Advice Needed - Panel Layout

Good Day Everybody

I am looking into putting up some panels in the “near” future.
The goal is to fit roughly 3000W in panels on the roof.
I have some shading to deal with, that will affect panel choice and layout.

What I have concidered this far is (6x510W) or (5x590W) to achieve my goal.
Im adding some photos, hoping for some advice on panel choice and layout based on the shading.

Thanks in Advance.

Photos are from July, I have less shade to deal with in summer.
Roof faces NE






Something to remember is that PV panels are sold as a peak power rate, but that is not what you normally get. All panels are like that.

As an example lets look at the ArtSolar 550W panel

The STC values is that wattage it is sold under and is measures in perfect factory conditions. It is used so you can compare vs the next panel and most manufacturers will use very similar test conditions, but this could be a bit different. Check the specs.

The NOCT is more the normal power you can expect every day use when the PV is mounted in the sun, hot and hopefully not to dusty.

So what to do with this information?
For safety calculations (wire thinkness, fuses, breakers, max voltage limits) you should use the STC values.
For usage requirements (how much panels you need to power your system) you should use the NOCT values.

I also have lost of shade in the winter that is out of my control. So I looked at half cell panels (144 half cells) and instead of using one bit MPPT with one or perhaps 2 trackers I went with smaller MPPT charge controllers each with their own tracker. Victron’s modular system makes this easy to do, but if you are looking at another system where the charge controllers are built into the inverter you might not have that opion.

your 11am and 1pm are going to be your big solar power times so I would put as many panels as you can fit in that bright spot.

I’d just chop down the palm trees. :grin:

and thats why the karoo is perfect :laughing:


My palm tree doesnt bug me much, the ones that are making the shade are 2 houses down and extremely tall

What system/brand are you planning to use?
Do you also have east/west facing roof and how is the sun looking on them?

Currently I have a kodak axpert mk2,
From another setup I helped a friend with I know the mppt likes to be at higher voltages.
Hence trying to get a single string of 5 to 6 panels as a start.
The idea would be to double that in the following year.
I am looking at Canadian Solar Panels at the moment.

House only has NE and SW facing roof space.
I would need to confirm what that side is like, i know there is shade in the morning, would need to do similar photos to see pattern throughout the day.

Focused on this side as I’m trying to get as close to north facing as I can

East and west facing panels worksvery well, but south will not work. You will have to use the north roof.
With the Axpert you will not be as flexable in your approach as I could be and for a high voltage string with 5-6 panels you will want them all in the sun. Any shade will limit the whole string. So see if you can optimise their placement as much as you can.

I think this is your least shaded area around midday

I think higher up on the roof is best. As the days get longer some of those shadows will fall off the roof (sort of speak). You will be better off with 1/2 cut cell as half the panel can be in shade and you will still get the other half worth of energy and a single string will perform better than if full cells. Better still one MPPT per panel however I suspect you will already be aware of this.

Sometimes optimising for winter is not the best for the whole year performance. I have east north and west facing panels. Due to a tall building immediately to my north my north roof is mostly in shade during the depths of winter. I place only four panels on my north facing roof in order to minimise the shade on the north panels. However if I had of placed more panels on the north facing roof they would more than make up for the winter losses in the six months that include summer. My north panels usually produce about 20-30% more than either east or west facing panels.

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Good day. I am fairly new no extremely new and mechanical the electrical side is a big struggle. Even the short wording takes me by a struggle also noting i am actually afrikaans. (Shoukd say enough)

Would this statement also be taking in consideration when using panels to plan the power.

I have Luxpower 5kw inverter and it can take two sets of panels of 3200w. Now at moment have china panels (long story why) 4 x 450w no shade on the roof and unable to reach 1,2kw on the best days just reaching 1,1kw and mostly under 1kw.

Should i then factor in for this 20 to 30% loss when planing the string. I need to power up in order to use less grid power.

The loss seems a little large… What is the tilt and orientation of your panels and load on the inverter? Those factors can have a big impact.


This might sound silly but I have seen multiple houses in my small town with this problem, are your panels actually pointing North-ish?
I have seen far too many South facing panels lately…

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OK, panels needs to point North, or at least in a northerly direction (North West or North East).

Should be angled upwards slightly, generally 25° to 30° depending on where you live. You want the sun to hit them perpendicularly at noon, but because of seasonal differences it will always be a few degrees off. One can look at noon whether the bottom lip of the panels throws a shadow behind or in front of the edge to get an idea.

When installed on an existing tiled roof, they are almost always angled a little lower than is optimum, but you accept the slight loss for the simpler and cleaner installation (and make up for it with a few more panels).

