Winter has a way of making solar panels look like they've gone on holidays. The skies turn grey, the days get shorter, and it's tempting to assume your system has taken a break along with the warm weather. It hasn't. But there are a few things worth understanding about how your system behaves this time of year, and what to actually watch for.
Solar Panels Run on Daylight, Not Sunshine
This is probably the most common misunderstanding we come across during the cooler months. Solar panels generate electricity from daylight, not from direct sunlight. On a heavy overcast day your output will drop, sometimes noticeably, but the system keeps working. The panels are still converting available light into electricity. They're just working with less of it.
Photovoltaic panels respond to the full spectrum of visible light, which is present even when the sky is completely covered. A thick bank of storm cloud will cut into that significantly. A typical winter overcast won't stop your system from generating altogether. If you're checking your monitoring app on a grey morning and seeing some output, that's normal. That's your system doing what it should.
What's worth noting is that cool temperatures can actually be beneficial for panel efficiency. Solar panels, like most electronics, perform better when they're not cooking in 38 degree summer heat. So while you might generate less in winter due to reduced daylight hours and lower sun angles, the panels themselves are often running at their best in the cooler conditions Adelaide winters bring.
The Bigger Factor in Winter Is the Sun Angle
Cloud cover gets a lot of the blame in winter, but the more significant factor affecting Adelaide solar output from June through August is the position of the sun in the sky. During winter, the sun tracks lower across the northern horizon rather than climbing high overhead as it does in summer.
For north facing panels at a reasonable tilt, this is actually fine. The sun's lower angle means it hits north facing panels quite directly during the middle of the day, particularly around solar noon. If your system was designed with Adelaide's conditions in mind, which it should have been, your north facing panels are well positioned for this.
Where it gets interesting is with shading. The lower winter sun angle creates shadows from trees, rooflines, chimneys, and neighbouring structures that simply didn't exist in summer when the sun was higher. Something that cast no shadow on your panels in December may be shading them significantly in June. The sun is coming from a different angle now.
This is one of the more overlooked causes of unexpected performance dips in winter. It's worth walking around your property on a clear winter day and having a look at what the panels are sitting in the shadow of around 10am and 2pm.
Trees Are a Seasonal Variable Worth Checking
Adelaide and the Hills have a lot of beautiful trees. They also grow. And unlike the fixed structures on your property, trees change throughout the year. Deciduous trees that shed their leaves in autumn give your panels a clear run through winter, which is helpful. But eucalypts and other natives don't work that way, and even deciduous trees get taller year on year.
The most common situation we see in winter is panels being partially shaded in the early morning or late afternoon by growth that has happened gradually over time. Because it's gradual, it can be easy to miss. You might notice your output has been a little off without being able to pinpoint why.
If trees are an issue, it's worth looking at this sooner rather than later. Even partial shading on one or two panels can have a disproportionate effect on the output of the whole system depending on how your inverter and panels are configured. A small amount of shade at the wrong point in your array can drag the whole string down.
How to Read Your Monitoring App This Time of Year
Most modern solar systems come with monitoring apps or dashboards that let you see how your system is performing in real time and historically. If you're not using yours regularly, winter is a good time to start paying attention.
A couple of things to look for. First, check your output around solar noon on a clear winter day. This is when your system should be at or near its daily peak. Comparing that figure to a clear summer day will show you the natural seasonal difference, which is expected and normal. The sun is up for fewer hours and sits lower in the sky.
Second, look for consistency. If your output is dropping significantly on days that look clear and sunny from the ground, that's a more interesting data point than a drop on an overcast day. A consistent and unexplained underperformance on good days is worth investigating. It could be shading, a faulty panel, an inverter issue, or something else. It's the kind of thing that's better caught early.
A drop on heavy overcast days is completely normal. A consistent drop on clear days is not something to just accept and move on from.
When to Pick Up the Phone
Most of what you'll see in winter is perfectly explainable and nothing to worry about. Output is lower because daylight hours are shorter and the sun sits lower. That's physics, not a fault.
But if something doesn't look right, it's worth getting it checked. Fault codes on your inverter, a system that's generating nothing on a clear day, or a consistent unexplained drop in output compared to what you'd expect are all worth a conversation. The sooner a fault is identified, the sooner it's fixed, and the less generation you lose in the meantime.
We've been working with solar systems across Adelaide and the Hills since 2009. We know what normal looks like for this region in winter, and we're happy to take a look if something seems off. A quick call is often all it takes to work out whether there's actually a problem or whether what you're seeing is completely expected for this time of year.
Winter solar is one of those things that looks more complicated than it is once you understand the basics. Your system is still working. The sun is still there, even when it doesn't feel like it. And if you've got questions about what you're seeing on your monitoring app, we're always happy to help you make sense of it.
Get a free solar quote from Track Energy. Visit trackenergy.com.au or call 0416 533 628
