Why Do Homes with Solar Panels Still Lose Power?

A review of the Spanish blackout

On April 28, 2025, Spain suffered a rare large-scale blackout, plunging the country into darkness for 11 hours, paralyzing traffic, disrupting communications, and stranding tens of thousands of people. This catastrophic blackout occurred just six days after Spain had celebrated its national grid running "on 100% renewable energy for the first time on a weekday." What was particularly shocking was that many households with solar panels were also not immune to the blackout.

Limitations of Photovoltaic Systems

When you have a photovoltaic system with only solar panels installed in your home, a paradoxical but very important situation occurs when a blackout occurs: even if your solar panels are working and the sky is clear, your house will be without power. Why is this?

Yes, it is due to European safety regulations that all solar inverters connected to the grid must detect the loss of voltage and shut down immediately, which is called anti-islanding protection.

The reason for this "blackout" is to protect grid maintenance technicians: if thousands of homes feed power into a "dead" grid, it could be fatal for the workers who are repairing the fault. Therefore, if you only have solar panels connected to the grid, you will not be able to use electricity during the blackout. Your solar panels will automatically disconnect.

Energy Storage Batteries: A Key Solution for Home Energy Security

The solution: use batteries. If you also have batteries, the situation is different, although here it depends on the type of inverter you have and its configuration. If you have a hybrid inverter (solar + battery), some modern inverters already allow continued operation in the so-called island mode or backup mode. This means that when they detect a power outage, they physically disconnect from the grid and power your house using only the solar energy and the energy stored in the battery.

In addition, there are backup inverter systems, where a separate system is used to power a specific part of the house (for example, the refrigerator, basic lighting or the internet).

But even so, to make this all work properly, you need appropriately sized lithium-ion or lead-acid batteries, a hybrid inverter compatible with island mode operation or an inverter with backup function, and an automatic disconnect relay system to separate your house from the public grid in the event of a power outage to ensure safety.

For ordinary families, the lesson from Spain is clear: in the context of intensified climate change, more extreme weather, and increased pressure on the power grid, energy security cannot be completely outsourced to the public system, and each family needs to consider a certain degree of energy self-sufficiency. Even relatively small-scale investments can provide valuable power guarantees in times of crisis. With technological advances and economies of scale, the economics of these systems will continue to improve.