down to set them at whatever's optimal for your latitude and time period, or completely vertical if you're in a snow-heavy region.

The necessary engineering might not be worth it anyway, given current panel prices, unless space is a bit of a premium.

Moving parts? We're talking about something like a pipe that's a hotdog down hallway slip fit onto another pipe here. With zero maintenance that will still have a service life that exceeds several generations of panel.

Plus at least one motor plus sun tracking controller. All of that has to operate 24/7, all year.

Depending on your local climate, that has to be sun and rain proof. (Most Nema 7 "3D printer" motors are not waterproof... Ask me now I know )

Nothing a quick hack job can't solve for you, but if you want to sell it (and make sure your customers will be satisfied for decades) it quickly adds up in price.

You don't need a motor. You need a recurring calendar reminder to send someone out there to spin them all 2x per year at whatever day you determine to be the ideal crossover point where you want to switch between NS and EW.

The panels can be stayed in their correct positions by a trash tire or whatever buried in the ground with two chains poking out to clip to the panel corner.

None of this is rocket science. This is all stuff that has been proven out over the past 200yr of fence and gate construction.

Similar could be used for changing between tilted and vertical though you'd need more material.

Panels have warranties of 25 years.

A pipe on a pipe will last close to 100 if you don't screw up the details...

vertical panels also kinda work as fences and aren't that much more expensive (actually might be cheaper...)

This. I am seeing this more in Austria and makes sense since a solar panel is really one of the most mass produced fence panel size things in the world. By choosing them you are also guaranteed replacement panels in the same dimensions compared to buying some random fence panel

Over the long term, there might be less wear and maintenance on either configuration. I'm guessing the vertical panels wins there.

The anti-duck-curve is actually really, really pronounced for east-west mounted bifacial panels.

The panels still don't generate any electricity at night of course, but other than that the output is an almost perfect inverse of the conventional equator-facing angled mounted panel output.

Just search for "bifacial solar panels graph".

Just to be clear, this is only advantageous when compared to fixed solar panels, not solar tracking ones correct?

Absolutely but tracking is expensive relative to just throwing more panels at the problem.

But shading is also a factor. If you want to get unobstructed sun across the whole day, you need to be built on a nice curve of a hill? Or build just a straight line of panels?

Depends on what you mean by advantageous. Solar tracking setups are very expensive relative to a fixed panel one. They can produce more power per square meter via higher utilization but cost so much it makes more sense to just buy more panels if you have the space.

I meant advantageous in that the anti-duck-curve of these panels would only be superior compared to the duck curve of a fixed panel. But that it would be inferior compared to the (what I presume is) the very high peak of the regular-duck-curve of a traditional solar tracking panel, since the "tails" of the curve should be similar at sunrise/sunset. But I see now that solar tracking seems to have fallen out of favor due to the economics of how cheap panels are.

The economics changed, it is now cheaper to put more panels East/West than having tracking ones as the tracking hardware is expensive. The tracking panels have the advantage to be put vertically in case of heavy hail.

My next array is likely to be east-west vertical bifacials, as I need only a small amount of additional capacity in the summer, but could still do more in the winter.

We currently have:

- summer optimised array: almost flat, 15 degree, optimised for maximum power on sunny summer days, mostly runs our cooling

- winter/morning array. Points SSE, 65 degree incline. Gets great energy in the mornings, and on winter mornings. Performs surprisingly well in overcast conditions. Generates about the same power in midwinter and midsummer.

- winter/afternoon array. Same as the above, but SSW.

18kW total faceplate capacity, in reality we peak at around 5kW, but have that for about six hours of the day for 9 months of the year. Also means I can run three arrays on two MPPTs as the two tilted arrays are basically mutually exclusive as to when they make power.

The other reason for leaning towards vertical panels is cleaning. The flat panels accumulate a crust of crap (pollen, soot, dust) that cements on there fast, and requires vigorous scrubbing to remove. Kills 20% of the capacity unless I get up there with a broom every six weeks. The 65 degree ones I have not had to clean once, as stuff just slides off them.

That, and a pallet of bifacials is now cheaper than a pallet of monofacials.

Not having snow accumulate on the panels definitely will be contributing to that gain since a bunch is lost on more horizontal panels in those parts of the world due to a layer of snow sitting on top for quite some time after the event.

One big trade off/risk is a large vertical panel essentially becomes a sail in high winds.

4. they can be setup in places where flat-mounted panels are not an option, like agriculturally used fields. Veritcal pannels allow livestock and/or food production on those areas, while preserving access for tractors and machinery.

A vertical panel has infinite higher efficiency that a flat-mounted one, if a flat-mounted one couldn't be constructed due to floor requirements.

Even a vertical panel will sweep shadows across the fields. Many vertical panels sweeping many shadows will probably affect many types of agriculture.

> Many vertical panels sweeping many shadows will probably affect many types of agriculture

yes, and sometimes it's a positive effect.

source is e.g. https://theconversation.com/how-shading-crops-with-solar-pan...

A lot of crops actually yield better in partial shade and are grown in open fields as shading is more expensive than the yield penalty.

Unless you're planting energy crops like corn or canola, that aspect tends to be still net-positive even if perhaps a bit of the solar yield has to pay off a minor reduction in crop yield.

Notably though grazing pasture mostly doesn't complain and if mounted suitably (IIUC low enough density and high enough start above the ground), it can co-exist with effective nature preserves.

this is an instantiation of my favorite problem-solving maxim that I learned in spirit as a boy scout: "Doing something suboptimal is almost always better than not doing something optimal." When my scoutmaster said it it had a few more four letter words and smelled like cherry brandy, but it was still true.

Only at lower latitudes. In the high north, the better config is vertical but one-sided in a V pointing south. Ideally then, one panel is face-on during the long sunrise, the other during the long sunset. Compare to at the equator where one side of a two-sided panel is facing the sunset/rise.

This opens the interesting prospect of hinged vertical pannels that could be adjusted for the season, opening up the V in winter and closing it in summer

Bifacial panels are almost as cheap as single panels though, at least when I look at clearance panels. Does that affect which is better?

The one gotcha is that roof mounting for vertical is a bit of a headache & the structural support is often precisely the wrong way round.

This is an interesting application; it sounds like they've worked through a bunch of those issues: https://cleantechnica.com/2025/09/27/bifacial-rooftop-vertic...

Interesting that they list wind as one of the places where vertical panels have the advantage - my intuition would have been the other way around, with angled panels doing better in windy conditions. Wind uplift isn't something I'd have even thought about.

I meant more on a classic home with an A-frame like roof.

Don't think it's a coincidence that the demo vid they're showing off is a flat factory roof

Yeah, I mean the peak of such a roof is the only practical place for it. I'd say this style of mounting is simply not appropriate for all types of roofs, and that's not exactly a bad thing, just geometry

Yeah, and the mounting would need to be robust enough to withstand the panels acting like a sail in storm winds.

I think it'd be interesting to look at how these might be colocated with crops.

Instead of mounting on a roof, maybe this should be used in place of fences.

One thing Jenny Chase (longtime solar analyst with Bloomberg) likes to point out is that in many places, solar panels are actually cheaper than fencing materials [1]

1. https://www.ted.com/talks/jenny_chase_solar_energy_is_even_c...

How they hold up to kid’s soccer balls tho?

When I bought my solar panels, they showed me their test video of launching balls at them to simulate hail. They said you're toast if it gets to baseball size but below that you should be fine.

Unfortunately, she doesn't say what kind of fence she's talking about. The kind of fancy privacy fence people put up between yards, maybe; but I'd be impressed if they're cheaper than livestock fence, which is the context some people are talking about in this thread. A typical cattle fence (woven wire, steel posts, barbed wire on top) will cost about $2500 per quarter-mile right now for the materials.

I'm not sure what a quarter-mile of solar panels four feet high would cost, or whether they'd survive the occasional cow rubbing on them. Neat idea, though.

Can they be used in apartment. We don't have roof space but can hang them vertically from balcony. Bi-facial won't work but what about mono-facial?

Germany allows apartment tenants to hang panels on their balcony and feed 800W for their needs.

https://www.canarymedia.com/articles/solar/how-germany-outfi...

Utah also.

https://diysolarforum.com/threads/plug-in-balcony-solar-beco...

Assuming they can’t/won’t/shouldn’t back feed, that’s a lot easier to do in most of 240V single phase land. In US/Canada, you gotta pick the side of your building’s circuit that your continuous loads are usually on.

I don't understand what's different...

We're only talking ~800W 120V in most cases, so phase balancing is immaterial in this use case (in the context of balcony solar).

Edit: For larger installs (many vertical panels, >1kw), agree that balancing and a dedicated circuit is likely more optimal.

I mean, if you can't backfeed, you might have stuff "on" in your home, but your solar might not be on that side so it's not doing you any good.

What a bizarre situation. So if you have extra balcony space, you are not allowed to generate more than 800W for your own use?

Perhaps it is an arbitrary limit picked out of concern for weight and / or live energy in a place normally meant as living quarters. Too much of either on a balcony would be a hazard, especially if everyone with a balcony was doing it simultaneously in buildings not really built with either in mind.

800w sounds low to me, especially on 120v in the US, but the rules may have been in place for older less efficient / bulkier panels in mind.

Mind you higher powers just need a licensed electrician to sign off and usually also have them permanently wire it in as those setups won't need an AC side plug so the costs of essentially a generator hookup over a fixed tie-in isn't worth it, and they require notifying the local grid. Might be that beyond 10kWp the grid can tell you sorry-capacity-not-ready (but the grid will have to fix that soon, there are rules) but yeah.

