Alternative sources of lights (candles, kerosene lantern and backup batteries who can afford it) are used when there are power outages.

But you're right we do take power for granted but I think what I found most lacking during power outages were not the light source but access to Internet. Just being able to lookup something really quick while you're learning is much more efficient than waiting the next day to ask your teacher to answer it, which is hit/miss sometimes.