Calculate how long your inverter battery will last based on your power consumption
Get backup time estimates in seconds with accurate battery efficiency
Plan your power backup system for emergencies and outages
Right-size your battery system to avoid overbuying
This calculator uses industry-standard formulas considering depth of discharge (DoD), inverter efficiency, and battery characteristics for accurate backup time estimates. You can now specify your own DoD value or use the default 70%.
Easily calculate your inverter battery backup time and lifespan based on your power consumption, load requirements, and advanced battery type considerations.
Battery capacity in Ampere Hours
Total power consumption in Watts
Battery voltage (typically 12V, 24V, or 48V)
Enter DoD percentage (10-100%). Default: 70% if left empty
Typical range: 80-90% (default: 85%)
The enhanced Inverter Battery Backup Time Calculator is an essential tool for anyone planning or managing a power backup system. Whether you're setting up a home backup system, sizing a UPS for your office, or planning an off-grid solar installation, this advanced calculator provides accurate estimates of how long your battery system will keep your essential devices running during power outages using industry-standard calculation methods.
Our calculator uses industry-standard formulas that account for real-world factors including depth of discharge limits, inverter efficiency losses, and battery technology characteristics. This provides you with professional-grade accuracy for critical backup power planning, helping you right-size your system and avoid costly over-engineering or dangerous under-sizing.
Input your battery capacity in ampere-hours (Ah), battery voltage (12V, 24V, 48V), and optionally specify your depth of discharge (DoD) percentage for precise calculations.
Enter the total power consumption in watts for all devices you want to run during a power outage.
Click calculate to see your estimated backup time, discharging current, and detailed analysis based on your custom DoD settings.
Depth of Discharge (DoD) is the percentage of a battery's capacity that can be safely used before recharging. It's crucial because deeper discharges (higher DoD) provide longer backup time but significantly reduce battery lifespan. For example, using 90% DoD might give you 2 hours of backup but only 300-500 charge cycles, while 50% DoD gives you 1 hour of backup but 2000+ cycles.
Battery capacity (Ah) measures how much electrical charge a battery can store, while power (Watts) measures how fast energy is consumed. Think of it like a water tank: Ah is the tank size (how much water it holds), while Watts is the flow rate (how fast water flows out). A 100Ah battery can provide 1 amp for 100 hours, but if your device needs 10 amps, it will only last 10 hours.
Choose DoD based on your priorities: Conservative (50-70%): For critical applications where battery longevity matters most. Moderate (70-85%): For regular home backup systems balancing performance and lifespan. Aggressive (85-95%): Only for emergency situations where maximum backup time is essential, accepting shorter battery life.
Inverters convert DC battery power to AC power for your devices, but this conversion isn't 100% efficient. Typical inverter efficiency ranges from 80-90%, meaning 10-20% of battery energy is lost during conversion. A 500W load actually requires 555-625W from your battery (500W ÷ 0.8-0.9 efficiency), significantly affecting backup time calculations.
These calculations provide theoretical estimates based on ideal conditions. Real-world factors like battery age, temperature, actual load variations, and voltage drops can reduce actual backup time by 20-30%. Always add a safety margin and test your system regularly. For critical applications, consult with qualified technicians.
Generally, avoid mixing different battery types (lead-acid with lithium) in the same system due to different charging characteristics and voltage profiles. If you must mix, use batteries with similar specifications and consider separate charging systems. Always consult manufacturer guidelines and consider professional installation for complex setups.
Exceeding recommended DoD can cause permanent damage to batteries. Lead-acid batteries may sulfate (crystal formation) reducing capacity. Lithium batteries may experience thermal runaway or cell damage. This leads to reduced capacity, shorter lifespan, and potential safety hazards. Always stay within manufacturer-recommended DoD limits.
Test your backup system monthly by running a controlled load test. Check battery voltage, capacity, and overall system performance. Monitor for any unusual behavior, voltage drops, or reduced backup times. Keep a log of test results to track battery health over time. Replace batteries when capacity drops below 80% of original rating.
Higher voltage systems are more efficient for larger loads. 12V: Good for small loads (under 1000W), simple setup. 24V: Better for medium loads (1000-3000W), reduced current and wire size. 48V: Best for large loads (3000W+), most efficient, requires fewer parallel connections. Choose based on your power requirements and system complexity.
Add up the wattage of all devices you want to run simultaneously. Check device labels for power consumption, or use a power meter for accurate readings. Don't forget to account for startup surges (2-3x rated power for motors, compressors). Consider running high-power devices separately to reduce total load. Keep a list of essential vs. non-essential loads for emergency prioritization.