Yes, solar panels work on cloudy days. Under heavy cloud they still make about 10 to 25% of their rated output, and under light cloud they can reach 50 to 70%. Panels run on light, not heat, and Cairns gets plenty of light even when the sky is grey.
We install solar across Cairns and Far North Queensland, from Port Douglas to the Atherton Tablelands to the northern beaches. This is the question we get asked more than any other, because our wet season runs November to April. Here is the honest answer, with real numbers.
Quick answer
- Panels still produce 10 to 25% of rated output under heavy cloud, and 50 to 70% under light cloud
- Rain does not damage panels. It actually cleans them for free
- Panels lose about 0.3 to 0.4% of output for every degree above 25 C, so heat costs you more than most people think
- A Cairns 6.6 kW system averages roughly 26 to 30 kWh a day across the whole year, wet season included
- The real long term enemy in the tropics is grime and mould, not clouds
How do solar panels make power when it is cloudy?
Solar panels turn light into electricity. Not heat. Light.
On a clear day, most of that light comes straight from the sun to your roof. On a cloudy day, the light scatters through the clouds and arrives from all directions. This is called diffuse light, and Cairns has a lot of it. Even under a thick grey sky, there is enough light bouncing around to keep your panels producing.
Think about a cloudy day at the beach. You can still get sunburnt. The energy is still coming through, just spread out. Your panels catch that same spread out energy.
Modern panels are much better at using diffuse light than the panels of ten years ago. The panels we install from SunPower are built to pull useful power from low light conditions. If you want the full picture of how the technology works, our guide on how solar panels work walks through it step by step.
So the short version: clouds reduce output. They do not stop it.
The surprising part: heat hurts panels more than clouds do
Here is the fact that surprises almost every Cairns homeowner we talk to. Solar panels are less efficient when they get very hot.
Panels are tested at 25 C. For every degree above that, a typical panel loses about 0.3 to 0.4% of its output. On a scorching Cairns day, the panel itself can sit well above 60 C on your roof. That can quietly shave a meaningful slice off production.
Now flip it around. A mild overcast day keeps the panels cool. Cool panels work closer to their rated efficiency. So a soft grey day can sometimes out-produce what you would expect, and the gap between a hot clear day and a mild cloudy day is smaller than most people assume.
This is one of the reasons solar makes so much sense here despite the wet season. We covered the heat side in detail in our guide to solar panel efficiency in tropical climates, and it changes how we design systems for FNQ roofs.
Do solar panels work in the rain?
Yes. Output drops while the rain is falling, because rain clouds are thick. But the rain itself does something valuable. It washes your panels.
Dust, bird droppings, salt from the sea breeze, and mould spores all land on your panels over time. Every bit of that blocks light. A good wet season downpour rinses a lot of it off for free.
We see this in the monitoring data all the time. A system limps a little through the dusty end of the dry season, then a big rain comes through and output steps up on the next clear day. The rain did the cleaning.
Rain does not get into the panels. Panels are sealed units built to sit outside for decades. They handle rain the way your roof handles rain, which makes sense, because they are part of your roof. Our post on how long solar panels last covers what actually wears them out, and rain is not on the list.
What does a Cairns wet season day really look like?
Numbers beat guesses. Here is what a typical 6.6 kW system in Cairns produces under different skies.
| Weather | Typical daily output (6.6 kW system) |
|---|---|
| Clear dry season day | 30+ kWh |
| Light cloud | 18 to 25 kWh |
| Grey wet season day | 8 to 15 kWh |
| Heavy storm day | 5 to 10 kWh |
The wet season days sting when you look at them alone. But solar is a yearly game, not a daily one. Cairns averages about 5 peak sun hours a day across the year, and the dry season is so strong that a 6.6 kW system still lands at roughly 26 to 30 kWh a day averaged over 12 months.
At Ergon tariff 11 rates of roughly 30 to 35 cents per kWh, every one of those kilowatt hours you use yourself is real money. Even a grey day making 10 kWh is covering around $3 of grid power. The maths across a full year is what matters, and we ran that maths in our post on whether solar is worth it in Queensland.
How we design Cairns systems for the wet season
A system designed for Brisbane weather will disappoint you in Cairns. Here is what we do differently.
