Will a Solar Plant Operate During a Power Outage?

A common misconception about solar energy is that if you have solar panels on your roof, your home will stay powered during a blackout. Unfortunately, that’s not always the case. If you're considering solar — or already have a system installed — it's essential to understand how different types of solar setups behave when the grid goes down, and what backup options are available to keep your home running.

Why Grid-Tied Solar Goes Dark in a Power Outage

Most residential solar installations in Portugal are grid-tied systems. These connect directly to the utility grid and work by feeding solar energy into your home and exporting excess power to the electrical network.

However, during a power outage, these systems automatically shut down to prevent any electricity from flowing back to the grid.  This is a safety feature called anti-islanding protection and is a safety feature to prevent workers on the line from being electrocuted during a power outage. This means that even with bright sunlight, your solar system won’t power your home unless it includes a backup solution.

Your Options for Backup Power

To stay powered during a grid failure, you’ll need a solar system that includes battery storage and the right inverter configuration.

Here are your main options:

1. Hybrid Inverter + Battery System

Hybrid inverters allow solar panels to charge a battery, which can then power the home when the grid is down.

• Examples: Huawei SUN2000 with LUNA battery, FoxESS with FO battery
• Switching: Automatic in most setups
  
• Limitations: Usually only powers "critical loads" like lighting, fridge, internet, etc.

These systems often require a dedicated backup circuit or load panel and, with Huawei, require a transfer switch to transfer power during an outage.

Fox ESS Hybrid Inverters

FoxESS hybrid inverters come with an EPS (Emergency Power Supply) output which provides backup power automatically during a grid outage. When paired with a Fox battery and correctly installed, the EPS can seamlessly supply power to essential circuits like refrigeration, lighting, and internet.

• Switching: Automatic when configured with EPS
  
• Limitation: EPS usually only supports critical loads, not the entire home

It's important that your installer wires a dedicated critical load panel for the EPS to function properly.

2. Tesla Powerwall

The Tesla Powerwall is one of the most seamless solar backup solutions on the market.

• Automatic switching via the Tesla Backup Gateway
  
• Powers critical or entire home loads depending on the number of Powerwalls
  
• Solar panels continue to charge the battery during outages
  

Limitations: Higher upfront cost and may require multiple units for large homes.

3. Manual Generator (Non-Solar)

Diesel or gas generators can also provide emergency power.

• Effective for long outages
  
• Not sustainable or clean
  
• Requires manual start-up and fuel storage
  

How Much of Your Home Can You Back Up?

It depends on your system size and setup:

Questions to Ask Your Installer

Before installing or upgrading your solar system, ask:

• Is this a hybrid inverter that supports battery backup?
  
• Do I need a separate backup/load panel?
  
• Will the system switch over automatically during an outage?
  
• Can I expand the system in the future?

Final Thoughts

A standard solar setup alone won’t keep your lights on during a power outage. To enjoy true energy independence, you need the right combination of inverter, battery, and backup configuration.

At Sol Viva, we help international homeowners in Portugal choose solar systems that are resilient, cost-effective, and future-ready.

Ready to make sure your home stays powered even when the grid goes down?

Contact us or book a slot to talk.