The recent massive blackout in Spain and parts of Europe has made clear a reality that many solar system owners did not know about: having solar panels does not guarantee that you will have electricity during a power cut. At Atodosol we have been warning about this for years and offering effective solutions. Find out why this happens and how you can protect your home against future blackouts.
Why do solar panels also disconnect during a blackout?
Contrary to what many owners expected, their solar systems stopped working instantly during the massive blackout in Spain on 28 April 2025. This situation, far from being a technical fault, is a mandatory safety mechanism built into every grid-tied solar installation in Spain.
The legal safety mechanism that left thousands of solar homes in the dark
Spanish electrical safety regulations (RD 1699/2011 and later updates) state that standard solar inverters must automatically disconnect when they detect that the grid is missing. This requirement, known as "anti-islanding", is designed to protect technicians working on line repairs, preventing private solar systems from injecting electricity into the grid during an outage.
This protection, while necessary, has a direct consequence for users: no matter how sunny the day is and how much energy your solar panels are generating, you will not be able to use it during a blackout if you do not have the right backup systems in place.
The difference between generating energy and being able to use it during a blackout
During the blackout, many owners asked themselves: "If my panels are getting sun, why can't I use that electricity?"
Conventional inverters: designed to disconnect
The standard inverters installed in most solar systems have one main job: convert the direct current generated by the panels into alternating current usable in the home, and synchronise it with the grid. However, these inverters lack the ability to operate independently when the grid fails.
Why your panels work but you cannot use their energy
During the 28 April blackout, your solar panels were still capturing solar radiation and generating electricity, but the inverter, on not detecting the grid signal, automatically shut down as a safety measure. That means that valuable energy could not be tapped precisely when it was needed most.
Solutions that make the difference: Backup Box and battery systems
At Atodosol we have been pushing solutions for years that guarantee continuity of supply even during long blackouts.
Backup Box: a small investment that delivers 100% continuity
The Backup Box system is a relatively cheap solution that does not represent more than 5% of the total cost of a solar installation.
This device lets your photovoltaic system keep working during a power cut, using in real time the energy your solar panels are producing (as long as there is sun).
How does it work? The Backup Box creates a small isolated grid inside your home, allowing the inverter to run in "island mode" during a blackout. That means you can keep using the electricity generated by your solar panels to power essential appliances and devices, as long as there is sun and your panels are generating energy.
Battery systems: complete energy independence with available subsidies
For those looking for a more complete solution, battery storage systems offer total energy independence. Although they represent a more significant investment (up to 50% of the installation cost), they let you store surplus energy during the day to use it whenever you need it most, including at night or on cloudy days.
The good news is that these systems currently come with significant subsidies and government aid that can substantially cut the upfront cost. In the current context, with the growing instability of European electricity grids, this aid reflects the strategic importance authorities place on household energy resilience.
A real case: when planning ahead makes the difference
During the recent national blackout, while millions of homes were left in the dark, some families carried on with life as normal thanks to solar backup systems.
The Atodosol case: technology in action during the crisis
On the day of the blackout, Roberto, founder of Atodosol, was able to film how his solar system with backup-transfer inverters kept working perfectly. Two electric vehicles charging simultaneously, the swimming pool heating running. The inverters generating an average of 9 kW each.
This is not an isolated case or a special installation: it is just one of the same systems Atodosol offers all its clients, with the difference that Roberto chose to include the backup component, an option many clients unfortunately turn down considering it unnecessary... until a blackout happens.
Decisions that make the difference
The recent blackout experience has shown that seemingly small decisions, like investing in a backup system that represents no more than 5% of the total budget, can make a radical difference in emergency situations.
Having these backup systems is comparable to carrying a spare tyre in the car: we do not need it every day, but when we do, it is absolutely crucial. The small extra investment translates into the ability to choose how to live during a blackout: with normality, or in the dark.
What can you do if you already have solar panels?
If you already have a solar installation that disconnected during the blackout, you are still in time to prevent it happening again. There are solutions to upgrade your system and prepare it for future incidents.
Diagnosis: is your current installation compatible with a backup system?
Most solar installations can be adapted to incorporate backup systems, although the process varies depending on the type of inverter and the configuration of your current installation. At Atodosol we offer a free diagnosis where we determine:
- The compatibility of your current inverter with backup systems
- The modifications needed in your electrical panel
- The technical viability of installing batteries if you wish
At Atodosol we always install hybrid inverters, ensuring an easy battery integration in the future.
Steps to upgrade your existing solar system
The upgrade process typically includes:
- Technical assessment of your current installation.
- Backup Box installation and inverter configuration to enable island-mode operation.
- Electrical panel adaptation to separate the critical circuits you want kept powered during a blackout.
- Functional tests to ensure the system reacts correctly to a power cut.
- Optionally, battery storage installation.
Guide for new blackout-proof solar installations
If you are considering installing solar energy for the first time, this is the ideal moment to shield yourself against blackouts from the start.
The essential checklist: what to ask before contracting your solar installation
Before contracting your solar installation, make sure you ask your provider:
- Does the installation include a backup system to operate during blackouts?
- What options do you offer for autonomous operation (backup box, batteries)?
- What percentage of my home consumption can be covered during a blackout?
- What subsidies currently exist for systems with batteries?
- What warranties do you offer for the backup system components?
How to correctly size a system that will never leave you in the dark
The proper sizing of your solar system with backup capacity must consider:
- Critical loads: identify which devices are essential during a blackout (fridge, medical equipment, communication systems, etc.).
- Required power: calculate the total power needed to keep these devices running simultaneously.
- Generation capacity: properly size your solar field considering that, on cloudy days, generation can drop by up to 80%.
- Storage: if you opt for batteries, calculate the autonomy you need (typically between 1 and 3 days).
At Atodosol we run a personalised study of every home to make sure your system is correctly sized to face situations like the one on 28 April.
FAQ on solar systems during blackouts
How long can I keep my home running with a Backup Box?
With a Backup Box, you can keep your home running for as long as there is enough sunlight to generate the energy you need. That means that on a sunny day, you could have electricity from sunrise to sunset. However, when night falls or on very cloudy days, you would need a battery system to keep the supply going.
What appliances can I keep running during a power cut with different solutions?
With Backup Box (no batteries):
- You can use any appliance, as long as the total power does not exceed solar generation at that moment
- As an example, a typical 5 kW system can simultaneously power: fridge, lighting, router/Wi-Fi, TV, computers, device chargers and even the air conditioning if there is enough sun
- Charging electric vehicles is possible at 5 kW, although at reduced power depending on available generation
With a battery system:
- All the appliances mentioned above
- Continuous 24/7 operation, regardless of solar conditions
- More stability for sensitive devices
- The possibility to power the entire house if the system is correctly sized
Conclusion: planning ahead makes the difference
The recent blackout served as a stark reminder of how vulnerable our electrical system is. At Atodosol we have been warning for years about the importance of backup systems, not as a luxury, but as a necessity in a world where energy dependence is growing.
The good news is that the technology to guarantee your energy independence already exists, it is accessible and it represents a fraction of the total cost of your solar installation. Do not wait for the next blackout to take action.
Contact Atodosol today for a free assessment of your current system or to design a new installation that gives you energy peace of mind, no matter what happens with the grid.
Want to know more about how to protect your home during a blackout? Fill out the form below or call us at 692 22 97 13. At Atodosol, your energy is our priority.