Solar Power Generation Comparison | East/West vs. South Facing Roof 

Glad it was helpful!

Yes lucky is right!

Thanks for the feedback and I'm glad to help!

Wow 20kW is huge!

I'm glad to hear it was of help. I wish you the best in your pursuit of solar!

This is what I’m wanting to do with my 2kw solar array I have them all facing south and am wanting to do an east west orientation trying to figure out how to do it with one combiner box feeding my MPP LV2424

@@ElectricTechAdventures in the SLC area's and if i have to pick purely one side of the roof for now aka pure east or west on a 10 to 20kw finale sized system/my islanding equipment maybe start with about 500w to 2kw panels to formularise my self with the installation/running ect. and the same questions for SE vs SW pointing the panels? residential vs commercial 72 cell as the roof line is a 20* ish pich common to are areas A-frame/ranch aka flat tar-paper

Helo i am from pakistan i have installed a structure my direction is 160 degree south does moving it to 180degree south will make any difference if yes then how much?

@haris only 3-3.5% maximum. Not more than that

Yes I agree, I think the production difference certainly justifies prioritizing south facing roof space first, then secondarily install on east/west as makes sense based on potential shading, orientation of house to street (most people prefer panels on the back of the house for aesthetic reasons) etc... I've appreciated your solar videos in the past, so thanks for helping to inform people about solar!

That's a great question that I don't know the answer to or even how to figure that out. I've heard of computer software that simulates various solar installations and their output over specified periods of time that would maybe be able to figure out the difference. I certainly don't know.

Good point. Here in Utah when we have storms (not often) they usually kick up in the afternoon.

Thanks for the positive feedback!

Those all sound like great improvements! After my roof was full of panels I then covered my RV and added batteries and inverters so now I also have solar for camping and when the power grid goes down. I've made videos about that too if you're interested.

@@ElectricTechAdventures Thanks Anthony, great help. I'll watch them, I just found your channel. I have two systems, the SE that was a grant from NYPA (New York Power Authority. I'm in the western Catskills, 42 latitude) and one I paid for using two Outback VFXR3648 inverters that do intertie / off grid with 15kWh of LiFePo4 batteries. That system is 4.2 kW but I'm trying to get a permit for my stream to do microhydro.

I wish more homes were built with solar in mind for the future. What state do you build in?

Hopefully there's a monitoring dashboard the installer can give you access to. I suggest looking at the panels individually to ensure they're all producing. Otherwise this is an issue you'll need to take up with your installer. There's too many unknowns for me to be helpful.

I think you're on the right track with doing a combination of south facing and west facing solar panels. I agree it's very fuzzy determining anything exact with solar production. There's a lot of variables, and they're all changing from day to day, throughout the annual solar cycle plus the weather is constantly changing. In general I've found it's beneficial to just have more solar panels then you have the power when you need it in less ideal circumstances, but you'll waste potential solar energy on sunny days when your batteries are full. Depending on your willingness to adjust your lifestyle you could also adjust your electrical consumption depending on the availability of the solar. I don't yet think that batteries are cheap enough to go completely off grid just to save on the differences of peak times, but that does depend on the details of your specifics. Here in Utah it doesn't make financial sense to install a battery just because of solar net metering fees, but it is great peace of mind having batteries and you can't put a specific price on that.

In an off-grid or a system with a battery where you want to maximize direct consumption of the solar energy I would suggest that an east west orientation is best. As you've outlined if you use more power in the evening then the west facing panels will be the most beneficial at that time of day. Obviously the best is for panels that follow the sun throughout the day, but from what I've seen that mechanism is expensive compared to just putting out more solar panels in multiple orientations. Typically in an off-grid situation there's space for a ground mount solar array and in that case I'd consider putting east, south and west panels if I had the space for that, and I'd mount the panels on a rack system that can be raised or lowered to match the angle of the sun which varies throughout the year. I'd adjust the panels periodically like weekly or monthly or however often I'm willing to do it.

@@ElectricTechAdventures I have 3 roof's areas (east, west, South all with plenty of sq. ft.) Initially I was inclined to do just south but felt that a mix of power throughout the day. It's a challenge, cause I don't have a full map out of my loads but guestimate is after 3pm is 80% and evening big on AC. It's all about when and how you use your power.

Thanks for sharing your findings, and thanks for watching!

Glad it was helpful!

@@ElectricTechAdventures may I know what software did you use for simulation.

@@marwafaris8288 This wasn't a simulation, it was real world performance of my house and my neighbors house using the SolarEdge inverter monitoring portal.

@@ElectricTechAdventures I know that, I mean before you install the PV system are there is any simulation you use it and thank you for your answering

@@marwafaris8288 No I didn't attempt to simulate anything. I just oversized the array 30% initially to make sure I had enough. In reality solar is quite variable so simulations are still only going to be a rough estimate. As an example of variability, in October the last 2 years my solar produced 1.51 in 2019 and 1.44 MWh in 2020. And yet in 2021 it only produced 1.06 MWh with no system problems. Just the weather was very stormy and overcast this year in October.

