# Can I face solar panels North, East and West?

It’s a solar panel design question I pose to almost every electrician and solar salesman I interview: “Can we install solar panels without optimisers on three different orientations?” Nine out of ten times, their answer is wrong.

To explain the answer, I’ll go back to the basics with the power formula. Next, I’ll explain how we design solar panel systems both in series and in parallel, and how this affects voltage and current. Then I’ll show how, with a standard string inverter, we can install solar panels in more than two orientations. Finally, we’ll consider some things we should avoid when paralleling east and west, and more efficient options that are available in these situations.

## Lesson #1: Power = volts × current.

Watts, volts, amps, power, current. You may be familiar with all these terms but might be uncertain about how they relate to one another. I’m going to explain these terms with the water pipe analogy. (The way I explain it is simplified – it’s not a perfect analogy.)

• Current is similar to the size of the water pipe. The bigger the pipe, the more water can flow.  We measure current in Amps (I).
• Volts is like the water pressure on the street or the pressure behind the water pipe. In Australia, that “pressure” for electricity is 240 volts (V).
• Power (P) is the result of the two. A fire hose has a lot of power because it’s a big hose flowing at high pressure. We measure power in Watts (W).

There are three ways we can write the formula; all mean the same thing.

You can use this basic formula with household appliances.

A 2400W kettle plugs into a 240v powerpoint. How much current does it draw?
2400W = 240v × 10A

Or use it for solar design:

A single solar panel is operating voltage is 30V and 8amps. How much power is it producing?
240W = 30V × 8A

## Lesson #2: Voltage is added in series

When we design a solar panel system on a roof, we generally connect them in”strings”. A string is a group of panels (usually between 5 and 13 panels) “daisy chained” together – or more correctly connected in series.

In this diagram, we have seven solar panels strung together in series. One panel (with reasonable sunshine) produces 8amps and 30 volts. As mentioned earlier, that one solar panel will produce: 30V x 8A =240W.

When we combine the seven solar panels, we have 210v but still only 8amps.
210v x 8a = 1680 W.

Note that the voltage is added in series, the current remains the same.

## Lesson #3: Current is added in parallel

When we parallel two of these strings, instead of adding the parallel voltages together, we add the current together, and end up with 210 Volts and 16 amps,

210v x 16a = 3360W

This time the current is added in parallel, the voltage remains the same.

## Lesson # 4: Solar panel design on a simple roof

Now let’s design the parallel string of 7 solar panels and the single string of 7 panels on the roof. To make the job simple, we’ll first choose a big house with a solar-friendly roof.

Most string inverters have two separate inputs called Maximum Power Point Trackers or MPPT’s.  As the sun’s intensity and angle on the solar panel changes during the day, the MPPT continually “Tracks” and adjusts the voltage and current to find the “Point” where it can achieve the “Maximum Power”.

Notice how each string of solar panels is facing the same orientation. We have one string of eight panels facing North, and two strings of eight panels parallelled into the other tracker facing east.

But let’s get back to reality. Not every roof is so solar panel design friendly. Let’s look at what happens if your roof is more limited for space.

## Lesson # 5: A series string of solar panels must face the same direction

This one is straight out of the Australian Standards.

PV modules that are electrically in the same string shall be all in the same orientation within ±5 (azimuth and tilt angle).
ASNZ 5033 clause 2.1.6

There is a good reason for this. Current flowing through a string of solar panels is limited to the weakest panel just like water flowing in a hose is limited by a kink in a hose.

This example shows a series string of six panels, three panels facing east and three facing west. In the morning, the eastern panels would be dragged down by the west. Then in the afternoon the western panels would be dragged down by the east.

(As a side note, we could not parallel these panels, as a string of 3 will only run at around 90 volts, which is too low for most inverters. In this case, we would need to use optimisers).

## Lesson 6:  The Myth, Parallel strings must face the same direction

Here’s where many solar electricians and solar salespeople get unstuck with a solar design. They know that all panels in a string must face the same direction, but then they assume all the panels connected to one MPPT must face the same direction.

