What angle should solar panels be at?

Hey, it’s Stuart from IQ Solar. I am going to be doing a quick run-through, looking at a few systems in order to explain the best angles that you would use for installing solar. I’m going to give you a couple of examples. I’m looking at Nearmap here in my suburb of North Rocks, so I cannot tell a lot about this one except that it’s almost facing north. It’s probably installed at a tilt. It’s in April, so this is just about a month ago. And based on the angle of the sun and the length of the shadows, I’m guessing that these tilts are probably at about 15 degrees. So the document that I’m going to be referencing is the… Drag it on to the screen here. It is the Clean Energy Council Grid Connect System Design Guidelines, and there’s a page for every major city. So for example, I’m looking at Sydney right now, and there are as general as that, they don’t need to be suburb by suburb. It’s basically looking at the angle of the sun, so it’s going to be pretty similar for Sydney and a wide rear area around it. 

So the plane is the angle of the panels, so if I would… I guess before that, it was, say, 15 degrees. So it’s somewhere between these two columns, and let’s say that that system that we were looking at is just five or 10 degrees off north. So in trying to work out how optimal this is, it’s probably sitting in between here. So it’s a 15 degrees of the plane and 10 degrees of the azimuth. So it’s operating at somewhere between 94 and 98% of optimal. What optimally is, is a different story. I’ll talk about yield separately, and yield is typically what we’re talking about is how many kilowatt hours per kilowatt of system per year. But we could say that the system we’re looking at here is going to be operating at about 96% of optimal, and that’s assuming that these trees don’t shade it. It could be that in mid-winter, like when we get to… Let’s see if we just go back a bit. How long have they been here? Yeah, actually, yes, there we go. 

Middle of winter, they’re going to cop a tiny, tiny bit of shading, but it’s almost inconsequential when you consider this is going to happen for just a few weeks of the year. Anyway, so we said 96%. So if I zoom out and I go for a bit of a wander through the suburb, here is a house which has panels both east and west. So if I assume that this roof is at approximately 20 or 25 degrees, I just want to sort of determine what percentage of optimum these panels are performing at. So let’s say it’s between 20 and 30, some of those panels, so 90 would be east or west, and it wasn’t quite. So one of them is just above the east-west line, and one of them is just below in terms of orientation. So some of those panels are going to be operating at about 87%, and some of those panels are going to be operating at about 82. So this right here is going to be operating at about 87%, and this one right here is going to be operating at about 82. I hope that makes sense in terms of this graph. I’ll find another example as well. 

There’s more to this, and the extension of this is not just about output, it’s about when people use power and matching up consumption. So, for example, if I was advising someone in this house to look at solar, I would actually put it more on the west. And the reason is that the usage… Most people’s usage is less in the mornings, especially if they get up and go to work, than it is in the afternoons when they come home. And if there’s kids in the house, they turn on the air conditioning or the heating, and they are using various things. Westerly facing systems, in my view, are better than easterly facing systems even if the output is the same because it matches up with consumption patterns better. Let’s zoom out and find another one as an example. Here we go. So much solar. So this house has a system which is mostly facing northwest. It’s probably just a little bit… In old speak, it’s probably north-northwest, and let’s say this house is also on a 25-degree pitch. 

We’ll just have a look at this graph. So for example, it’s in between these two columns, it’s almost… It’s facing slightly more north than it is facing west, and if it’s at 25 degrees, then we’re talking about 97% performance. So basically, things that are northeast or northwest are really almost as good as north. Things that are east or west are probably about 14-18% of optimal, and northeast or northwest is only a few degrees, a few percentage of optimal. Hope that makes sense. 

Let’s have a quick look while I’m here and see if I can find anything that’s on tilts on a home. People used to put systems on tilts. This could be one. This is interesting. They’ve gone for a system where the roof was pitched southwest, but they’ve put them on tilts so that they faced northeast. This is a very interesting example. I’m just going to scroll back and see when this was done, so in Nearmap, I’ve got a timeline. So they weren’t on in 2012, they got put on at some point in 2012 or ’13. Anyway, what’s interesting about that is that practices change. Solar panels used to cost a lot more than they do now. So people used to do all sorts of things to optimize the output of panels. If this system is going on now, the additional cost of the tilt frames, which is somewhere between 40 to $50 per tilt frame, including the hardware and installation, is simply not worth it. The best practice now would be to put them all facing southwest, but put on a bigger system. So basically, take the loss associated with a lower performance, but put on more panels because panels are cheaper now than they used to be. 

So if you go back 10 years or 12 years, you saw a lot of homes with tilt frames, even on a roof that was facing west or east, and they would tilt them up so that they faced exactly north, which you just simply would not do now, you would just put on a larger system. Anyway, the purpose of this, and I’m going to link to this document, is to understand this table. It’s not that insured of… You have to rethink about it, but let’s say you’re on a very low inclination commercial roof and it was only 10 degrees, the direction really doesn’t matter a great deal. If it’s north, you’re going to lose 6%. If it is actually facing south at 10 degrees, you’re only going to be losing 19%. So you can then work out the cost associated with tilting versus not tilting and for a home, it’s just typically not worth tilting partly because it’s ugly, partly because it reduces the size of the system that you can fit on. So looking at this one here, they have to allow so much spacing between rows because these will self-shade back. If they were flat on roof, you could put on twice as many panels without any issues at all. All right, sorry for the long explanation, but I did want to dive into this table a little bit and share this, in case you are geeky enough to want to look at your system performance.

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