🔋 Battery Size Calculator
Professional energy storage sizing | Global standards (IEC / US NEC) | Auto-update results & graph
Total continuous power consumption of appliances. (USA: typical fridge ~150-800W, worldwide average)
Hours the load runs per day. Essential for daily energy (Wh/day).
Backup days required without recharging. Critical for off-grid & UPS sizing.
Higher voltage = lower current & smaller losses. US NEC recommends 48V for large banks.
Usable battery capacity. Lithium: 80-95%, Lead-Acid: 50% max for longevity (USA best practices).
Cold climates reduce capacity. Factor <1 = cold derating. USA standard (0.8 for extreme cold).
AC/DC conversion losses. High-quality inverters ~90-95% (IEC standard).
Newer years reflect advanced chemistry (LiFePO4, NMC). Reduces required capacity due to higher energy density & efficiency.
⚡ Technology multiplier: 0.95
🔋 TOTAL REQUIRED BATTERY CAPACITY
— kWh
Usable energy after DoD, temperature & efficiency factors
⚡ BATTERY BANK (Ah) @ selected voltage
— Ah
24V system
📊 DAILY ENERGY NEED
— Wh/day
🔧 RECOMMENDED BATTERY STRING
—
➡️ Year factor applied: —
📈 Capacity trend: required kWh for 1–5 autonomy days (current settings)
Based on your Load, Hours, DoD, Efficiency, Temperature & Year multiplier
📘 How to use this tool
- Adjust Load Power (W) and Daily hours → matches your appliance usage.
- Set Autonomy days (how many days you need backup power).
- Choose System Voltage (12V/24V/48V) for your battery bank.
- Modify DoD% depending on battery chemistry (Lithium 80-95%, Lead-acid 50%).
- Temperature & Efficiency sliders reflect real-world losses (cold weather = lower capacity).
- Model Year refines modern battery efficiency (newer = better energy density).
- Calculator updates instantly — results and graph refresh automatically.
💡 Expert tips (field-proven)
- Always oversize by 10-15% for unexpected loads & battery ageing (industry standard).
- In cold regions (below 0°C), increase temperature factor to 0.85–0.9 for lead‑acid.
- For high autonomy (3+ days), lithium batteries reduce weight & allow deeper DoD.
- Use 48V systems above 3kW loads to cut copper losses and increase safety.
- Model year 2025+ batteries: up to 15% higher usable capacity due to advanced BMS & cell tech.
- Calculate using real appliance nameplate values, not estimates, for reliability.