With low electricity consumption during the day and high usage at night, how should you choose a solar lithium battery?

Many households encounter a common issue when installing solar systems: electricity consumption is low during the day when the house is empty, but surges in the evening when the whole family returns. How do you choose a lithium battery in this scenario without making a mistake?
The Core Logic: Do the Math on Your Electricity Usage
The key to selecting the right energy storage capacity lies in matching the timing of solar generation with your electricity consumption. You can estimate the required nighttime battery capacity using a simple formula:
Nighttime Electricity Consumption ≈ Daytime Solar Generation − Daytime Self-Consumption
For example: If your solar system generates 17.5 kWh during the day and the household consumes only 5 kWh, you need at least 12.5 kWh of storage capacity for the night. When calculating, you must also factor in system efficiency (approx. 90%) and the battery's depth of discharge (it is advisable to leave a safety margin); therefore, the actual selected capacity should be slightly higher than the theoretical value.
Is a 16kWh Floor-Standing Unit Right for You?
A 16kWh unit is a suitable choice if the following conditions are met:
1. Nighttime household electricity consumption falls within the 10–15 kWh range.
2. There is surplus solar power generated during the day that needs to be stored for nighttime use.
3. There is sufficient installation space to accommodate a floor-standing cabinet.
Why Prioritize Floor-Standing Lithium Iron Phosphate (LFP) Units?
Lithium iron phosphate (LFP) batteries are currently the mainstream choice for residential energy storage due to their high safety, long cycle life (typically over 6,000 cycles), and lower operating temperatures, making them safer for indoor placement. Compared to wall-mounted models, floor-standing units offer easier installation and maintenance, as well as greater mobility, making them ideal for placement in garages, utility rooms, or balcony corners.
When choosing energy storage, the core logic is to calculate based on "actual consumption plus a reasonable margin"—bigger isn't necessarily better, nor is smaller necessarily more economical. Once you calculate your household's nighttime electricity needs, a 16kWh unit will likely prove to be your "golden capacity."