A battery storage system increases the proportion of self-generated and self-consumed solar electricity. In a single-family home, self-consumption rates of up to 90% can be achieved. The actual proportion of self-consumption depends on various factors, such as consumption profile and system size, and can vary widely. Due to their resistance to cycling and constantly falling prices, lithium-ion batteries are the preferred choice today. A photovoltaic system can also be retrofitted with a battery storage system.