In Australia, solar panels will generate the most energy over the course of a year when they are facing north. This is especially important in winter when the sun is lower in the northern sky.
Technically, the panels should be tilted north to match the angle of the sun, however tilting panels basically just pushes output from summer to winter, so if you have a flat roof and you use more power during summer it actually makes more sense to leave the panels close to flat with just a little tilt to ensure that rain flows off the panels and doesn’t pool on the surface. If you have a pitched roof, then we will always install the panels in line with the roof.
If your house has a north-south roofline with the option of installing the panels east or west, we can install panels on either roof section depending on what time of the day you use the most power. Many families will use more power in the afternoon when the kids are home from school and the air conditioner and pool pump are running. If this is the case we would recommend installing your solar panels on the western roof, or we could do a split system with most of the panels west and a few east.
We can split your array by using Enphase microinverters. This can also help avoid shade later in the afternoon as pictured below. You can see in this image we are using 3 sections of roof where each string of panels will output power at different times across the day. By splitting the panels like this, the output of solar power gets distributed across the day, making it easier to use more of the solar power because there isn’t such a big peak in the middle of the day:
The other point that can influence the decision of where to install panels is that time-of-use tariffs can sometimes be charged by your energy retailer (ask us for help if you are not sure about this). This typically will only apply to households in the Ausgrid distribution area (roughly the eastern half of Sydney):
A solar system will peak when the sun is shining directly onto the panels, so for an array facing north, this will be for approximately 4 hours during the middle of the day.
The graph below shows a system that is installed on a roof facing north-west where there is a bit of early morning shade. This is a great orientation for a solar system in Sydney, especially if you have time-of-use billing where power is most expensive after 2pm on weekdays in summer. You can see in the graph how even in autumn the system will continue operating until 7 pm if you have the panels installed on a roof that catches the late afternoon sun:
The other important point to take away from this image is that a 5kW system will almost never reach its peak output. This system reached a maximum output of 3.84 kW and yet produced 29.1 kWh of power across the day:
For a 5kW system to output close to 5kWs at any one time, it has to be the right time of the day and the right time of the year, which is very rare. In this example, the system is installed on a tile roof with a normal pitch of about 20 degrees. There are 19 panels all facing north-west. This helps extend the output into the late afternoon, as seen in the graph above. In Sydney during summer, panels that are installed flat will be working closer to their peak efficiency because the sun is so high in the sky.
The peak output on this system during a sunny March day is only 3.84 kW, however, even in March, this 5kW system will typically produce around 30 kWh a day, much higher than the Clean Energy Council guideline of 19.5 kWh.
For more information, please contact the Solaray Team today. We can help you design a system that makes the most of your roof and your energy consumption patterns: