How does weather affect solar panel output?

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Solar panel production can vary significantly based on weather conditions. For example, production can be 20-30% higher on a sunny day than the predicted average output. During bad weather, such as rain and clouds, the productivity level significantly decreases. In fact, it can be as low as 10% or on average around 20-30%.

A solar panel system's size and the use of battery storage can help ensure a consistent electricity supply on rainy days. To find the best solar panel system and battery storage, it is advised to talk to a local supplier or installer.

Will the weather affect my solar panel output?

You might wonder how the weather can affect your solar production when it is cloudless and sunny versus when it’s overcast or even a rainy day.

Firstly, to get an overall idea of what a particular sized solar system can produce in a specific location, you check out our output calculator on our website, enter your postcode and system size, and the calculator will give you an expected output yearly and monthly solar system generation output in kWh.

Many of you who have purchased a residential or commercial solar system will have been supplied with an annual system power output estimate via the installation company.

The system calculates its output based on the number of hours of sunlight in a specific area for the year. It uses weather data from nearby stations over the past ten years to estimate an average for the year.

These estimates also apply to monthly output. However, it is not possible to accurately predict the exact solar output for a specific date. Nevertheless, over time they are usually quite accurate.

Solar panel affected on a sunny day with rain droplets
Weather can obviously have a large effect on solar efficiency

In the past five years, it rained on April 1st in Townsville. However, this does not guarantee that it will rain on April 1st this year. So, the likely predictions of solar output rely on a mix of variable weather conditions, from bright and sunny to overcast days.

Solar output calculator

So if you seek the most likely output for your system month by month – try our output calculator.

The calculator predicts the energy output of a 6.6 kW system in Brisbane for March. It estimates 30.4 kWh for the month. However, it does not specify the energy production for sunny and rainy days. So, the question remains: how much energy will the system generate on a sunny day compared to a rainy day?

In my experience, watching the performance of many systems via detailed monitoring software such as Solar Analytics, on a sunny day, you would expect to add another 20 to 30% to this 30kWh number, meaning on a clear sky, below 25 degrees day, you could generate as much as 40-plus kWh.

On a rainy and cloudy day, system production decreases to only 10% during a severe thunderstorm with dark clouds. Still, usually, 20-30% of the predicted average output is what will be achieved.

In numbers, this means instead of producing 40kWh plus on a sunny day, as per the sample above, one will potentially have to contend with an overall production of around 10kWh on a rainy and cloudy day.


A strong solar PV system can produce 30 kWh of energy on sunny days. This amount of energy is enough to generate up to 160 kWh for essential needs. But when overcast skies temper production, dropping to a minimum of 30-40 kWh, can your current setup keep up? This is where battery storage becomes a game-changer.

For those with large solar systems, rainy-day production may not fully satisfy demand. A strategic battery bank stores extra energy from sunny days to use when there is less energy being generated. This ensures seamless energy availability, regardless of weather conditions.

Think of it as an investment in future-proofing your energy independence. By harnessing the sun’s bounty on clear days and strategically utilising stored energy on overcast ones, you’re minimising reliance on the electrical grid and maximising the return on your solar investment.

Our FAQs provide answers to important questions about solar batteries. These questions include information about capacity, lifespan, and cost. By reading our FAQs, you can make informed decisions for your solar system.

Explore our battery storage options and unlock the full potential of your solar investment.

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