Are you wondering if your roof is suitable for solar panels?
It might not sound like a big question, but it’s important. It’s something you really should be asking yourself early in the solar panel shopping process if you haven’t already.
How solar panels fit on a roof is intricate. You need to consider the direction the panels will face, the pitch of the panels, and their relationship to the sun. When you begin to factor in energy consumption patterns, you realise there are as many unique configurations for solar panels as there are points scored in Nathan Cleary’s career for the Penrith Panthers (it’s 1,421). He is a kicker though, so that throws off the stats a bit.
At Penrith Solar Centre, we get a lot of questions about how the roof shape and your home’s relationship to the sun affect the orientation, pitch, and azimuth (that’s a fun vocab word we’ll get to later). We’ve worked with countless customers over the years and each of them has had unique solar needs.
In this article, you will learn about the following:
- Which Direction Should Solar Panels Face in Australia?
- How Productive Are Solar Panels in Relation to Each Compass Direction in Sydney?
- Personal Consumption Pattern Considerations and How They Affect Solar Panel Placement
So get comfortable as we dive into everything you need to know about your roof and how to place solar panels on it.
Which Direction Should Solar Panels Face in Australia?
We live in Australia. The vast and mysterious Southern Hemisphere. The sun makes its way across the sky to the north of us here in the Sydney metro area. So your solar panels should face north, right? That should maximise productivity, right?
That’s absolutely a trick question. While the compass direction your solar panels will face does play a part in productivity, there are many other factors to consider.
In the solar industry, anytime anyone asks about the efficiency of something, the correct response will forever be this: it depends.
Every household’s energy consumption patterns and energy needs are unique. It’s far more important to consider when you’re using your energy than how much light the northern face of your roof will receive in the summer. This will help maximise your solar panel productivity.
But before we get into energy consumption patterns and the role they play in solar panel placement, let’s look at what’s happening outside the house first. Much like The Drifters 1962 classic, we’re going Up On the Roof.
There are a few key terms that we’ll use as we discuss solar panel placement on the roof. They are:
Pitch: The pitch of the solar panels is the angle of their placement in relation to a horizontal surface, the ground for instance. The slant of the roof is factored into the pitch of the solar panels. On a slanted roof, you might see panels with one side of them lifted to get a more productive pitch, but it’s not especially common.
Angle: You’ve taken geometry, so you know this term, but it’s been a few years. The angle of the sun and how it relates to your solar panels is what we’re concerned with here. When we install solar panels, the angle of the sun’s rays and how they interact with the pitch of the roof is important. The angle of the sun in relation to the home is necessary when determining the pitch and placement of the panels.
Azimuth: This is a great word. The best way to define it is by giving an example. Imagine you are standing in the middle of a giant compass that’s lying flat on the ground. It goes from 0° to 360° because it’s a circle, right? The azimuth is the compass direction – with you in the middle in relation to a heavenly body. In this case: the sun. North is 0° and south is 180°. If it’s noon and the sun is high in the sky to the north, then the azimuth is 0°. However, if it’s 3:30 pm then the sun is in the west making its way towards the horizon, then the azimuth is closer to 340°. You’re still in the middle of the compass, but the sun has moved. Here’s a handy picture to illustrate it…
Now then, we’re going to use our new fancy vocab words to go through an example of solar panel placement and efficiency. Everything we’re about to talk about is for the Sydney metro region only. Because Townsville is closer to the equator than Sydney, the angle of the sun and the pitch of the solar panels in relation to the azimuth of the home would be different than it would be at our southern latitude.
The sun is north of Sydney most of the year as it makes its journey from the eastern horizon to the western horizon every day. So then, for the purpose of this example, the solar panels are installed on the northern face of the roof.
The pitch of most of the roofs we service is usually around 20° and the solar panels are installed flush with that roof face. So the pitch of the panels is 20°.
