Off-Grid Battery Sizing Worksheet

We suggest a battery bank sized to provide enough energy for three days of energy consumption without any charging (solar, hydro, wind, generator) and that will not deplete the battery bank’s capacity by more than 50% and that will compensate for a battery manufacturer’s over-rating of their batteries. 

Follow these steps to determine your battery bank’s size.


Step 1: Determine the watt-hours per day you need (the total from the Off-Grid Load Worksheet) and enter that number on Line 1

Line 1: _____________


Step 2: Multiply Line 1 by 6 and enter on Line 2

Line 2: _____________


Step 3: Divide Line 2 by your system’s nominal voltage (12, 24 or 48) to arrive at a battery bank’s amp-hour rating, which is the typical rating used by manufacturers and enter on Line 3.

Line 3:_____________


Step 4: Multiply line 3 by 1.2 to compensate for what we believe is “over-rating” of capacity by manufacturers. This is the battery bank size you need. Enter on Line 4.

Line 4: _____________