Solar Battery Bank Size Calculator
Calculate the required battery bank capacity in Ah and Wh for an off-grid solar system.
Use the Solar Battery Bank Size Calculator
System Parameters
Total watt-hours your loads consume per day.
How many consecutive cloudy days the bank must cover.
50% for lead-acid • 80% for lithium (LiFePO4).
Accounts for inverter, wiring, and charge controller losses. 85% is typical.
Enter your system parameters and click Calculate to see the required battery bank size.
Battery Type Quick Guide
Summary
This calculator determines the minimum battery bank size you need for an off-grid or backup solar system. Enter your daily energy consumption, how many days you want the system to run without sun (autonomy days), your system voltage, depth of discharge, and system efficiency to get the required amp-hour and watt-hour capacity. The result accounts for real-world losses so your bank is sized correctly, not undersized.
How it works
- Enter your total daily energy consumption in watt-hours (Wh/day).
- Set the number of autonomy days — how many sunless days the bank must cover.
- Choose your battery bank voltage (12V, 24V, or 48V).
- Set the depth of discharge (DoD): 50% for lead-acid, 80% for lithium.
- Set the system efficiency (typically 85%) to account for inverter and wiring losses.
- The calculator outputs the required capacity in both Ah and Wh.
Use cases
- Size a battery bank for an off-grid cabin or tiny home.
- Plan backup power storage for a grid-tie solar system.
- Compare lead-acid vs. lithium battery bank requirements.
- Verify an existing battery bank covers your daily loads plus autonomy buffer.
- Design a van or RV solar system with the right Ah rating.
- Calculate how many 100Ah batteries you need by dividing the result.