Home and balcony batteries: when they pay off and how to compare them
Own use with and without a battery, payback, efficiency beyond the data sheet, ageing and safe placement.
What a battery adds
Without a battery, a household typically uses 50 to 70 percent of its balcony solar itself. With a well sized battery this rises to 80 to 90 percent. Because a small system rarely has much surplus, the battery often takes more than ten years to pay for itself. Shifting the washing machine or dishwasher to midday is free and helps too.
Efficiency is not what the data sheet says
In HTW Berlin's 2026 storage inspection the best home battery system was 3.5 times more efficient than the weakest, and the researchers state that data sheet values do not allow a reliable comparison. Look for independent figures such as the System Performance Index and for low standby draw.
How long a battery lasts
Field measurements of German home storage systems over up to eight years found an average loss of two to three percentage points of usable capacity per year, and 2.1 points for LFP systems. Heat is the main driver of ageing: keep the battery out of direct sun and away from hot balconies.