Which way to face solar panels in Australia

Which way should fixed panels face in Australia?

North. Fixed panels in the southern hemisphere are normally tilted and pointed due north.¹ The reason is where the sun travels. The Your Home guide, which is about orienting houses rather than solar panels, says the path of the sun in Australia is to the north.²

In winter the sun rises in the north-east and climbs only to a low angle in the north.³ So a north-facing panel is pointed at the middle of that path.

Is true north the same as the north on my compass?

No, and it catches people out. A compass shows magnetic north, and solar north is not the same thing.² That guide is written for houses, not panels, but the point about the two norths still holds. The advice that fixed panels face due north comes from the photovoltaic system source above.¹

How far apart the two norths are depends on where you live. The government guide says solar north can be significantly different from magnetic north.² So don't set a frame by a camping compass and call it done.

Phones are a better start. Google Maps and most smartphones use solar north by default, but the guide suggests checking your settings.²

How do I find true north on my block?

Use the sun itself. Stand a vertical stick in the ground at solar noon, when the sun is at its highest. South of the Tropic of Capricorn, that noon shadow always points south.³ Stand with your back to it and you're facing north.

The Tropic of Capricorn sits at about 23.4° south.³ If you live further north than that line, the shadow trick doesn't follow the same rule, so lean on a map app or a printed sun chart instead.

There's a second check. At the equinoxes, in March and September, the sun rises due east and sets due west almost everywhere.³ Mark those two points on the horizon and you've got east and west.

What if my roof faces another way?

Some roofs do. You've got three options.

• Mount the panels on the roof as it is, and accept a lower output.
• Fit a tilted frame so the panels point north, even though the roof doesn't.
• Put the panels on a ground frame somewhere clear.

How much you lose depends on how far from north you are, and on your tilt and location.¹ These notes don't give a percentage for an off-north roof, because the sources don't. Ask an installer for a modelled figure for your address.

One thing helps your case. A flat panel is fairly tolerant of being out of line with the sun: even a 25° miss costs less than 10% of the direct light.⁴ That figure is about the sun's angle, not roof direction, so treat it as a sign that small errors are forgiving, not as a promise for any roof.

Do all the panels have to face the same way?

If they're wired together into one string, they should. A string works best when it's made of similar panels pointing the same way, square-on to the sunlight.⁵ Keep each group pointing one direction.

Who does the wiring?

Pointing panels north is a mounting job. Connecting them is different. In Australia, fixed mains wiring, switchboards and grid connection are licensed electrical work, not DIY. Any job that connects or disconnects battery, fuse, shunt or inverter cables needs the battery isolated first and the maker's manual followed. If you're unsure, hire a licensed electrician.