Hi,
Nothing wrong with your math, but you have assumed a pure sine wave inverter is 100% efficient. They are not. The best seem to be about 88%, but that figure is not under full load. Often (but not always) peak efficiency is at about 60% of full load.
So the 10 amps @ 120 volts becomes 100 amps @ 12 volts.
100 /.88 = 113 amps @ 12 volts. However under a 100 amp load there will be voltage drop. It is often 0.5 volts.
So now the 113 amps is going to be about 4% larger or about 117 amps.
But that doesn't allow for line losses due to resistance.
By the time all those factors are taken into account, dividing the original 1200 watts by 10 is a good ball park for the amps of demand at 12 volts.
avvidclif1 wrote:
Ohms Law.
I = E/P where I = Current, E = Voltage (120), and P = Watts.
A 1200w Microwave would be 120/1200 = 10A
