What Happens to Solar Panels During Power Outages?
Why on-grid solar switches off during a power cut even in bright sun, how anti-islanding protects line workers, and your options for backup power with solar.
It surprises many new solar owners: the power goes out on a bright sunny afternoon, and the solar system on the roof stops working too. This is not a fault — it is a deliberate safety feature. Here is why it happens, and what your options are if you want power during outages.
The short answer
- On-grid systems: switch off automatically during a power cut, even in full sunshine.
- Hybrid systems with a battery: keep selected circuits running during an outage.
- Off-grid systems: are unaffected by grid outages, because they never rely on the grid.
Why on-grid solar switches off: anti-islanding
When the grid fails, technicians go out to repair the lines. If your solar system kept pushing power into those lines, it could electrocute someone working on a line they believe is dead.
To prevent this, every grid-connected inverter has anti-islanding protection. It constantly monitors the grid. The moment the grid's voltage or frequency disappears, the inverter disconnects within a fraction of a second. When grid power returns and stays stable, the inverter reconnects automatically after a short delay.
This is a mandatory safety requirement for grid connection, not an optional setting.
Can I just keep using solar power in my home during an outage?
Not with a standard on-grid inverter. It needs a stable grid signal to operate. Without that reference, it cannot safely run your home loads by itself.
To use solar power during outages, you need a system designed to create its own isolated power supply — which means a battery and a hybrid inverter.
Option 1: Hybrid solar with a battery
A hybrid system detects the outage, disconnects from the grid safely, and powers your essential loads from the battery and panels.
What it can run: usually a backup circuit covering lights, fans, a fridge, Wi-Fi and phone charging. Heavy loads like air conditioners and geysers need a much larger battery.
Things to know:
- Battery capacity decides how long backup lasts.
- Panels recharge the battery during the day, even during an outage.
- Adds significant cost compared with on-grid.
Option 2: Keep your existing inverter-battery backup
Many homes already have a conventional inverter with batteries for power cuts. It can continue to work alongside an on-grid solar system:
- Solar reduces your daytime bill through net metering.
- Your existing inverter handles backup during outages from the grid-charged battery.
This is often the most cost-effective approach if you already own a working backup inverter.
Option 3: Off-grid solar
Off-grid systems are not connected to the grid, so outages do not affect them. They are best for locations without a reliable grid connection, but are more expensive and not eligible for the residential subsidy. See On-Grid vs Off-Grid vs Hybrid.
Which option makes sense for you?
| Your situation | Best option |
|---|---|
| Outages are rare and short | On-grid, no battery |
| You already have an inverter-battery | On-grid + keep existing backup |
| Frequent or long outages | Hybrid with battery |
| No grid connection available | Off-grid |
Frequently asked questions
Why did my solar system stop working when the power went out?
Your on-grid inverter disconnected automatically because of anti-islanding protection. It prevents your panels from sending power into grid lines that repair crews may be working on, and it reconnects once grid power is restored.
Does solar work during load shedding?
A standard on-grid system does not. A hybrid system with a battery does, running your backup circuits from stored and solar power during load shedding.
Can I use my old inverter battery with solar panels?
Your existing backup inverter can keep working alongside an on-grid solar system for outages. Connecting an old battery directly to a new solar system requires compatible equipment, so ask your installer before attempting it.
How long will a solar battery run my home during an outage?
It depends on battery capacity and what you run. A modest home battery can keep lights, fans, a fridge and Wi-Fi going for several hours. Running air conditioners requires much larger and more expensive storage.