This is complicated legalese. "For your own use" doesn't technical exist, you are outputting your solar production into the main grid - and this is capped at 800W for grid (and house installation) safety and stability issues. You need a meter that can run backwards, but you have the right to demand from your electricity provider that they install one.

Bypassing the grid and using your own storage infrastructure is AFAIK not allowed in Germany (there are heavy taxes on electricity, that you would be omitting - similar as to how you technically are not allowed to make your own Schnaps at home due to taxing).

Last I read them, electricity tax was only applicable for sale and certain situations that involve transferring power across parcel/plot boundaries. An entity is allowed to generate it's own local solar power for own local consumption, and for that it's perfectly fine to rent/lease the equipment/panels but you can't just tax-free buy electricity itself outside some limited situations that are to allow e.g. an apartment tower to use solar panels as cladding to then sell the power to the tenants instead of forcing every tenant to lease their own electrically independent section of the facade.

You need me, an electrician, for bigger installation. 800W can be done by everyone and doesn’t require registration to grid operator and tests. Some people don’t mind having illegal 1600-2000W installations, never heard, that someone got fined for that. Generated energy (if not consumed) is not paid for anyway.

I think it's the plug-in part that is limiting the power. Most of these sets you just plug in to a existing outlet, not wired into the electricity panel. Feeding in 800 watt directly into the circuit allows you to draw more than the rated 16A 230 volt from that circuit without tripping the breaker. The ~20A you can manage this way is probably within safety margins of most installations.

Germany is a litigious country, with most of the things insured.

If people started plugging a 2kW grid tied inverter in a normal power socket - as is the case for balkonkraftwerk - houses would start catching on fire.

Nobody wants that. Yes, regulations are necessary for a safe and civil life.

You're not allowed to burn down "your" apartment building, because you didn't understand that its wiring was not designed for the extra load, or that overloaded wires get very hot.

If you have a south (or SE or SW) facing wall without much shadowing from nearby buildings or trees, vertikal mounting does work OK. Do not expect to reach the panel's nominal Wp rating though, output will peak at 50-70% of that. But panels are cheap - if there's enough room, just overprovision twofold. Just take care to buy an inverter that is OK with such a bigger configuration. And vertically mounted panels will generate more power off-season than tilted ones.

How well does a biphasic panel work mounted vertically on a light coloured wall at least a meter+ away (depending on panel size) ?

Just clad the wall between the windows (if any) in panels? Eases the wind loading that way as wind can't really get behind them anymore.

Think of them as (glass) fence panels with a convenient mounting frame. Just respect their dislike for partial shading from objects that are "near" (cast a hard shadow with wel defined borders relative to the cell/grid size on the panel), and it'll be fine. If they are arranged to have substantially different sun intensity and/or timing, run them through separate MPPTs or use "power optimizers" that do the same effort but without requiring more wires back to central than the simple "one single string of panels" has.

Due to recent issues out there: calculate worst winter peak voltage and make sure there's a healthy margin to the peak allowed safe/no-damage input voltage to the MPPT/charge-controller/inverter.

Panels eat less of their own current at any given operating voltage, the colder they are. And winter mornings after soaking in night cold are worst case conditions for that as they had no time to heat up yet for the first minutes past sunrise.

> 1. In places with high-albedo snowy winters, this arrangement can boost winter production, which if you have snow, tends to be the energy-heavy time of year.

I guess you also don't need to remove the snow from the panels?

Living north western Europe, a good chunk of the year the sun is basically only coming from the side most of the day (nightmare for driving btw).

This might work a lot better.

Vertical also doesn't take up very much real estate.

if you put up just one row and don't mind the shadow

You mean like a privacy fence?

Sort of, but if you use it as a fence you'd need to ensure nothing casts shadow on it.

It's more that you have to manage shading to happen in a way that the module's structure and your array-combining wiring/circuit effectively contain the shading impact to be closer to proportional to the overall shaded area than to causing more catastrophic loss (an individual solar cell in a module will be wired/biased as a blocking diode that's merely photoconductive from the limited light it receives unless bypass diodes are integrated into the module). E.g., usage of power optimizers, modules/panels with cell&bypass-diode arrangements that work to effectively target and mitigate the shading patterns you experience (e.g. a wall getting shaded when the sun sets below the horizon formed by neighbor's roofs), and such.

Partial-shading-tolerance designed modern panels will quite happily tank partial shading, and as long as you keep the shading aligned in the design direction of the panel you will have within ~30% of the usual efficiency (i.e., still like 14% instead of the usual 20%) relative to the remaining irradiation that your panel is still receiving after the shading took it's chunk.

Just take care to ensure the shading conditions for all panels that are passively combined into an array are sufficiently same, or at least behave in a way that the modules can bypass effectively to not loose an unshaded panel's yield due to one panel in the group having some shade on it.