How fast do home batteries lose capacity? What eight years of field data show
A 2024 study in Nature Energy followed 21 home batteries for up to eight years. What it found and what it means for the cycle figures on the box.
What the study measured
Researchers led by Jan Figgener monitored 21 home battery systems in Germany in everyday use, some of them for up to eight years. On average the systems lost 2 to 3 percentage points of usable capacity per year. Systems with lithium iron phosphate cells lost about 2.1 points per year.
This is one of the few studies based on real homes rather than laboratory cycling, which is why we use it as our reference. It covers fixed home batteries, not power stations or balcony batteries, so treat it as a guide to the chemistry, not as a test of any product sold today.
Cycles on the box versus years at home
Many units are sold with 3,000 or 6,000 cycles until 70 or 80 percent of capacity remains. At one full cycle per day, 6,000 cycles would take more than 16 years. A battery also ages with time, even when it is barely used. If a loss of about 2 points per year continued in a straight line, a battery would be near 80 percent after ten years, whatever the cycle rating says. The study does not promise a straight line, but it shows that years, not only cycles, set the useful life.
What you can do
Keep the battery in a cool, dry place and away from direct sun, because heat speeds up aging. If the app allows it, avoid leaving a power station at 100 percent for months; many manufacturers recommend storing it partly charged. Check the warranty in years as well as in cycles, and see what capacity the manufacturer guarantees at the end of it. When you compare prices, count with realistic years of use, not with the maximum cycle figure.