If we apply the knowledge we have so far; it seems to make sense. We face series panels in different orientations because the panels that run at a lower current will act like a kink in the hose.

The idea then is that we also cannot design parallel panels to face different orientations, because the panels that run at a lower voltage will drag down the panels that run at a higher voltage.

But, it turns out, working within inverter input current limitations, we can!

Solar panel design East-West on 1 MPPT

You may know enough about you household electricity to know that runs at 240volts. This figure is relatively constant, in fact by regulation it can be should sit between 220 volts and 253 volts. So when you are using more power at home, it is not because the voltage is changing – it is the current that is changing.

Now back to solar panels. When the inverter first turns on in the morning, each solar panel operates at about 30 volts and 0.1 of an amp. As the sun comes up in increases to 2amps, then 3amps and until it reaches it’s maximum of around eight amps at full sun. The voltage, however, remains about the same: around 30 Volts.

Below is Fronius monitoring data of an east-west system we installed last year. Because we did not need to parallel this job, we have the voltage data of the east and west array running on separate MPPTs.

The Blue line shows the power increased during the morning. For simplicity, I haven’t displayed current it in this image, but it follows the blue power curve. While the two DC voltages don’t perfectly match, they remain similar – usually within 5 percent of 350 volts. If this solar panel design was with two strings to only one MPPT, then the MPT would adjust the voltage to the point that would allow the most power to be produced out of the two strings.

Note, there was a point in the morning when the purple line drops off. This is the western panels that were producing very little power. If both the east and west panels were on 1 MPPT, the voltage would have remained high, and losses on the western array would still have been minimal.

## How much efficiency is lost?

In 2012, a case study by Fronius showed how installing east-west panels on 1 MPPT caused losses of less than 1 percent compared to using two inverters / 2MPPTs. This case study is admittedly outdated as the inverters that were used were less efficient than inverters available today. The actual amount of  efficiency loss will depend on several factors:

• Orientations only 90 degrees apart will cause less voltage variance and less loss.
• Solar panel design on flatter roofs will cause less loss.
• Installing one array in the shade will cause significantly more losses on the other array and should be avoided.
• The inverter’s optimal power and voltage efficiency curves.

However, in the right situation, splitting panels east and west on 1 MPPT can be a cost-effective way of installing a larger system on your roof.

If your roof line dictates it, or if increased cost is not a concern, Module Level Power Electronics may be a better option. MPLE allows every panel to run independently of each other, regardless of orientation or shade. Here are the options available:

Just as a ballpark, a 6.6kW optimised solution can cost you about \$1000 more than a standard Fronius non-optimised system.
If you are in South East Queensland, we’d be happy to advise on a solar panel design that would best suit your home.

## Conclusion

When designing solar, (without optimisation) installing a series string of panels in two different orientations will cause significant power loss. For this reason, AS5033 does not allow it. However, running two parallel strings of panels in different orientations will only affect the voltage slightly, so power loss will often be minimal. As a result, a solar panel design on 3 different orientations with a dual MPPT inverter will cause minimal power loss. We take factors such as shading, pitch, and inverter efficiency curves into account, and in some situation, we recommend using optimisers.

For further reading on basic solar design, read my post:  What’s the best direction to face solar panels.

### 40 Comments on Solar Panel Design : North-East-West

Elliot said : Guest Report 2 years ago

Hi Paul. Yes, you are correct that the same theory works for North and East Orientations. Given the panel numbers you're talking about, an option that might be suitable for you could be one of the 3 input inverters currently on the market. Goodwe make one that has a very good reputation in the industry. We are currently testing it and the results so far are very promising. Be sure to look out for Marks review of it in the coming months.

