Using a PV system during a power outage: Everything you need to know about emergency power, backup power and storage for your solar system
It's a bright summer's day, your solar system is producing electricity at full speed - and suddenly the screen goes black. Power outage in the neighborhood. You relax and assume that your own PV system will now take over. But to your surprise, everything in the house remains dark.
This is the moment when many system owners become frustrated: A standard solar system does not inherently offer any protection against blackouts.
Why doesn't it actually work? At Verkauf-Bochum, we plan intelligent systems for real self-sufficiency every day. We show you the difference between emergency power and backup power and what really matters when planning - whether for your home, camper or business.
Will my PV system work in the event of a power failure?
No, it switches off immediately for safety reasons. Three core components are essential in order to continue using solar power in the event of a power failure:
- A power storage unit: The battery is the centerpiece. It stabilizes your own home grid if the public grid fails.
- An emergency power-capable inverter: Only a special (hybrid) inverter can set up a stand-alone grid. Make sure it is "black start capable"!
- A transfer switch: This box disconnects your home cleanly and automatically from the public grid in an emergency.
Why does the PV system switch off in the event of a power failure?
If the public power grid fails, the so-called grid and system protection (NA protection according to VDE-AR-N 4105) takes effect for every grid-connected solar system. Your system disconnects from the grid within milliseconds. This shuts down your system for two very good reasons:
- Danger to technicians' lives: when the grid operator patches a line, he assumes that it is without power. If your photovoltaic system were to continue feeding electricity into the public grid, there would be an acute danger to the lives of the workers.
- Protect your devices: When the power from the grid returns, your inverter and the grid are not running synchronously. This clash of asynchronous voltages would destroy your inverter and connected power consumers in your own household.
This means that your PV system switching off in the event of a power failure is not a fault, but a life-saving safety function.
Emergency power and backup power: what's the difference?
If you want to maximize the benefits in the event of a power outage, you have to choose between two completely different concepts: Emergency power vs. backup power. This is where the wheat is often separated from the chaff on the market, as many providers mistakenly lump these terms together.
1. emergency power (the basic emergency power supply)
With a classic emergency power function, the inverter supplies energy via a special emergency power socket or a small, separate circuit.
- How it works: Usually 1-phase.
- What keeps running? You can charge important devices such as the refrigerator, the WLAN router, an LED lamp or your cell phone.
- What does not work? Three-phase large consumers (e.g. electric cars and heat pumps or the electric stove) remain off.
- Conclusion: Perfect for keeping the fridge alive and staying connected.
2. backup power (the real home power backup)
If you want to continue operating the entire house in the event of a power failure, you need a backup power system.
- How it works: The system supplies all three phases in the house. If the power grid fails, the house is automatically disconnected from the public power grid at all poles. The inverter then sets up its own stable stand-alone grid.
- What continues to run? Your entire house. Even large consumers such as heat pumps can continue to run - depending on the power of the inverter and the charge level of the battery.
- Conclusion: The premium solution for maximum self-sufficiency and protection against long blackouts. High-quality systems also have intelligent load management, which switches off unimportant consumers for a short time when the load is high to prevent overloading.
Comparison table: Emergency power vs. backup power at a glance
| Merkmal | Notstromanlage (Basic) | Ersatzstromanlage (Full Backup) |
|---|---|---|
| Hauptzweck | Versorgung weniger, kritischer Verbraucher | Aufrechterhaltung von Betrieb & Komfort im ganzen Gebäude |
| Phasen | Meist 1-phasig | Echte 3-Phasigkeit |
| Versorgungsumfang | Separate Steckdose / kleine Stromkreise | Alle Stromkreise, das komplette Hausnetz |
| Umschaltzeit | Automatisch verzögert oder manuell | Quasi-unterbrechungsfrei (ca. 20 ms) |
| Was läuft weiter? | Kühlschrank, Router, Licht, Handy | Gesamtes Haus inkl. Herd & Wärmepumpen* |
| Netztrennung | Nur die Notstromkreise werden getrennt | Das gesamte Gebäude wird allpolig vom öffentlichen Stromnetz getrennt |
The 3 components to use your solar system in the event of a power failure
"Stable stand-alone operation is no coincidence, but the result of perfectly coordinated hardware. We combine three indispensable components in our system solutions to ensure that your home really does continue to run in the event of a power failure.