The azimuth of the home (in the direct centre of a giant imaginary compass on the ground) will be true north at 0°.
When the sun is at true north, 0°, and the pitch of the panels in relation to the ground is 20°, then we are able to calculate the productivity of the solar panels at 98% at that time of day. Obviously, if it’s cloudy or part of the panel is obscured by shade, the productivity drops to a lower percentage.
At 4 pm, however, the azimuth is at 300° because the sun is further west in the sky. The productivity of those north-facing panels drops to 86%. The angle of the sun’s rays is shining less directly on the solar panels than it is at high noon.
One thing to remember as we move forward giving examples and using math: the angle of sunlight hitting the solar panels will always vary because the sun’s position in the sky changes every season. In our numbers, we’re using averages that account for the entire year. For the purposes of the math in this article, we’re unable to explain pitch, angles, and azimuth for individual seasons. All figures are based on year-round averages.
How Productive Are Solar Panels in Relation to Each Compass Direction in Sydney?
As mentioned above, where a home is in relation to the equator is an important factor when determining how to place solar panels on your roof. But the sun doesn’t follow the same pathway in the sky for homes further away from the equator. It shifts seasonally from north to south. In the summertime when Sydney is closer to the sun because of the tilt of the earth’s axis (it’s 23.4°, FYI), the sun is higher in the sky. In the wintertime, as you’ve probably noticed, the sun is closer to the northern horizon as it travels from east to west.
How does this affect solar panel placement and efficiency?
Year-round, a northern-facing roof will get the best sunlight consistently throughout the day. The sun ranges from close to the northern horizon in winter to right above us in the summertime. That range of the sun’s angle in relation to your solar panels guarantees maximum absorption of the sun’s rays year-round.
But the sun isn’t just to the north and above us during the day. It’s also near the east in the morning and in the west in the afternoon. What about putting panels on the east or western roof faces to absorb the sun’s rays more productively in the morning and afternoon? It’s a great consideration, especially if your energy consumption patterns are aligned with the sun in the morning or evening, and we’ll talk about that soon. That’s a good question though, and I like the way you’re thinking here.
Let’s talk about the elephant in the room of solar panel placement in Australia: southern roof faces. One of the biggest myths and misconceptions about southern roof faces in Sydney is that they aren’t a productive place to install solar panels. This couldn’t be further from the truth. The sun shines on southern roof faces just as much as it shines on northern-facing ones (albeit from a different angle which determines the intensity/productivity of the panels based on the season). Unless of course there’s some shading getting in the way.
Here’s a bit of math to help you understand the productivity of those southern-facing solar panels and why you might consider installing them there (especially if your northern roof face is obscured by the shade of a big, beautiful tree you can’t bear to chop down. And why would you? Trees are beautiful. Before we get to the math, we recommend you check out this lovely poem by Joyce Kilmer about trees).
If your southern roof is perfectly facing south, then it would have an azimuth of 180°. The exact opposite of north, which is 0° in the example we used above. That makes sense, right? The opposite side of a circle (compass) is 180°.
The sun is shining down on your home at noon and the angle of the sun’s rays are hitting your southern-facing solar panels. Because your home is like most homes, the panels have a pitch of 20°. This means that the solar panels on the south roof face will operate at 73% productivity. That’s not too shabby.
A steeper pitch on that roof face would challenge your solar panels though. If the pitch of the solar panels were 30° and we used the same numbers (high noon azimuth of 180°), then the productivity drops to 63%. That’s when you should question whether to install solar on that roof face. That’s not great efficiency.
It should also be noted that if it’s summertime, the sun will be higher in the sky above the home and will provide more direct sunlight on the southern-facing solar panels because of its angle. And in the wintertime, that same southern face will receive a much less direct angle and result in less productivity. But we’re working with year-round averages. A solar consultant will be better able to address that with you in a one-on-one session. Anyway!
