When the sun disappears, a balcony‑mounted PV installation without a storage system stops producing electricity. The panels sit idle, the inverter enters standby mode, and every watt you need after dark is drawn from the public grid. In other words, at night your balcony power plant is effectively offline – it can’t feed any energy back and it doesn’t cover any of your consumption.
What the system looks like after sunset
Most balcony kits consist of one or two solar modules (typical 300 – 400 W each) and a small grid‑tie inverter. During daylight the inverter converts the DC output to AC and feeds it into your house wiring. Once the irradiance falls below the inverter’s start‑up threshold (usually around 20 W / m²), the device switches to a low‑power standby state, drawing only a few watts to keep its control electronics alive. The panels themselves generate 0 W because there is no photon energy to capture.
Daily generation profile – a typical sunny day
| Time (h) | Generation (W) | Energy produced (kWh) |
|---|---|---|
| 06:00 – 08:00 | 30 – 150 | 0.1 – 0.3 |
| 08:00 – 12:00 | 250 – 550 | 1.0 – 2.2 |
| 12:00 – 14:00 | 450 – 600 | 0.9 – 1.2 |
| 14:00 – 18:00 | 200 – 450 | 0.8 – 1.8 |
| 18:00 – 20:00 | 0 – 50 | 0 – 0.1 |
| 20:00 – 06:00 | 0 | 0 |
The table shows that a 600 W‑peak balcony system can generate roughly 3 – 5 kWh on a clear day, with almost the entire output concentrated in the 8‑hour window from 08:00 to 16:00. After 20:00 the output is zero, so all night‑time needs are supplied by the grid.
Night‑time load – what’s still running in a typical apartment
| Appliance | Typical power (W) | Night‑time hours (approx.) | Energy used (kWh) |
|---|---|---|---|
| Refrigerator (running ≈ 30 % of the time) | 120 | 8 | 0.32 |
| LED lighting (living room + hallway) | 30 | 4 | 0.12 |
| Television (50‑inch LCD) | 80 | 3 | 0.24 |
| Wi‑Fi router & modem | 12 | 12 | 0.14 |
| Miscellaneous standby (computers, chargers) | 20 | 12 | 0.24 |
| Total night consumption | — | — | ≈ 1.06 kWh |
On average, a single‑person apartment uses about 1 kWh during the 12‑hour night period. A family of two can easily exceed 2 kWh. Since the balcony system produces nothing at this time, the entire amount must be imported from the grid.
Economic consequences – cost of buying night electricity
German household tariffs for night‑time electricity hover around 0.26 – 0.30 € / kWh (including taxes, grid fees and levies). Assuming a nightly import of 1.2 kWh, the direct cost is roughly 0.31 – 0.36 € per night, or about 9 – 11 € per month. Over a year that adds up to 110 – 130 € that cannot be offset by any solar feed‑in because the panels are silent.
During the day you may export surplus to the grid and receive the “Einspeisevergütung” (feed‑in tariff) of around 0.08 € / kWh for micro‑PV systems up to 600 W. That revenue can offset part of the night‑time import cost, but the net effect is still a cash outflow because the price you pay for imported electricity is roughly three times higher than what you earn for exported solar power.
Grid interaction and safety – what the inverter does after dark
According to VDE‑AR‑N 4105, a grid‑tie inverter must stop energising the AC side within 200 ms of a loss‑of‑mains event and must not re‑energise until the mains voltage is stable again. In normal night operation the inverter simply remains in standby, continuously monitoring frequency and voltage. If the grid fails, the device cuts off within its protective window, preventing any back‑feed.
The standby consumption of a typical micro‑inverter ranges from 5 – 10 W. Over an eight‑hour night period that amounts to roughly 0.04 – 0.08 kWh – a negligible cost, but it illustrates that the inverter never truly “switches off”.
Carbon intensity of night electricity – where does the power come from?
The German electricity mix at night is still dominated by a mix of renewables and conventional plants. For the period 22:00‑06:00, the average CO₂ intensity is about 450 g / kWh (based on 2023 Umweltbundesamt data). In contrast, a sunny daytime hour can have a carbon intensity as low as 50 g / kWh when solar generation is high. Therefore, each kilowatt‑hour you draw at night carries roughly nine times more carbon than the same amount generated by your balcony panels during the day. If your goal is to lower your carbon footprint, avoiding night‑time grid reliance is just as important as maximising daytime solar usage.
Practical ways to cut night‑time imports
- Shift high‑power tasks to daylight hours: Run dishwashers, washing machines, or tumble dryers while the sun is still shining. A 2 kWh wash cycle performed at noon instead of