Selling Excess Energy Back to the Grid – The Basics
Short answer: yes, a Balkonkraftwerk mit Speicher can push surplus electricity into the grid, but only when the system meets specific technical, legal, and contractual requirements set by the German energy regulator and your local distribution network operator (DNV). In most German states, a 2‑3 kW PV unit equipped with a small lithium‑iron‑phosphate (LiFePO₄) battery qualifies for feed‑in tariffs under the EEG (Erneuerbare‑Energien‑Gesetz) as long as the inverter is certified for anti‑islanding and a bidirectional meter is installed.
Legal and Regulatory Framework
Germany’s EEG 2023 (as amended in 2024) distinguishes between self‑consumption and feed‑in for small PV installations. Installations up to 10 kW are eligible for a fixed feed‑in tariff (Vergütung) that is paid for every kilowatt‑hour exported. The exact rate varies by year and is indexed to the consumer price index. As of 2024:
| System Size | Feed‑in Tariff (ct/kWh) | Self‑Consumption Tariff (ct/kWh) |
|---|---|---|
| ≤ 2 kW | 8.20 | 12.40 |
| 2 – 5 kW | 7.90 | 11.90 |
| 5 – 10 kW | 7.60 | 11.50 |
To qualify, the plant must be registered in the Marktstammdatenregister (MaStR) and the installer must provide a certificate of conformity for the inverter (VDE‑AR‑N 4105). The distribution operator may also demand a smart meter gateway for systems larger than 6 kW, which adds a monthly fee of roughly €3–€5.
Technical Prerequisites for Export
Even if the legal conditions are satisfied, the physical export of electricity requires a set of hardware and configuration standards:
- Bidirectional meter – capable of recording both import and export flows. Traditional Ferraris meters are not allowed for feed‑in.
- Anti‑islanding inverter – must comply with EN 50438 or the newer VDE‑AR‑N 4105, ensuring the inverter shuts down within 0.2 seconds when the grid is lost.
- Smart Meter Gateway (SMGW) – mandatory for installations > 6 kW; it provides encrypted data transmission to the DNO and the energy supplier.
- Proper grounding and protection – a residual‑current circuit breaker (RCCB) type A (30 mA) must be installed on the AC side.
For a typical 2.5 kW Balkonkraftwerk, the inverter’s rated output is usually 2.5 kVA, which matches the PV panel’s DC rating. The system’s maximum export current is limited to 16 A per phase, complying with the German low‑voltage regulation.
Storage Integration: How Batteries Change the Equation
Adding a battery introduces a decision layer: should excess generation be stored first for later self‑use, or can it be exported immediately? The answer depends on the round‑trip efficiency and the control strategy of the inverter.
| Battery Chemistry | Round‑Trip Efficiency | Depth‑of‑Discharge (DoD) | Typical Life Cycle (80% DoD) |
|---|---|---|---|
| LiFePO₄ (LFP) | 95 % | 90 % | ≥ 4,000 cycles |
| Nickel‑Manganese‑C
|