The capacity of household energy storage batteries should be selected reasonably according to household power demand to avoid waste or insufficient power supply. For small apartments with only daily lighting and small household appliances, 100Ah capacity meets basic emergency power supply. For ordinary three-person families, 200Ah is preferred for photovoltaic energy storage and daily standby power, covering all-day basic power consumption. Large families with high-power electrical appliances and long-term off-grid power demand can choose batteries of 300Ah or above. Reserve 10%-20% capacity margin to meet peak power demand and match battery and inverter load to improve energy storage efficiency.