Paul said : Guest Report 3 years ago

HI Mark, Very interesting post, sadly I'm in NSW. I have an ugly roof line that results in 2/3 of my panels facing west and 1/3 north. I'm assuming the same theory works by using the parallel lines in north+east directions. However I can only fit half as many panels on the east as I can on the north. From what I understand the parallel strings must contain equal number of panels. Would the Tigo Retrofit Optimzer TS4-A-O fix this situation so I can utilise the east side or is it too big a difference for the parallel lines? There is also the potential issue the roof line may cause shadows on the east by mid afternoon. I would greatly appreciate your thoughts.

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Mark C said : administrator Report 4 years ago

Hi Krrish. Sorry for a delayed reply and I hope you haven't installed yet. That sounds like an expensive way to use a more affordable but inflexible inverter. I would try to stick with 1 inverter that can handle parallel input (Fronius). Then use larger panels and have even strings paralleled into one tracker. Should cost similar with a better result. Only use Tigo if absolutely necessary. It's a weak point in the system.

Krrish said : Guest Report 4 years ago

Hi Mark, Thanks for the great and enlightening post. It covers almost all aspects of Solar and is a must read. I have a quick question and need your advise: I have limited roof space on my North and West roof but have more space on my East roof but on two different levels (tiers) and my Solar installer has suggested the below: 6 x Qcell Duo G5 panels on East roof on the lower level roof 8 x Qcell Duo G5 panels on East roof on the higher level roof These 2 to be connected to 2 different MPPT on a Sungrow 5 KW inverter 6 x Qcell Duo G5 330 panels on West roof 4 x Qcell Duo G5 330 panels on North roof These 2 to be connected to 2 different MPPT on second Sungrow 3 KW inverter I am keen on getting a 3 MPPT 8KW inverter and using Tigo optimizers for the North facing panels but it seems too pricey. Need your expert guidance.

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Danny said : Guest Report 4 years ago

Hi Mark, really appreciate all your posts. I would like to ask your opinion on a 6.6 kw system consisting of 20 x 330 w q cells with 10 facing north, 5 east and 5 west. I have minor / moderate shading on the west and looking to use 5 kw SMA Inverter (single phase). I lean towards the SMA for the lower operational noise over other inverters. Another installer say I must go with Enphase as the 5 eastern panels won’t produce enough voltage to start the inverter ? and that I can’t have 2 orientations into 1 mmpt. Any feed would be appreciated. Sure wish you operating in NSW !

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Mark C said : administrator Report 4 years ago

Hi Jonothon, Strings have to be equal numbers if you parallel them (I'm pretty sure that's in AS5033). Also, a string of 5 would be fairly short for the efficiency of the inverter. One way to do it would be to use Tigos on the 5 and 7, and string them in series.

Jonathon Dempsey said : Guest Report 4 years ago

Hi Mark, Thanks for all your info it's great to read. I am a CEC accredited installer, (I am only quite new to this). I am wanting to install 5 panels on my north roof, 7 on my East and 8 on my West. Shading isn't an issue except very early and late. Will it matter which two strings I parallel into 1 MPPT? Do I have to do East and West and do they have to be an even number of panels? Or can I do East and North? Would I need to use optimizers? Cheers.

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Mark C said : administrator Report 4 years ago

Hi Marcin, SolarEdge isn't an option. Even if it were reliable, this would be a bad design for SE. If you use Fronius, you will be running your voltages very low. It may only need three panels to operate, but at that voltage and power, it will run really inefficiently. In my mind, there is only 1 decent solution - Enphase. And it should not be too expensive (compared to putting Tigo's on every panel.) So here is my advice - option 1, get 320W panels with IQ7 micros. Only put them in the better locations if your budget is tight. Even better, get SunPower 360W panels with IQ7X micros. Having high wattage panels is the most important thing when dealing with small shaded roofs, and Enphase is cost-effective when dealing with smaller systems and higher wattage panels. Enphase will also be more efficient and produce more power on this type of roof.

