Thinking about what happens when prices approach zero makes it hard to make realistic predictions. Yeah infinite power would change everything, but for realistic price shifts there are very different price elasticities for different use cases.
And one person changing their power use doesn't do much to the price, and a large group gradually changing their power use doesn't do much to the price either. So the idea of "If you don't need to use the electricity, someone who is struggling can use it instead." is misguided. The person who's struggling is going to see basically the same price either way. If we want to help them, conserving power won't do the trick outside of specific supply emergencies, we need other measures.
Also roenxi I mentioned things other than lights, but lights happen to be a super clear example of Jevon's paradox not happening over a very significant amount of power usage so of course they'll get brought up.