Inverter Battery Backup Calculator

A 200Ah 12V lead-acid battery with 50% DoD running a 500W load at 90% inverter efficiency will last approximately 2 hours and 10 minutes.

DoD is the percentage of battery capacity that has been discharged. Lead-acid batteries should not exceed 50% DoD, while lithium batteries can safely discharge up to 90%. Discharging beyond the recommended DoD reduces battery lifespan.

Yes. Series wiring increases voltage while keeping capacity the same. Parallel wiring keeps voltage the same but increases capacity. For example, two 12V 200Ah batteries in series = 24V 200Ah, in parallel = 12V 400Ah.

Inverter efficiency is the percentage of DC battery power converted to AC power. Most modern inverters operate at 85-95% efficiency. A 90% efficient inverter loses 10% of energy as heat during conversion.

For a 1000W total load, choose at least a 1250W inverter (25% safety margin). Account for surge power — refrigerators and pumps can draw 2-3x their running wattage at startup. A pure sine wave inverter is recommended for sensitive electronics.

For 5 hours backup at 500W load: Total energy = 500W × 5h = 2500 Wh usable. With 12V lead-acid (50% DoD, 90% efficiency): required capacity = 2500 / (12 × 0.5 × 0.9) = 463 Ah. Use 4 × 200Ah batteries in parallel for 800Ah total.