[Symmetry]

I think rather that a 1990s computer would take the full battery (or 180 kJ) to accomplish the same tasks that the macbook air could in 2.5 seconds of operation (~50 J?). So if you changed the task efficiency of the Macbook air to be that of an old computer, but kept the same processing power, the Macbook Air would be consuming 72,000 Watts.