Short answer: Yes, a Balkonkraftwerk mit Speicher can keep essential loads running during a power outage, but only if the system is configured for island (backup) mode or equipped with a hybrid inverter and an automatic transfer switch. Most standard plug‑and‑play units are grid‑tied and will automatically shut down when the utility line is lost—adding the proper hardware and wiring changes turns the installation into a reliable UPS‑style source for a few key circuits.
1. Technical Overview of a Balkonkraftwerk mit Speicher
A typical balcony solar kit consists of one or two 400‑W photovoltaic panels, a small string inverter (often limited to 600 W by the German “Balkonkraftwerk” regulation), and a lithium‑based storage unit that stores surplus energy for later use. Common battery chemistries include LiFePO₄ (safer, longer cycle life) and Li‑ion NMC (higher energy density). Capacities usually range from 512 Wh to 1 024 Wh, which translates to roughly 0.5–1 kWh of usable energy after accounting for an 80 % depth‑of‑discharge (DoD) limit.
For a quick reference, the table below lists three popular models with their key specifications.
| Model | Rated PV Output (W) | Battery Capacity (Wh) | Max Continuous Inverter Output (W) | Estimated Backup Time at 200 W Load (h) | Grid‑Tied Mode |
|---|---|---|---|---|---|
| Eco‑Worth 400‑600 W Kit | 400 | 512 | 600 | ~2.5 | Yes (standard) |
| SunShare Glory‑500 | 500 | 768 | 800 | ~3.8 | Hybrid (optional island) |
| Voltix Pro 800 W Kit | 800 | 1 024 | 1 000 | ~5.1 | Hybrid (full backup mode) |
The numbers above assume an average inverter efficiency of 95 % and a constant 200 W draw (roughly the power needed for a small fridge, a router, and three LED bulbs). Real‑world backup times will vary with temperature, battery age, and actual load fluctuations.
2. Grid‑Tied vs. Island (Backup) Mode
When the public grid is present, a grid‑tied inverter feeds solar power directly into the house wiring and any surplus is stored in the battery. The inverter also continuously monitors grid voltage and frequency. Anti‑islanding protection is required by the VDE‑AR‑N 4105 norm, meaning the inverter will shut down within 0.2 seconds if the grid disappears.
“If you want your balcony solar system to serve as a backup during an outage, you need a hybrid inverter that can switch from grid‑tied to island mode, or add a separate automatic transfer switch (ATS) that isolates the circuits you wish to protect.” – Excerpt from the German Solar Industry Association (Bundesverband Solarwirtschaft) technical guideline, 2023.
Hybrid inverters such as the SunShare Glory‑500 and the Voltix Pro 800 W have a built‑in “backup” mode that disconnects from the utility grid while still converting DC from the panels and battery to AC for the selected load circuits. This requires:
- A double‑pole relay or ATS that can detect grid loss and switch the home circuits to the inverter output within ≤ 30 ms.
- A dedicated backup panel (often a sub‑distribution board) wired to critical appliances such as the refrigerator, router, and lighting.
- Configuration of the inverter’s “grid‑fallback” settings (usually via a smartphone app or a small LCD panel).
3. Backup Performance – Real‑World Numbers
To illustrate how long a typical Balkonkraftwerk mit Speicher can sustain essential devices, consider the following load breakdown:
| Appliance | Typical Power (W) | Hours per Day (Assumed) | Energy per Day (Wh) |
|---|---|---|---|
| LED ceiling light (3 × 5 W) | 15 | 6 | 90 |
| Router & modem | 12 | 24 | 288 |
| Refrigerator (A++ rated) | 80 (average) | 8 (compressor cycles) | 640 |
| Mobile phone charging (5 W) | 5 | 2 | 10 |
| Total | – | – | 1 028 Wh |
If you have a 1 024 Wh battery (like the Voltix Pro model) and keep the above loads,