Home storage systems play an important role in the integration of residential photovoltaic systems and have recently experienced strong market growth worldwide. However, standardized methods for quantifying capacity fade during field operation are lacking, and therefore the European batteries regulation demands the development of reliable and transparent state of health estimations. Here we present real-world data from 21 privately operated lithium-ion systems in Germany, based on up to 8 years of high-resolution field measurements. We develop a scalable capacity estimation method based on the operational data and validate it through regular field capacity tests. The results show that systems lose about two to three percentage points of usable capacity per year on average. Our contribution includes the publication of an impactful dataset comprising approximately 106 system years, 14 billion data points and 146 gigabytes, aiming to address the shortage of public datasets in this field.