Solar Battery
Calculator
Calculate solar panel and battery requirements for off-grid living. Perfect for van life, RVs, cabins, boats, and emergency backup systems.
No devices added yet. Add a device or load a preset to get started.
Typical: 3-4 (cloudy), 5-6 (average), 7-8 (sunny)
Depth of discharge: 80%
Backup days without sun
Accounts for inverter losses
For grid cost comparison
0 Wh with system losses
0 Wh at 12V (LiFePO4)
Common battery sizes:
Minimum: 0W (25% buffer added)
Example configurations:
Understanding the Calculations
Battery Capacity
Battery capacity is calculated based on your daily energy needs, multiplied by days of autonomy (backup days without sun), and divided by the depth of discharge. LiFePO4 batteries can be discharged deeper (80-90%) than lead-acid (50%) without damage.
Solar Panel Sizing
Solar panels are sized to generate enough power during average sun hours to meet your daily needs and recharge batteries. The 25% buffer accounts for weather variability, panel degradation, and less-than-optimal mounting angles.
System Efficiency
Not all energy makes it from panels to devices. Charge controllers, batteries, and inverters all have efficiency losses. The system efficiency setting (typically 85%) accounts for these losses in the calculations.
Sun Hours
Sun hours vary by location and season. Check pvwatts.nrel.gov for accurate data for your area. Winter months typically have fewer sun hours, so size your system for worst-case scenarios if you're off-grid year-round.