- The battery storage system (electricity storage)
The battery storage system is the centerpiece. When the grid is off, the inverter needs a stable voltage source to build up the home grid. In addition, there is no sun at night. Without a sufficiently dimensioned storage system, you're in the dark. The storage system supplies the house when there is not enough sunshine.
2. the hybrid inverter with emergency power capability
A standard inverter is of no use here. You need an intelligent hybrid inverter.
Pro tip: Make absolutely sure that the inverter is black-start capable! This means that if your battery runs out at night in the event of a power cut (which lasts for days), the system switches off. When the sun rises the next morning, a black start-capable inverter can "wake up" the system again without help from the public grid, produce new electricity, charge the battery and supply the house with electricity again.
3. the switchover device (mains switchover box)
To start real stand-alone operation, your home must be physically disconnected from the grid. In most cases, an automatic transfer switch is used, but manual transfer switches are also used less frequently, although they offer less convenience. An automatic transfer switching device does this safely and in compliance with the law within a few seconds.
Watch out for fire hazards: Why expert knowledge is vital for PV storage systems
Here we speak from years of experience at Verkauf-Bochum: The market is currently flooded with cheap components. We see life-threatening constructions time and again - whether in the cellar of a house, on a farm, in a camper or on a boat. If you want to operate a PV system in the event of a power failure, you must not make any compromises. These are the three most common risks:
- Dangerous battery technology: cheap lithium batteries without the necessary certificates or clean communication (BMS) to the inverter are a ticking time bomb. If there is a fire, any insurance cover also expires. We therefore consistently rely on safe cell chemistry (LiFePO4) and certified brands such as Voltsmile.
- Incorrect cabling & undersizing : Cable cross-sections that are too thin lead to extreme heat development with the high currents of an alternative power system. The power of the inverter is also often underestimated: Anyone attempting to start a heat pump with an undersized system risks total technical failure.
- Missing protective devices (earthing): In stand-alone operation, the connection to the public power grid is disconnected. If the system does not automatically establish a correct earth connection, not a single RCD in the house will work. A technical defect thus becomes a deadly danger.
Our philosophy at Verkauf-Bochum
Real security of supply cannot simply be bought "off the shelf". A reliable system is the result of precise system planning. That's why we support you individually with professional circuit diagrams, remote maintenance and technical support during commissioning. In this way, we ensure that your components (such as those from Victron Energy or Voltsmile) work together absolutely reliably and in accordance with standards in the event of an emergency.
Retrofitting a photovoltaic system: How to get an emergency power supply
Do you already have your own PV system and now want to retrofit a backup power supply? This is absolutely feasible. There are basically two technical ways to make your existing system fit for a power failure:
Replace the inverter (the integrated solution)
If your current inverter is already a few years old, a complete replacement is a good option. In this case, you replace the old device with a modern, island-capable hybrid inverter and add a suitable battery storage system.
- Advantage: You have a compact system from a single source that works highly efficiently as there are fewer conversion losses.
Supplementing an AC-coupled system (the flexible solution)
Would you like to leave your existing system untouched? Then AC coupling is ideal. Here, an additional battery inverter (such as the Victron MultiPlus-II) including storage is integrated into your home grid.
- The technical highlight: in the event of a power failure, the battery inverter sets up a local grid. Your old PV inverter "sees" this grid, assumes a functioning public power grid and continues to produce solar power as normal. This means you can achieve full independence even with an older existing system.
Protect your PV system: What does it cost to prepare for a blackout?
The costs depend heavily on whether you are planning a new system or retrofitting one, as well as on the desired capacity in kWh.