Here’s a hypothetical situation: the following is an image of a home that has a northern and a southern roof face. In this photo, north is at the top of the photo and south is at the bottom. As you can see, the home is at a slight angle in relation to compass directions, but that shouldn’t make much difference to the azimuth between the home and the sun.
On this home, a lot of the panels are located on the southern face of the roof. There are two banks of the instalment facing north, but it’s that big bank on the southern roof that’s interesting. The pitch is 20% on both sides.
The northern-facing solar panels operate at around 98% productivity. The southern bank is 73% productive, which is preferable to installing a bank of six on that empty patch on the north face that’s still empty (right of the two skylights). That bank of panels on the southern facing roof is more efficient than a smaller bank of panels facing north. It’s a numbers game.
In the summertime, when the sun is immediately above the residence, both north and south faces would get equal amounts of sunlight. Winter is a different story, with the north face getting the lionshare of the sunlight and the southern face getting far less. Remember that the percentage of solar panel productivity is calculated as a year-round average.
One last thing to mention about solar panel productivity: flat roofs. If you have a flat roof, like we do here at Penrith Solar Centre, your solar panels may have a 0° pitch. Your efficiency will be right around 87% all day. The azimuth is not a factor at all because the angle at which the sun’s rays hit the solar panels never changes. They are all facing directly skyward. Incidentally, we would never install panels at 0° pitch. The pitch needs to be at least 3° for the panel warranty.
Personal Consumption Pattern Considerations and How They Affect Solar Panel Placement
How and when does your household use electricity?
This is key when determining solar panel placement with your solar installer. If they aren’t immediately asking you about your energy consumption patterns, then you need to find someone else to install your solar panels. It’s that important.
Now you’ve probably already considered your energy consumption patterns, otherwise, you most likely wouldn’t be installing a solar system. But in case you haven’t, here are a few questions you need to ask yourself about how and when you use electricity:
- When are you home? Is the sun up? Are you retired or working from home? Or are you using electricity primarily in the morning and evening?
- What types of appliances are you running? What time of day are you running them? If you’re home during the day and it’s hot outside, what do you set the air conditioner to? What type of lights do you use at night?
- What time of year is it? Running an air con or a heater is seasonal, and each has different energy requirements. In the summer, you don’t need to turn lights on as early as you do in the winter, and in the winter, you probably aren’t using the pool.
There’s a lot to consider when you start looking at how you use electricity.
How does this information factor into the placement of your solar panels? Great question – let’s get into it with some hypotheticals (we love hypotheticals).
In these hypotheticals, you’re going to see examples in terms of east/west solar panel placement. We’ve elected, for the purposes of these examples, to stick to the same roof design for each example to best show you how energy consumption will affect the same roof in different ways. And we chose an east/west design because you probably understand the importance of northern-facing panels and the possibilities of southern-facing panels by now.
The compass points in each example correspond to each side of the image. North at the top, east at the right, south at the bottom, and west on the left. Don’t forget that each of these hypotheticals is based on year-round averages and doesn’t account for seasonal differences in angle, pitch, and azimuth.
Hypothetically speaking, you’re a family of four. Your kids are in primary school (cherish these moments, they grow up so fast) and you and your partner work. The kids are involved in extracurricular activities which you pick them up from on your way home from work, and your partner gets home about thirty minutes after you. All told, everyone is home by 5 or 6 pm.
The kids do their homework and you and your partner cook dinner. The air con is cooling the home off because you have western-facing windows that get direct sunlight. Some lights are in use, but they all get turned on in addition to the TV by 7 pm when the sun sets. You use electricity primarily in these evening hours into the night. You’re keenly interested in a solar battery or two to maximise your solar system because of this.
As you can see, two thirds of the solar panels are on the western roof face. The hypothetical family uses most of their electricity in the evenings, but they are there for a couple of hours in the morning before everyone leaves for work and school. That eastern bank of panels is there to account for that.