Marcin said : Guest Report 4 years ago

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Mark C said : administrator Report 4 years ago

Hi Derrik, Timely question. I just got back from visiting both Tigo and Enphase in Silicone valley. Short of a long answer is I would be banking on Enphase. Expect at minimum a 5 per cent chance that one of your Micros will fail in 10 years - but if you have shade issues, the monitoring that Enphase offers as standard is the best option.

Derrick said : Guest Report 4 years ago

Hey Mark. Thanks for your articles. They are high quality and informative. I've been struggling a bit to find the best set up for my home and hope you can help me. My house faces south. I plan to have Solar panels on the North, East & West roof. The problem is I have a tall pole 14m to the north of my roof line. The height is 27m. At Latitude 36deg S, I calculated that it will cast a moving shadow across all my panels 6 months of the year. I figured I'd have to get Tigo or Enphase. Which set up would generate the most power? Thanks in advance for your help.

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Mark C said : administrator Report 4 years ago

Hi George. As much as I like tigo, avoid rooftop power electronics if you can. Can you justify higher wattage panels like 330 Qcells or 360 Sunpower? if not, go Tigo.

Mark C said : administrator Report 4 years ago

Hi George. Only use Tigo in shade, or if you need to do one STRING of panels in multiple orientations. And, my tests on panels is really outdated. If you want my advice now, go with QCells or Canadian. My advice these days is better researched than it was when I wrote that post :)

Mark C said : administrator Report 4 years ago

Hi Richie. If you have limited roof space, install higher wattage panels. We use Qcells 330 (and Sunpower 360W panels). Then you only need 20 (or 18 panels) and you can install 8, 6 and 6. Definitely install Fronius. ABB still need to get their act together, actually they have sold their inverter company to Fimir and the transition happens next year.

Mark C said : administrator Report 4 years ago

Hi Steven. By Australian standards, you can't do this, so I haven't tested it. But, in theory, it would mean the panels would have to run at the same voltage, so the longer string would be dragged down to the voltage of the shorter one. Effectively it will produce the same or worse than parallel 6.

Steven said : Guest Report 4 years ago

Hey Mark, Great post :) Questions Please: 1. I agree with the science and maths- sounds great. There fore- there should be no problem also installing North and West facing strings in parallel as well on the same MMPT? 2. As voltage is only added in series, what would happen if you had a different number of panels installed on the East vs West string? So say 6 on the East and 7 on the west. If this is possible, is the total voltage for that MPPT a median of them both? Thanks in advance, Steven

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Steven Hord said : Guest Report 4 years ago

Thanks again Mark for such an informative post :) Blessings Bro!

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Richie Nicholas said : Guest Report 4 years ago

Hi Mark, Thanks for taking the time to explain this in detail. I am contemplating upgrading from a 2.2kW system with panels facing east and west as our consumption has increased. I am looking at a 6.6kW in 315Wpanels with a 5kW inverter. My north facing roof is small and can probably accommodate 8 panels, this leaves 7 panels east and 6 panels west. What would be the ideal way to wire this up and /or is there any sense in having the panels facing N-E-W? Any suggestions for inverters ABB/Fronius? Thanks in advance.

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George said : Guest Report 4 years ago

Mark Thanks for the response regarding the east, west and north setup just adding to this would using Tigo Optimizers be advisable or just wasting money? Also looking at using Risen solar panels after reading you test results or do you think there is a better option regarding value for money? Cheers George

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George said : Guest Report 4 years ago

Hi Mark Thanks for that info it's really helpful, just one last question is it worth putting on Tigo Optimizers with this system with it being east, west and the 2 norths or would that be a waste of money? Cheers George

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Mark C said : administrator Report 4 years ago

Hi George. Interesting. The installers are wrong and this is the reason I wrote this blog. The 6 and 6 panels you tilted north should be paralleled like the east/west diagram (because of the 20 degrees east/west separation.) These panels go into 1 input of the inverter.