Great 👍

Do you need 2 combiner boxes to do an east west ?

If you're trying to simply maximize production then south facing is best, but just barely. If you're trying to consume more of the electricity directly then East West is actually better. The differences in orientation are less important than the angle of the panels, or shading issues.

Pricing agreements with utility providers vary dramatically around the world. In my case as well as my neighbors we pay a flat $10 per month and the grid serves as our battery. Every kWh we push into the grid we can later pull out of the grid at no cost to us until our March bill of every year where if we have a credit on our net metering account then we lose it. They do not compensate us for any excess electricity at the end of every year.

@@ElectricTechAdventures We had flat rate agreements like that maybe a decade ago. They are unsustainable, and will definitely disappear as your renewable grid mix rises. Our overall grid mix is currently 82% renewable, and I'm enjoying almost free charging for my EV, but I doubt it'll make financial sense for me to get solar panels.

@@virtual-viking Our net metering agreement is grandfathered in until 2035. My expectation is that by then batteries will be cheap enough that it'll make sense to add those to our system to self consume as much as possible so as to transact with the grid as little as possible. But then again that decision will be effected by what the net metering policy is in 2035. We'll consider the factors at that point in time. Our solar panels have already produced enough value in energy produced that they've paid for their installation costs as of mid-2023. Now going forward we're driving for free on the sun, and we're also partially heating our home with the excess solar electricity in the winter which last winter halved our natural gas bill.

Glad it was helpful

Thanks for the feedback!

It might be even closer, than 15-20%, remember in winter, there is high chance of snow, fog, and bad weather, and in general the production because of the shorter day is lower. So that means in winter, even if the production of east/west array is, let's say 30% lower than south array, by looking at kilowatts it's still not a big difference. And beside that in summer, southern roofs are hotter, which decreases efficiency of the panels. And beside azimuth orientation, the efficiency of solar production is affected with the angle of the roof aswell. So I wonder if his neighbor has the same angle of his roof than he does... By assuming all these factors real factors, I think that perfect east west array (azimuth of 90° and 270°) might be very very comparable with southern array of 180°.

@@anzman911 Hi, it's just my experience when comparing with colleagues who have a nigh on identical array but with a south orientation. The azimuth angle is extremely significant in the northern hemisphere when comparing E/W and S output. In my experience, it is the cause of the difference in generation between the 2 during the winter months. It is over 50%. By mid-March, both E/W and S are pretty comparable.

@@andreashessler838 Thank you for sharing your experience. I've just installed 16kw sollar array, 9 panels facing exact south, 14 facing exact east and 12 facing exact west (that's what's possible on my roof). I wonder how they will perform in winter. But I confirm, since mid march my power peaks are growing daily let's say last week of february my peak was 8.7kw, mid march 9.8kw, now it's 12kw. Interesting.

@@anzman911 Wow! You will be able to power the town 🙂. I've got a 4.5kwh array with 5.2kwh battery storage. Aside from mid-November till February, I generate and store enough to cover our usage (with help charging the battery at a lower price tariff during the night when the weather is off). In the summer, we generate more than we know what to do with and a load of it goes back to the grid. This is a shame as I only get £0.04 per kWh for it. I try my damnedest not to send any back if I can help it. I'm looking at adding another 2.6kwh cell as the battery storage is just a bit light.

Thanks for the feedback and I am glad that it helped you! One thing I have found with solar is that it is quite variable not only between different installations but even year to year with the same installation. So don't get too caught up with expectations but enjoy the solar power you get within the constraints of what available roof space you have etc.

@@ElectricTechAdventures yes sir thank ya

I did talk about that in my 50,000 kWh generation update two years ago at 11 minutes into the video. Here's the link. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-3BrbyBLm_Mw.htmlsi=vTVi-_c569h7x-lv&t=661 Is there something more specific I didn't address in that video that you'd like me to elaborate on?

Yes I agree with all your observations. The most ideal for even power distribution is an expensive solar tracker. The ideal cheaper option is panels facing a combination of all the directions, but if the array is rooftop mounted then you're limited by rooftop surface angles.

I agree that you might as well generate electricity using them and then hopefully you can pick up a electric vehicle and utilize that energy. I find great peace of mind being able to drive around in our electric car using our solar energy and not being affected by the gas prices at least directly at the pump. Obviously the high prices are affecting food and other things that do affect us and we can't really do much about that.

I wish all HOAs would chill out about solar panels and just let people install them if they want. I wish you the best in your solar pursuit, it's been very worth the effort to me!

