Battery Storage Calculator
Size a battery storage system based on daily energy needs, backup duration, and depth of discharge.
kWh
days
%
USD/kWh
Required Battery Capacity
37.5 kWh
Usable Capacity30.0 kWh
Estimated System Cost18,750 USD
Tesla Powerwalls Equivalent3 units
Required Battery Capacity vs Daily Energy Requirement
How to Size Battery Storage
Battery systems are sized based on energy needs and desired backup duration.
Formula
Usable Capacity = Daily kWh * Backup Days
Total Capacity = Usable / Depth of Discharge
Depth of discharge (DoD) limits how much battery capacity you actually use. Most lithium batteries recommend 80-90% DoD to maximize lifespan.
Example Calculation
A home needing 30 kWh/day with 1 day backup at 80% DoD and $500/kWh battery cost.
- 01Usable capacity: 30 * 1 = 30 kWh
- 02Total capacity: 30 / 0.80 = 37.5 kWh
- 03System cost: 37.5 * $500 = $18,750
- 04Powerwalls needed: ceil(37.5 / 13.5) = 3 units