Formula
Current rises when the inverter is less than perfectly efficient:
DC amps = AC watts / (battery volts × efficiency)
The backup page counts batteries for a runtime. This page answers the current one load pulls.
Assumptions
- The load is continuous, not a motor's starting surge.
- Efficiency is a percent you type.
- Battery voltage is the bank voltage, not a single cell unless that is the bank.
Worked example
A 1,500 watt load on a 12 volt bank at 90% efficiency draws 138.89 A.
Input definitions
- AC load
- The watts the inverter must deliver, not the battery watts.
- Battery voltage
- The direct-current voltage of the bank feeding the inverter.
Limitations
This is a planning estimate. The rate, sun hours, and losses are numbers you type. It is not a utility bill, a solar design, or a room-by-room load calculation.
Questions
Does this include surge?
No. A motor can pull several times its running watts for a moment. Size that from the appliance, not from this average.
Is the inverter's rating the same as this current?
The inverter must be rated for the AC watts. This result is the current on the battery cables.