East and west facing panels have very similar outputs, if same shading and roof slope. That’s why the software showed same production when six panels were moved. In support of this, the difference in output of our east and west facing arrays is less than 1% The south array produces 25% more than each of the other two

South is better so that being part of the combination is probably better and then West is also better because you get more energy production in the hot afternoon when you need it the most for air conditioning.

@@ElectricTechAdventures thanks I found nice comparison about South facing system and south west facing system and 100% south in real is just 3% better than south west over the year so I'm not in bad position at all. I expected more difference

RU-vid has the location displayed right at the top of the description box, right after the date it was posted and number of views the video has. Salt Lake City Utah area.

The southeast direction of your house will produce power just fine and I would definitely load up that direction with as many panels as possible. Then if you still want a larger array and you have no space on the ground the northwest direction will generate some power but it will be less effective especially in the winter season when the sun is low in the sky to the south assuming you are in the northern hemisphere. East West and South are similar in production as I demonstrated in this video but North facing is not great. If you are able to mount the panels on a bracket that makes the panels at least horizontal instead of at the angle of your roof facing north then that will improve production. There's a house in my neighborhood that did just that.

@@ElectricTechAdventures thank you for a detailed answer.

You need to switch your solar array sizes, my neighbor's solar is 6.67 kW and mine was 6.38 kW in 2018 and you said "You may have more solar panels, but the system can only put out a maximum of 7.6-kWh, and their system can only put out a maximum of 5-kWh" so switch the system sizes, and also you said kWh where I think you meant to say kW. I somewhat follow your calculations, but I'm not clear in the point you're making. The end result in the year with very similarly sized arrays was that south facing (mine) produced a little better which is what most people would expect. Yes my inverter was larger than it needed to be, but that's not a large detriment to my power production from an efficiency prospective. There wasn't a single day in 2018 where the inverter reached it's maximum output. Now that my array is 9.98 kW the inverter still only reaches it's maximum for a couple months each year, peaking in May and for some reason it maxes out at 7.8 kW, not 7.6 kW.

Anthony Dunster I had some mistakes, but the original way of dividing by the size of the inverter is correct. You obtain a measure of hours rather than energy or power. It, also, provides a measure of efficiency. Which inverter can produce at full power the most hours given a certain inverter size? The inverter of your neighbors did in 2018. The limiting factor is not the size of the array. It is the size of the inverter. I did not see the annual energy produced after you increased the size of your solar array in order to repeat the calculations again. However, increasing the size of the solar array should have done two things for you: 1- it should have made the inverter the only limiting factor in energy production. 2- it would have increased the size of the ratio of solar panels to inverter size. The efficiency of an inverter is an inverted parabola. If you have few solar panels as you did in 2018, as you increase the size of the solar array, it approaches the maximum point in the curve. In absolute terms your system did produce more energy in 2018, but your inverter size is much bigger (52%) than your neighbors. On a relative basis, they did much better given their smaller inverter and their handicap of not having their solar array facing South: (10,830 / 8,440) = 1.28. In other words, their system produced only 28% less than your South facing system with an inverter that is 52% bigger than theirs. Hopefully, this will make sense now.

@@ek9772 I still don't understand the fixation on the inverter. The comparison of the inverters' output in 2018 ignoring the solar array input is what doesn't make sense. My larger inverter was less efficient yes, but very minimal difference. I've now had my 9.98 kW system for 14 months and comparing the first 12 months of the 6.38 kW system vs the first 12 months of the 9.98 kW system showed only a difference of a couple tens of kWh over a year which could easily just be differences in weather. Regardless of inverter efficiencies, my 2018 south facing system produced more kWh than the slightly larger East/West array and ultimately that's all that matters. Unless you're trying to even out the power production over the course of a day to accommodate specific hardware limitations or something.

