Actually, it was 1.21 jigawatts, not gigawatts. And you don't really generate that much, if I remember correctly, they used a power surge caused by lightning that ran through power lines. Or something.
Motifake Wit Liberation Front - July 26, 2008, 10:12 am,
A jigawatt is a gigawatt. Back then, not many were as familiar with the prefix giga-, and they ended up pronouncing it as you hear in the film.