George said : Guest Report 4 years ago

Hi Mark, I am looking at the option of installing a east,west and north facing solar system on my shed roof that has low pitch of around 10 degrees. I understand how the east, west setup works but I am wondering about the north. There would be 6 facing north on tilts with a west incline and 6 facing north on tilts with a east incline. Would these be set in a normal string or would they be wired up the same as you have shown in your diagram for east west also would I have to use optimizers? I would be using a Fronius inverter. I was informed by some solar installers that I couldn't have east, west and north on a 2 string inverter and they wanted me to install 2 systems so I sent them your post on how it could be done, I had a negative response and no quote on installing a system. Regards George

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Mark C said : administrator Report 4 years ago

Hi Edward. Thanks. I'm not sure if they cover your area, but try Penrith Solar.

Edward Fyvie said : Guest Report 4 years ago

Hi Mark, Great blogs, informative and unbiased! I am in the process of evaluating installer offerings for a 8kW system on an L shaped roof, 2 strings North, one East, one West. There is slight shading from trees on one North string. The first offer is for SolarEdge with optimisers, but after reading your blog, I'm inclined to go for Fronius + Tigo? Can you recommend good installers in South West Sydney? Thanks

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Mark C said : administrator Report 5 years ago

Hi Ravi, that sounds fine to me. If you are in Adelaide, I'd suggest giving the guys at Goliath Solar and Electrical a call. (Check out their reviews online too).

Ravi Subraman said : Guest Report 5 years ago

Hi Mark, Your article is very informative and educative for the common layman. Thank you. I am in Adelaide and looking to install a 6.615 Kw system with 21 x 315W REC Twin Peak panels and 5Kw Fronius inverter on my property with roof on the east and west. I have had conflicting suggestions from the few installers who have quote and hence seeking your expert opinion. Please advise if a configuration with 8 panels on the eastern side connected to MPPT 1 and 13 panels on the western side connected to MPPT 2 would work efficiently. Thanks in advance.

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Ben Neville said : administrator Report 5 years ago

Hi Gary, Two strings in series is fine, assuming one unparalleled string into each tracker. Problems only arise if you parallel 2 sets of panels into one tracker.

Gary Turner said : Guest Report 5 years ago

Hi Mark/Ben Just to clarify your answer to Cedric - assume you have a Fronius 5kw inverter which has an input current rating of 12A. Assume also two strings on panels in series each with 9.95A (ie LG NeON2). Can the inverter handle this? Does the 12A rating mean each string can be 12A or does it effectively mean each string can only be 6A? Which Fonius 5kv model would you recommend for two strings of 9.95A panels?

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Ben Neville said : administrator Report 5 years ago

Hi Cedric - two options here. We use the Sunpower 327W panels, which have a 5.98A input current, meaning we remain under the 12A input limitation of the Fronius Primo when paralleling. Or, when using panels with 9A input current, we utilise the Fronius Primo S.C. Inverter when paralleling. The S.C has the same specs and nominal output as the Primo I.V, except with 18A input current instead of 12A.

Cedric said : Guest Report 5 years ago

Hi Mark, great articles all round. How do you parallel up the Primo 5kW? Isn't it max 12 Amps and if panels are 9 Amp, 2 x 9 puts it over?

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Mark C said : administrator Report 5 years ago

Hi Julie, no we don't, but you have one of the better companies in Australia near you. NRG Solar in Richmond has a great reputation amongst their peers in the industry.

Julie said : Guest Report 5 years ago

Hello Mark, Do you have an installation service in Adelaide. Thanks

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Mark C said : administrator Report 5 years ago

Hi Julie. depending on where you are, I wouldn't focus on self-consumption, I'd focus on production. Read this blog. https://mcelectrical.com.au/blog/whats-best-direction-face-solar-panels/. The reasons installers don't do it is more because they don't understand it. When they understand it, it usually makes their life easier, as they have more roof space to work with. 180 degrees of separation isn't a problem, but couple that with 35 degrees and a short string of 6, and it isn't ideal, but it should be ok. The better option would be to install Tigo optimisers on the 12 panels, but that increases cost, and probably won't increase production by much. In short, maybe just keep it 6&6 paralleled east & west unless you can instal all 12 panels east or west.

