One of the most common reasons people hesitate on solar is the weather. "But we get a lot of cloudy days" — we hear this especially from Melburnians. The good news: your panels don't need direct sunlight to generate electricity. They just need light.
How Solar Panels Actually Work in Clouds
Solar panels capture light, not heat or direct sunlight. They generate electricity from both direct sunlight and diffuse light — the scattered light that makes it through clouds and illuminates everything on an overcast day.
The output varies depending on the cloud type:
- Light or broken cloud: 70–90% of a clear-day output. You'll barely notice the difference.
- Heavy uniform overcast: 25–50% of rated output. Your system is still generating meaningful electricity.
- Thick storm cloud: 10–25% of rated output. Output drops significantly, but it's not zero.
The Melbourne Myth
Melbourne is often used as the argument against solar in Australia. But Melbourne still gets plenty of solar hours — the average is around 4.1 peak sun hours per day annually, compared to Perth's 5.5. A 6.6kW system in Melbourne generates roughly 22–25 kWh/day on average across the year, less than Brisbane or Perth but still enough to meaningfully offset most households' bills.
The reason Melbourne solar still pays back well is that Melbourne electricity prices are high. Every unit you self-consume saves you 30+ cents. The lower generation is offset by the high value of what you do generate.
One Thing Clouds Actually Help With
Extreme heat reduces panel efficiency. Panels are rated to perform at 25°C — on a 40°C Melbourne summer day, you'll see a minor dip in output. Partly cloudy days in the 20–25°C range are often close to optimal operating conditions, because the panels are cool but light intensity is still high.
What About Rain?
Rain itself doesn't help or hurt output much — though light rain on an overcast day means low output. One actual benefit: rain cleans dust and grime off your panels, which can meaningfully improve efficiency. Australia's dusty inland regions can see panels lose 3–5% output from dust buildup. A good rainy day is a free panel clean.
The Bottom Line
If you live somewhere with frequent overcast weather, size your system slightly larger than a pure consumption-matching calculation would suggest. The extra panels don't cost much at the margin, and they compensate for lower output on cloudy days.
No matter where you live in Australia, solar is almost certainly worth it. Want to know your specific numbers? Upload your bill to GridBeater and we'll calculate your savings based on your location's actual solar irradiance data.
See your personalised solar savings estimate → Free at GridBeater