Battery Storage Sizing Calculator

Battery Storage Explained

What is Depth of Discharge?

Depth of discharge (DoD) is the percentage of a battery's total capacity that can be safely used without damaging the battery or significantly reducing its lifespan. Lithium iron phosphate (LFP) batteries tolerate 80–90% DoD, while traditional lead-acid should only be discharged to 50%.

Lithium Iron Phosphate (LFP)

• Higher DoD (80–90%) — more usable energy per kWh
• Longer lifespan: 3,000–6,000+ cycles
• Safer chemistry, no thermal runaway risk
• Higher upfront cost, but lower cost per cycle

Lead Acid

• Lower DoD (50%) — need more capacity for same usable energy
• Shorter lifespan: 300–700 cycles
• Lower upfront cost
• Requires ventilation, regular maintenance

AGM (Absorbed Glass Mat)

• Sealed, maintenance-free version of lead acid
• 60% DoD, 500–1,000 cycles
• Good for RV, off-grid, and backup applications

How Many Backup Days Do You Need?

For grid-tied homes with occasional outages, 1–2 days of backup covers most events. Off-grid or areas with frequent multi-day outages should plan for 3–5 days. Note that you can reduce daily consumption significantly during an outage by avoiding high-draw appliances like electric dryers, ovens, and HVAC.