Battery Sizing Calculator
Calculate the optimal battery bank capacity for your off-grid or backup system based on your daily loads and autonomy requirements.
Properly sizing your battery bank is the single most important step in designing a reliable off-grid or backup solar system. An undersized bank leads to premature battery failure from deep cycling, while oversizing wastes money. This solar battery size calculator uses the industry-standard formula: Required Capacity = (Daily Load x Days of Autonomy) / Depth of Discharge. Enter your appliances below, and the tool calculates the exact kWh and Ah capacity you need for your system voltage.
Works for LiFePO4 lithium, lead-acid, and AGM deep cycle batteries at 12V, 24V, or 48V. Need help estimating your daily loads first? Use our off-grid load calculator to add devices by room.
Daily Loads
System Parameters
Backup duration without solar
Max recommended discharge
Battery bank voltage
Results
Enter your loads and click calculate to see results
How to Use This Calculator
1. List Your Loads
Add each appliance you want to power, with its wattage and daily hours of use. Check appliance labels or use a kill-a-watt meter for accurate readings.
2. Set Autonomy Days
Choose how many days of backup you need without solar charging. 1-2 days is typical for grid-tie backup; 3-5 days for off-grid.
3. Choose Battery Type
Lead acid batteries should only be discharged to 50%. LiFePO4 batteries can safely discharge to 80-90% for more usable capacity.
4. Select System Voltage
48V is standard for most residential systems. 12V and 24V are common for smaller off-grid or RV applications.
Need help sizing your battery bank?
Our team can review your loads and recommend the right solution.