- Emergency power solution (basic): A simple socket on the inverter can often be implemented for an additional cost of around 300 to 600 euros (assuming the right inverter and storage system are available).
- Full backup power (domestic grid): For the automatic switchover (switch box) and the intervention in the meter cupboard, you must expect additional costs of approx. 1,500 to 3,000 euros.
- Electricity storage: Depending on the size (e.g. 5 kWh or 10 kWh), modern storage systems cost around 4,000 to 8,000 euros.
The investment not only increases your self-consumption, but also makes you completely independent of the public power grid in the event of a blackout.
Calculation table: What does independence with photovoltaics cost? (estimated values)
| Szenario / Lösung | Benötigte Komponenten | Grobe Preisspanne (Zusatzkosten)* |
|---|---|---|
| Basic Notstrom (Neuplanung) | Hybrid-Wechselrichter mit Notstrom-Steckdose | + 300 € bis 800 € |
| Voller Ersatzstrom (Neuplanung) | Hybrid-Wechselrichter (3-phasig) + Netzumschaltbox + Installation | + 2.000 € bis 3.500 € |
| Notstrom Nachrüsten (Bestandsanlage) | AC-gekoppelter Batterie-Wechselrichter (z. B. Victron) + Batteriespeicher (z. B. 5-10 kWh) + Installation | ca. 5.000 € bis 10.000 € |
| Kompletter Tausch (Bestandsanlage) | Alter Wechselrichter raus → Neuer Hybrid-Wechselrichter + Speicher + Umschaltbox rein | ca. 8.000 € bis 14.000 € |
Solar power checklist: Is backup power or emergency power worthwhile for you?
Being able to fully utilize a PV system during a power outage is a premium feature. Ask yourself:
- Do you live in a region with an unstable grid or frequent outages? (Even if power outages are still rare in Germany, the load on the grid is increasing).
- Do you have to rely on an uninterruptible power supply when working from home?
- Do you have medical equipment or large aquariums that would react fatally in the event of a prolonged outage?
- Is the feeling of absolute security and precaution (blackout protection) worth the extra cost?
If you answer "yes" to one or more of these questions, you should plan your PV system specifically for the power supply in the event of a grid failure. Whether a simple emergency power solution for the most important devices is enough for you or you opt for full backup power for maximum self-sufficiency is ultimately a decision between solid basic protection and maximum convenience.
PV system in the event of a power outage: planned safely with the experts from Verkauf-Bochum.de
A simple solar power system is not enough to ensure that you are not left in the dark and can continue to use your appliances in the event of a power grid failure. You need the magic triangle of a hybrid inverter, a high-quality power storage system and a switch box.
Don't compromise on safety! Avoid cheap do-it-yourself solutions. We at Verkauf-Bochum will be happy to help you plan your personal power plant safely, efficiently and in compliance with standards. Contact us for an individual consultation!
Using the PV system during a power outage: Frequently asked questions (FAQ)
Can I charge my electric car during a power cut?
Yes, but only with a genuine 3-phase backup power system. But remember: an electric car is an "extreme consumer". For the system to remain stable, your PV system must generate a massive surplus at that moment, far in excess of normal household consumption. If the sun is not sufficient, the energy is drawn completely from the storage system - and an electric car can empty a typical home storage system within a very short time. In an emergency, the following therefore applies: first secure the house, then (if at all) charge the car.
What happens if the storage tank is empty during a power failure?
Then you will have no more electricity in the house. It is important here that your inverter is black start capable. Only then will the system start up again automatically at sunrise and continue to supply usable electricity.
Can the backup power overload my home grid?
If all large consumers (stove, hairdryer, heat pump) start up at the same time, this can exceed the output of the inverter - there is a risk of local overloading of the electricity grid in your home. Good systems therefore offer load management and temporarily switch off unimportant circuits in the event of a power failure.
Do I have to register the emergency power function?
Yes. As a backup power system deeply interferes with the electrical system, it must be registered with the grid operator by a certified electrician. This ensures that electricity is never inadvertently fed into the grid while work is being carried out there.