Anthony Dunster I was stating a fact. Their solar system was more efficient than yours during 2018. The question is why? You seem to boil this down to making more watts, but it is not that simple. As I stated before, their system produced 28% less energy than your South facing system, and they did this with an inverter that is 52% smaller than yours, and as you mentioned several times the size of both solar arrays was almost identical (a difference of 6.67 / 6.38 = ~ 1.05). Let’s look at the numbers in detail: Solar array difference: Their solar array was 5% larger in 2018: (6.67 / 6.38) = 1.05; 1.05 - 1 = 0.05. Inverter difference: Their inverter was 52% smaller in 2018: (7.6 / 5) = 1.52; 1.52 - 1 = 0.52. Energy produced difference: Their energy production was 28% less in 2018: (10,830 / 8,440) = 1.28; 1.28 - 1 = 0.28. A quick table of facts: Solar array difference: 5% - their solar array was larger. Inverter difference: 52% - their inverter was smaller. Energy produced difference: 28% - their energy production was smaller. Orientation of panels: Your solar array facing South, and their solar array facing East & West. All the data seems to be against them with the exception of a solar array that was 5% larger than yours in 2018. Their array seems to be pointed in the wrong direction; their inverter is significantly smaller than yours, and, yet they managed an energy production gap difference of 28% against your generation of energy. I don’t know about you, but I would have expected a bigger difference than 28% in energy produced. This is particularly true given the inverter difference. The only way that I can explain this is by looking at the ratios of solar array size vs inverter size. Their ratio of their solar array size to their inverter size in 2018 was (6.67 / 5) = 1.334. Your ratio of solar array size to your inverter size in 2018 was (6.38 / 7.6) = 0.8395. Every study that I know suggests that these ratios are a major part of the explanation for the above results: www.solarpowerworldonline.com/2016/07/solar-inverters-clipping-dcac-inverter-load-ratio-ideal/ new.abb.com/docs/librariesprovider117/default-document-library/solar-inverters/solar_power_world-article.pdf?sfvrsn=80a7614_4 These studies seem to suggest to have a ratio larger than unity of more solar panels to inverter size, but they suggest not to over do it. And this is exactly what happened with your neighbors’s system in 2018. Your system on the other hand was not even achieving parity in this ratio exercise in 2018. In 2019, you increased your solar array size, and kept the same inverter. This turned the odds in your favor. Now you had a larger inverter, a larger solar array, the orientation was kept facing South, and the ratio of solar panels to inverter size (9.98 / 7.6) = 1.313 was above unity. Notice the efficiency curves in the next file. The curves shoot up, and then they remain fairly constant at a high efficiency level once they achieve at least a third to half of their nameplate capacity. In other words, these SE inverters can achieve this efficiency levels when the ratio of the solar array size to the inverter size overcomes 30% to 50% of inverter size. www.solaredge.com/sites/default/files/application_note_solaredge_inverters_efficiency.pdf As I mentioned before, I could not calculate the original numbers in my first message since the information was not shared for 2019. Namely, in 2018 (10,830 / 365) / 7.6 = 3.9 the efficiency of your system was 3.9. I bet your efficiency for the first full year of production data with the larger array will be better than this number, and I would be curious to find out if in spite of having a smaller ratio of your system, 1.313, to theirs, 1.334, it produces a higher efficiency number than their number, 4.6, in 2018. These efficiency numbers are key for me in determining if a solar system is performing well. It is not that I obsess over inverters. They are simply one of the pieces of a larger puzzle.

@@ek9772 Wow, I appreciate your depth and efforts in explaining your calculations in great detail. I still disagree with the calculation you've proposed including the inverter size in the calculation and I hope you'll agree to disagree. I've looked at my actual output numbers, but keep in mind there's always going to be variations from year to year. I'm aware of inverter efficiencies so I fully expected the system to be more efficient once expanded. From the morning of July 28th 2018 through July 27th after dark 2019 my 6.38 kW array produced 10,446.07 kWh. For the same period (morning of July 28th 2019 through July 27th after dark 2020) my 9.98 kW array produced 16,492.19 kWh. Dividing those total outputs by the Watts of the panels shows that the 6380 Watt system generated 1.637 kWh of electricity per Watt of panels that year. The 9980 Watt system produced 1.652 kWh of electricity per Watt of panels. That's a difference of 0.0152 kWh generated in an entire year which is very minimal and is within what I'd expect as variance just from weather alone. My conclusion from this calculation is that inverter efficiency from load (or lack of load) is not very important based on my real world data.

What do you mean? Can you elaborate?

@@ElectricTechAdventures Sure. With more and more people into solar there is an excess around noon due to south facing panels. Dutch energy companies and government want stimulus for panels east and west and will do this with lowering the pay back in peak hours. Same happened alreaydy with months . You now get paid excess per month only and cannot defer it to a next month although here the government disagrees still. Summarizing: It is maturing to question and demand. Your own small energy station enters a market. Be aware that we have farmers in Netherlands with hundreds of panels on roofs.

@@goudhaantje3569 oh you're referring to net metering agreements. I don't attempt to address that because it varies too wildly across the US and world. Pairing batteries with solar allows for self reliance and protection from the terrible net metering policies out there.

How does this video say SolarEdge isn't reliable? Both of ours inverters have worked fine for 5 years now.

@@ElectricTechAdventures Well it was more.... out of your sample size of two systems 50% of solaredge systems had had issues with losing 2/3rds of it's panels??

@@MrButuz I know nothing about the problem that occurred in that situation. It could very well have not had anything to do with the inverter and everything to do with the wiring. It was installed supposedly by a professional installation company whereas mine was installed by myself. I don't think there's any takeaway here about SolarEdge specifically.

@@ElectricTechAdventures Hehe ok I was just joshing - you did a great job with your DIY that's for sure looks better than a lot of pro companies.