We size 20 to 30% above your bill. If your usage says you need a certain size, we quote bigger. The extra capacity means that even on a grey February day, the system still covers most of your daytime use. On clear days the surplus goes to the grid at the 6.006 cents per kWh feed-in rate, or into a battery where it is worth far more. Our guide on how many solar panels you need explains the sizing logic.
We look at east west splits. Wet season storms in Cairns love the afternoon. A north only array peaks at midday. Splitting panels across east and west faces catches strong morning sun before the clouds build, and spreads production across more of the day. Whether that suits your home depends on your roof, which is exactly what we assess in our roof suitability guide for Cairns.
We plan for blackouts. The wet season overlaps cyclone season, and storms take the grid down. A battery keeps your fridge, fans and lights running when the street goes dark. We install Tesla Powerwall 3, BYD, Sigenstor and Fronius battery systems, and the federal battery rebate currently takes about 30% off an installed battery, around $252 per usable kWh for the first 14 kWh under the tiered scheme that started 1 May 2026. We wrote a full piece on running a solar battery through cyclone season if backup power is your main worry.
We set up monitoring on every job. As a Fronius Partner Plus dealer, we set up monitoring so you can watch a storm front roll through on your phone and see exactly what it does to output. It turns the cloudy day question from a worry into a graph. Our Fronius Solar.web guide shows you how to read it.
Wet season myths, sorted
Myth: panels stop working in rain. No. Output drops, production continues. The table above shows even storm days produce 5 to 10 kWh on a 6.6 kW system.
Myth: rain damages panels. No. Panels are sealed, weatherproof units. Rain cleans them.
Myth: cyclones will rip panels off the roof. Cairns sits in cyclone region C, and every system we install uses cyclone rated mounting engineered for that. A properly mounted array is one of the more secure things on your roof. We went deep on this in our guide to cyclone proof solar in Cairns.
Myth: cloudy weather means solar is not worth it in the tropics. Cairns averages about 5 peak sun hours a day across the year. That is a strong solar resource. The wet season is already baked into every payback number we quote.
What actually hurts output in the tropics
It is not clouds. Clouds come and go. The real long term drag on a Cairns solar system is buildup.
Humidity and warmth make FNQ a paradise for mould. Add dust, salt spray on the northern beaches, and bird droppings, and a neglected array can quietly lose a chunk of its output year after year. The owner never notices, because the drop is gradual.
That is fixable. Our solar maintenance service cleans the array and checks the hardware, and a solar health check tells you exactly what your system is producing versus what it should be. If your output looks low and you are not sure why, start with our troubleshooting guide for Cairns solar systems.
A cleaned, healthy system on a grey day will often beat a grimy system on a clear one. That is the tropics in one sentence.
FAQ
Do solar panels work on cloudy days in Cairns?
Yes. Under heavy cloud a system still makes about 10 to 25% of its rated output, and under light cloud 50 to 70%. Panels run on light, and Cairns has strong diffuse light even when the sky is overcast.
How much power does a 6.6 kW system make on a wet season day?
A grey wet season day typically delivers 8 to 15 kWh, against 30 plus kWh on a clear dry season day. Averaged across the whole year, a Cairns 6.6 kW system still lands around 26 to 30 kWh a day.
Does rain damage solar panels?
No. Panels are sealed units designed to live outdoors for decades, and our mounting is rated for cyclone region C. Rain actually helps by washing dust, bird droppings and mould off the glass for free.
Should I get a battery for the wet season?
If blackouts worry you, yes. Storms and cyclones take the Cairns grid down most wet seasons, and a battery keeps essentials running. The federal rebate currently cuts about 30% off an installed battery, which has changed the maths for a lot of our customers.
Talk to a local who has seen every wet season
We are G-Solar & Electrical, based at 32 Magazine Street in Stratford. Grant Newman, our owner, is a fifth generation Cairns electrician and SAA accredited, so wet season design is not theory to us, it is home. You can see our recent installs across FNQ on our work page, and our 326 Google reviews sit at a 5.0 rating.
If you want a residential solar system designed for real Cairns weather, not brochure weather, get a free quote here. We also offer payment plans through Handypay. We will size it for the wet season, mount it for cyclone country, and show you the live numbers on your phone.