Where did I get my figures... I made them up. Well, 100W is probably an upper limit on non-DTR laptops (I think mine is closer to 70). Just using round figures to make the calculation simpler.

You can't just multiply AC voltage times AC current to get Watts (though that works for DC). The reason is that you're calculating average power, not peak power, and the voltage times current wave results in a sine^2 power wave. The average of a sine^2 wave is half of its peak, so (using round figures) 100VAC * 20AAC = 2000Wpeak or 1000Wrms.

airbornflight, you're right, I'm not talking about any specific kind of battery. Just the limit on how fast you can store the required energy for a certain period of time, based on device's power consumption and how much power you can get from the wall.

edit-- See my third post in this thread (post#12), I think it's 6 minutes instead of 12, 2000W instead of 1000, due to the fact that the 110V and 20A figures are already RMS instead of amplitude. Thanks airbornflight