Load Current (Amperes) Enter the total current drawn by your devices (e.g., 5.5)

Backup Time (Hours) Enter how many hours you need the backup to last (e.g., 3.5)

Efficiency Factor (0–1) Enter system efficiency (e.g., 0.85 for 85%). Leave blank for 100%.

Quick Examples:

Small Inverter Solar Storage

Calculate Clear

This calculator is for informational purposes only. Verify results with appropriate professionals for important decisions.

What Is Battery Capacity

Battery Capacity measures how much energy a battery holds. It tells you how much current a battery can provide for one hour. Think of it like the size of a fuel tank. A bigger number means the battery can run your devices for a longer time before it needs to be charged again.

How Battery Capacity Is Calculated

Formula

First, we multiply the current by the time to find the total charge needed. Then, we divide by efficiency because no system is perfect; some energy is lost as heat. This gives the actual battery size you need to run your load safely for the set time.

Why Battery Capacity Matters

Knowing the right battery size prevents your devices from turning off too soon. It helps you save money by not buying a battery that is too big or too small for your needs.

Why Correct Sizing Is Important for Device Safety

If the battery is too small, it may run out of power quickly or get damaged from being empty too often. If it is too big, it costs more money than needed. Proper sizing ensures your devices run safely and efficiently during a power outage.

For Home Inverters

For home use, this calculation helps you choose a battery that can run fans and lights through the night. It ensures you have enough power stored to last until the electricity comes back on.

For Solar Systems

For solar setups, you need to store sun energy for the night. This calculation helps you size the battery bank so you do not waste extra solar power but have enough for cloudy days.