With a battery or two, those panels are going to soak up sunlight during the day when the family is away, charging for use at night. In the morning, the panels will be absorbing more irradiation because the pitch is more favourable in relation to the sun. Same with the western panels in the afternoon. However, at midday, those two banks of panels will be operating at the same efficiency with the sun directly above the home.
Hypothetically speaking, you’re an artist who has made a successful go of it professionally. Your paintings are sold routinely (or routinely enough) so you don’t have to work a side hustle. Well done you! You’re home all the time throughout the day (except for the occasional errand) working on producing more paintings. Most of your daytime hours are spent in a bedroom you’ve converted into a studio for your painting. You chose this room because the windows face east, you do your best work in the morning, and you love the morning light and the way it interacts with the colours on your palette.
The sunlight coming through the windows keeps the studio warm. In the afternoon, you need to turn on some lights in the studio because your eyes are seasoned. While you use electricity all the live long day because you’re home and you’re working, you use considerably less in the morning hours than you do in the afternoon when that gorgeous light shines on the rest of the home. Because you’re home all day, there’s not much point in investing in a solar battery.
I know what you’re thinking: why are there more or less the same amount of panels on either side of the roof? It looks like it’s an even split between east and west. We did go into great detail about how much time is spent working on the eastern side of the home where the sunlight shines through windows. About that… You’ll probably need an air conditioner or heater depending on the season. If you have a morning routine that uses electronics, and most of us do because we cook breakfast and watch TV for the morning news. Without a battery collecting energy from your panels, and without a northern roof face, you have to configure the panels to maximise that sunshine. In this case, east and west – morning, midday, and evening.
Hypothetically speaking, you’re a worker for a railroad company. And you work all the live-long day. Just kidding. You’re a shift worker who is only home between midnight and noon regardless of the season. Wow, you work hard and should consider finding a better work/life balance or you’ll burn out. Anyway, because you’re environmentally conscientious, you’re going to purchase an electric vehicle soon, probably a Tesla.
When you get home at midnight, you just open some windows and get that cross-breeze working for you, so you don’t have to run an air conditioner until the mid-morning in the summertime. You do get cold in the winter, so you do use a heater for part of the year. Reading is your hobby, so you’re not spending electricity running a TV. That being said, you do enjoy reading in your massage chair which uses a lot of power. Lately, you’ve been studying solar, specifically solar batteries. You have to charge that Tesla after all. And you’re not home during the afternoon, so the electricity from the solar panels you want to install would be wasted otherwise.
In this case, the majority of the solar panels are on the eastern roof face. A shift worker who leaves the home around noon will need solar power in the morning when they’re home. The western bank is to help collect sunshine in the afternoon for that solar battery (remember the Tesla?). And in the examples mentioned above, both banks are going to collect the same amount of sunlight at midday and the eastern bank is still going to be fairly productive through most of the afternoon.
Remember that the hypothetical examples above are very general to illustrate considerations for solar panel placement. There are more nuanced things to take into account that will vary from roof to roof and household to household.
How Will You Maximise Your Solar Panels?
So where should you place your solar panels?
On the roof, silly.
Sorry, couldn’t help but make a little solar installer joke. You have no idea how many times a day we get to throw that one out there with customers.
As you’re shopping for solar systems, it’s crucial to understand how the sun will interact with your panels. And where those panels are placed on your roof is huge. The mathematics of how the sun orbits over your home is important, but equally important is an honest evaluation of how and when your household uses electricity.
The best thing you can do when shopping for solar systems is to have thorough information about your energy needs ready once the installer starts looking at your property. If they aren’t asking you about your energy consumption patterns, you might want to shop elsewhere.
At Penrith Solar Centre, we will always ask you about your energy consumption patterns. It’s what we do.
If you’re interested in learning more about solar system efficiency, you might want to check out this article about the most efficient solar systems out there titled What Are the Benefits of a Microinverter System?