Must not be installed too close to the roof, or the heat trapped below them will basically kill production.

Finally, make sure the MPPT built into that inverter is an MPPT and not some PWM charger. It is normal for a PWM-charger to lose a third or more of the panel capacity.

If all is well, in South Africa you can expect at least 80% or so of the rating of the panel, because 1) we generally don’t get the full 1000Wm^2, and 2) our temperatures are far above the 25°C at which the panels are tested.

I would expect around 1400W from your modules around noon, if all is well.


Not sure about the angle on the roof. Will find out about that.

I will then make sure to get the angle more correct and same time use the opportunity to rais slightly from the roof to cool down. We are in Brits Northwest at it is more or less on the hot side here by us. The measurements was done at around 12h00 with the pool pump running and using grit power and solar then I know the solar is maxed out at about 1kw on the inverter and even on app when Iam at work checking most of the time.
I was scammed the panels has Canadian stickers but after removing them to test on the ground I saw the old sticker glue much bigger that the Canadian sticker. One of the 4 panels only gave me 3amps @ 43volts the rest of them 41v and just anout 10a but over 9a all 3 so i went to purchase another China panel which I tested befor purchase at flee market. Size was inspec with a 450w canadian. ( I understood from google that size does matter in panels) 9h00 in morning sun just out behind clouds got amost 11 a and just under 43v. After fiting it to my roof found it was 100mm longer that my pirate panels. So am planing on geting more of the last panel so that i have one string china brand and later get another string on the opposite sode of the roof as the side i am on gets morning sun so other side will give me afternoon sun. I just want to make sure that get most amount of panels in order te get the most watts from them in my system.

Ps. I had to redo al the wiring to the db as wires was mixed in size and alot was joints with insulation tape even die panels were cut and joined with tape. Al the joints was repaired with correct panel connections at thisstage

If you have your panels in a string and one of them is not producing, then that will limit the power of the hole string. It could be that one panel has a defect and then it would be better to replace that panel than to keep it in the string.

With A-grade panels you should get a report with the voltage and current that each panel produce under testing. These should be close to each panel you want to use in a string.

Yes for current, big NO for voltage.

You can never go above the voltage limits that your MPPT can handle. If the voltage is higher, then the smoke will come out and electronics don’t work without smoke. :no_smoking:
Most MPPTs will be able to limit the current if there is too much, so you can overspec on panels a little (10%-15% I would say if you are using good equipment). But normally when people overspec on their panels they underspac on their equipment quality and that is not a good combination. If you have the cheapest inverter/charger equipment, then it would be better to not over spec.
If you buy blue, then you should be fine.


Thank you for the info.

I know the panels is not a grade. But after purchasing the second clamp tester to measure amps. I removed panels from the roof to have the sun hit it perfectly bridging the positive and negative got good amp reading and volts. Almost as fake description on back of panel. Placing panels back on the roof as picture shown we tested again it was slightly later but amos went down from just over 10a and other one just under that to just over 5a on location.

I would think a internal problem would have been measured by bridging the panel. We did take the original one of the four out as it was only giving 3a where others was amlost 10a.

Luxpower shows max volts on each set @ max power open circuit 480v and the pv voltage range 120v to 385v dc so if i understand your previous comment this should not go to its limit but the watts might go about 10% over.

If you can walk on the roof without feeling like you might fall off, then it is probably around 15°. From here it looks like the typical tiled roof that’s somewhere between 15° and 20°. It is much better to add solar panels than to mess with the angle of the panels. It is safer too. The moment the panels are not at the same angle as the tiled roof, you technically need an engineer to approve that the roof can handle it (the additional lift created by wind), and those engineers cost enough to rather just add two extra panels.

Excellent observation. That may well be the issue.

Edit: Additional observation regarding the angle. The power it makes is proportional to cos(theta), where theta is the angle between the incoming light, and a line perpendicular to the solar module. cos(0) =1, of course, hitting it square on gives the best power. For small values of theta, there isn’t a very big difference. Which is another reason not to mess with the angle. Panels on a flat roof, however, shows a significant reduction in power, which is why I had to mention it.

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The panels i am hoping to have complete the one set on my roof is 47,62v open cuircuit volts and rated @450w so if Iuse 8 panels the volts would be @ 380,96 volts with in the sweet spot and less that the max of 480volts in the manual. The power will then be 3600w rated and the max on inverter is 3200w that would be about 12,5% over spec. Would this then work fine.

I am laughing now because everting made sense to me up to that point. I got lost there between maths period and first brake planing. That side didn’t treat me well in school. After reading that I was almost on my way to detention or to the principals office for net paying attention.

I understand alot ofthe rest. But from there. Sorry. No dice.