Battery Storage Sizing Calculator
Determine the required battery storage capacity for a solar system based on daily usage, autonomy days, and depth of discharge.
Required Battery Capacity
83.3 kWh
Required Battery Capacity vs Daily Energy Usage
Formula
## Sizing Battery Storage for Solar Battery storage bridges the gap between solar generation and energy use, especially overnight or during cloudy days. ### Formula **Required Capacity = (Daily Usage x Autonomy Days) / DoD / Round-Trip Efficiency** Depth of Discharge (DoD) is the fraction of the battery you can actually use without damaging it. Lithium-ion batteries typically allow 80-90% DoD, while lead-acid batteries are limited to 50%.
Exemplo Resolvido
A home uses 30 kWh/day and wants 2 days of autonomy with 80% DoD and 90% efficiency.
- 01Energy needed = 30 x 2 = 60 kWh
- 02Account for efficiency = 60 / 0.90 = 66.7 kWh usable
- 03Account for DoD = 66.7 / 0.80 = 83.3 kWh total capacity
Perguntas Frequentes
What is depth of discharge?
DoD is the percentage of battery capacity you can use. A 10 kWh battery with 80% DoD provides 8 kWh of usable energy. Deeper discharge shortens battery life.
How many days of autonomy do I need?
For grid-tied systems, 1 day is common for backup. Off-grid systems typically need 2-3 days to cover cloudy periods.
Lithium vs lead-acid batteries?
Lithium-ion batteries offer 80-90% DoD, 90-95% efficiency, and 10+ year life. Lead-acid has 50% DoD, 80% efficiency, and 3-5 year life but costs less upfront.