> If I have an inverter that providers 1000W @ 120V from a standard automotive

> 12VDC (13.8VDC) system. Can I calculate the amp draw by doing 1000/120= 8.3A

> to see how much of a drain this device will place on the auto system?

Sorry, no.

The amperage ON THE 120 V SIDE will indeed be 8.3 A, if the load is

resistive. But you wanted to know the current on the 12 V side. The

inverter acts like a transformer. Voltage transforms one way; current

transforms the other way.

1000W out means something greater (in watts) into the inverter. For

purposes of this exercise, let's say the inverter is 90% efficient at

this power level, meaning it draws 1111 watts from the 12V side. The

excess 111 watts goes into heating the inverter.

1111 W / 13.8 V = 80.5 Amps, drawn from the car's electrical system.

If the DC voltage drops, say to 12.0 V, then the current increases to

92.6 A to deliver the same power.

If the inverter's efficiency is less than 90%, the required input

wattage, and amperage, must be greater.

Regards,

Andy