Balcony PV systems can heat hot‑water using excess solar power

Small rooftop photovoltaic installations – Balkonkraftwerke – in Germany and Austria may generate up to 800 W without requiring registration. A typical two‑person household with a 2 kWp system produces about 1,719 kWh annually, of which roughly 1,031 kWh is fed into the grid without compensation. By adding a 3 kW solar‑powered heating element, up to 972 kWh per year can be redirected to a 120 L hot‑water storage tank, covering about 47 % of the household’s hot‑water demand and cutting grid feed‑in to around 165 kWh. Combining a battery with the heating element can reduce grid feed‑in further to roughly 11 kWh per year. An off‑grid variant uses a DC power‑manager (Sol•Thor) that directly powers the heating element from PV modules, eliminating the inverter and grid connection.