Step-by-Step Battery Bank Sizing
Getting the right battery bank size is the most important decision in any off-grid power system. Here is how to calculate exactly what you need.
Step 1: Calculate Your Daily Energy Use
List every device you plan to power and multiply its wattage by hours of daily use:
- LED Lights (60W × 6 hrs = 360 Wh)
- Refrigerator (150W × 24 hrs = 3,600 Wh)
- Laptop (65W × 4 hrs = 260 Wh)
- WiFi Router (12W × 24 hrs = 288 Wh)
Total: ~4,500 Wh (4.5 kWh) per day
Step 2: Add a Safety Buffer
Add 20-30% for system inefficiencies (inverter losses, wire losses, cloudy days):
4.5 kWh × 1.25 = 5.6 kWh daily requirement
Step 3: Choose Your Voltage
- 12V system: Best for small setups under 3 kWh
- 24V system: Good for 3-8 kWh systems
- 48V system: Best for 8+ kWh or whole-house backup
Step 4: Calculate Battery Capacity
For a 12V system: 5,600 Wh ÷ 12V = 467 Ah
That means four 12V 100Ah batteries in parallel, or two 12V 280Ah batteries.
Step 5: Plan for Autonomy
How many days of backup do you want without sun? For 2 days of autonomy, double your battery bank. For off-grid cabins, we recommend 2-3 days minimum.
Recommended Configurations
- 5 kWh daily use: 4× 12V 100Ah batteries
- 8 kWh daily use: 2× 12V 280Ah batteries + inverter
- 15+ kWh daily use: 48V system with DL+ 320Ah batteries