Your solar system performs well under clear skies, but what happens when the rain comes?
Check your monitoring app and you’ll see the numbers drop as thick clouds move overhead. With a 6.6 kW, 10 kW or larger system on the roof, seeing only a fraction of that capacity can easily make you wonder how much power your panels are producing.
Your panels can still generate electricity from the diffuse sunlight that reaches them through cloudy skies, but their output will drop as less sunlight reaches the panels. If that reduced output can’t cover the electricity you’re using at home, you’ll draw the remaining power from the grid or your battery.
Rainy-Day Performance for Different Solar System Sizes
The number attached to your solar system tells you its rated power-generating capacity. It doesn’t tell you how much electricity the system will generate throughout a rainy day. That electricity is measured in kilowatt-hours (kWh), and the amount you get changes with the sunlight available to your panels throughout the day.
Cloud cover can change throughout the day, while your location, season, panel direction, shading and other conditions also affect generation. More installed capacity gives you more generating capacity to work with, so let’s look at what rainy weather can mean for some common solar system sizes.
3 kW Systems Have Less Capacity to Work With
Your 3 kW solar system will still generate electricity under cloudy skies, but its output can rise and fall as conditions change throughout a rainy day.
With less generation available, running several appliances at once can push your household electricity use above what your panels are producing. When that happens, your home draws the remaining electricity from the grid or your battery if you have one. The battery size determines how much stored energy you have available when solar production drops.
On rainy days, keep an eye on your monitoring app and avoid running several high-use appliances at the same time when solar generation is low.
5 kW Systems Depend on Household Demand
A 5 kW system gives you more generating capacity, but that doesn’t tell you how much of your household electricity use solar will cover during the rain. Two homes with the same 5 kW system can have very different results on the same rainy day.
| Home Using Less Electricity | Home Using More Electricity |
| Only a few appliances are running. | Air conditioning, kitchen appliances or other larger loads are running. |
| Available solar covers more of the home’s electricity use. | Available solar covers less of the home’s electricity use. |
| Less electricity needs to come from the grid. | More electricity needs to come from the grid when demand exceeds solar generation. |
This is why your monitoring data matters. Instead of focusing only on how far generation has dropped from 5 kW, compare how much solar you’re generating with how much electricity your home is using. This gives you a clearer picture of how rainy weather is affecting your grid use.
6.6 kW Systems Often Use a 5 kW Inverter
Many 6.6 kW solar systems in Australia use a 5 kW inverter. The 6.6 kW refers to the combined rated capacity of the panels, while the inverter converts the DC electricity they generate into AC electricity for your home.
During rainy weather, less sunlight reaches the panels, so their output can sit well below their rated capacity. Seeing less than 5 kW on your monitoring system during these conditions doesn’t automatically mean the inverter is limiting your solar generation. Your panels might simply not be producing enough power for the inverter to reach that level.
Check the weather and compare the result with your normal generation pattern before treating lower rainy-day output as a system problem.
8 kW Systems Can Support Larger Daytime Loads
The 8 kW system gives you more capacity to run larger daytime loads from solar, but rainy weather can change how much of that capacity is available.
Appliances such as air conditioners, clothes dryers, dishwashers and pool pumps can use a substantial share of your solar generation when several are running at the same time.
On a rainy day, check your solar generation before switching on several larger loads. If generation is low, spreading those loads across the day can reduce how much electricity you need from the grid. When conditions brighten and solar output increases, that can be a better time to run flexible loads.
10 kW Systems Still Lose Output in Heavy Cloud
A 13 kW or larger system gives you more generating capacity, but rainy weather can still leave several large household loads competing for the solar electricity available. On lower-generation days, pay closer attention to when you:
- Charge your EV: Moving charging to a brighter part of the day can help you use more solar.
- Run air conditioning: Avoid running heating or cooling alongside several other high-use appliances when solar output is low.
- Heat water: Schedule electric water heating for periods when your solar generation is higher.
- Run pool equipment: Run your pool pump when your panels are producing more electricity.
- Charge your battery: Understanding how solar batteries work can help you get more from periods of higher solar generation by storing excess electricity for later use.
On rainy or changeable days, avoid stacking several high-use activities into the same period. Spread flexible loads across the day and prioritise them when more solar electricity is available.
What Happens to Your Solar Panels After the Rain
Once the rain stops and the clouds start to clear, your solar system responds to the changing conditions. Here’s what can happen:
✓ Solar generation increases as stronger sunlight returns and cloud cover clears.
✓ Rain can wash loose dust and surface dirt from your solar panels.
✓ Some dirt can remain after rain depending on the type of soiling and panel angle.
✓ Your solar panels resume normal generation as sunlight returns.
If dirt remains after the rain, particularly in dusty conditions, it can continue to reduce how much sunlight reaches the panel surface. Have the panels professionally cleaned if the buildup remains and avoid climbing onto the roof to clean solar panels yourself.
Solar Generation Continues Even on Rainy Days
Rain doesn’t switch your solar system off. Your panels can still generate electricity from the sunlight reaching them through cloudy skies, just at a lower output than under stronger sunlight. Once the clouds clear, generation can rise again. So, a drop in output during wet weather is part of normal solar performance and doesn’t automatically mean something is wrong with your system.
