To maximize economic efficiency renewables need to supply more than 80% of the country's energy. We can do this with today's technology, and if we did, we'd solve climate change.
What would happen if the power went out for good? It's not a question many of us contemplate, probably because the answer is not reassuring. It turns out that the power grid is quite vulnerable. There are a number of realistic scenarios that could bring it down, not just for a few days, but indefinitely. In addition to that, modern civilization depends on electricity. That is not a figure of speech. We have come to depend on electricity for food and water.