Jules Baker said : Guest Report 5 years ago

Very interesting and clear article thank you very much . I'm installing a 6.6 kW system of 24 panels with 12 North 6 East and 6 West with the aim of producing power during maximum length of daylight hours to facilitate self consumption . I don't want to go to optimisers or micro inverters due to cost so must parallel two strings into one MPPT of a 2 MPPT 5 kW inverter My roofs are at nearly 35 degrees inclination so I am wondering whether an east-west split into the one MPPT would be inefficient as there is no direct sunlight on the opposing roof paralleled into the aame MPPT for a considerable period of the day . I therefore wonder whether the voltages will be equal ? Is this the reason why your article says that it is better for the parallel strings to relate to arrays only 90° separated ? If this is the case maybe I should split my north into two arrays of 6 and have North 1 and East paralleling into one MPPT and north2 and west into the other? Finally installers seem reluctant to parallel strings into the one MPPT. Is this because they are incurring some hidden extra cost apart from a few metres of extra cabling ? Like maybe additional isolators for each string... ?

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Mark C said : administrator Report 6 years ago

Hi Aiden, seems you have missed just one button. Above, the Channels the is "Devices". Click on the Devices and then select the Inverter. (If you have a smart meter or multiple inverters you can also check them).

Aidan said : Guest Report 6 years ago

Hi Mark, great blog. Just wondering if you can help me find the graph you show with the two separate mppt voltages against total power? This seems to be in the Fronius inverter homepage, however under my “chanells” tab I get no information. We have a Fronius 5.0-1 running 11 and 14 CSun 270’s split west and north respectively. It would be great to have some measure of how each string is performing individually.

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Neil Smith said : Guest Report 6 years ago

Hi Mark, thanks for your reply. Yes, I understand the IV curve business. But I'm still a bit wary of paralleling strings of panels (e.g. 2, or 3, strings of six nominally 24 volt panels, so the Voc should be about 6x30 = 180V). You talk about "fault conditions" possibly causing reverse current in one string - I presume you mean a worse "fault" than just an east-facing string having very poor sun while the west-facing one is brightly lit. What if, say, the connection to the MPPT input went open circuit? Would the east string then cop reverse current? Should it have a fuse to protect against this? If not, what sort of "fault conditions" do you have in mind? I'd like some reassurance, since paralleling unequally-insolated strings is exactly what I'd like to do!

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Cameron Quin said : Guest Report 6 years ago

Hi Mark, great article mate. Nice to see a lot of work put into an explanation piece for the whole industry.

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Mark C said : administrator Report 6 years ago

Hi Neil, In normal operation, current flows towards a load, which is the inverter connected to the grid. The voltage will equalise to the voltage that the MPPT of the inverter dictates. ... ... ... ... The "IV curve" is a whole other topic that I began to write about in this blog, but it seemed to complicate it unnecessarily. ..... ...... ..... However, in the case of fault conditions, you can get reverse module current where current from 1 string can flow backwards through the other string. Panels can handle a certain amount of reverse module current. Most panels can handle 15 amps. IF a panel can handle 15 amps, and we paralleled 3 strings of panels (at 9 amps each), then under fault conditions, the current of 2 strings could flow reverse through the other string and damage that string of panels (18 amps). So, in this situation, we would have to use a fuse smaller than 15 amps in the positive and negative of each string to protect the damage. This is called "string protection" It is usually only needed in commercial size jobs. Bit of a tangent sorry ;)

Neil Smith said : Guest Report 6 years ago

It would have been worth mentioning that when two strings are paralleled, the string which alone would have (slightly) higher voltage can't drive current in reverse direction through the other string. Like a good battery charging a bad battery. Is it because solar panels are fundamentally solid-state diodes? Or because they all actually have auxiliary diodes installed in series? Explanation of this point would be good.

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