r/Fitness does a weekly "Moronic Monday", a judgment-free thread where people can ask questions that they would ordinarily feel embarrassed for not knowing the answer to. I thought this seemed like a useful thing to have here - after all, the concepts discussed on LessWrong are probably at least a little harder to grasp than those of weightlifting. Plus, I have a few stupid questions of my own, so it doesn't seem unreasonable that other people might as well.
Almost all the available energy on Earth originally came from the Sun; the only other sources I know of are radioactive elements within the Earth and the rotation of the Earth-Moon system.
So even if it's not from the sun's current output, it's probably going to be from the sun's past output.
Hydrogen for fusion is also available on the Earth and didn't come from the Sun. We can't exploit it commercially yet, but that's just an engineering problem. (Yes, if you want to be pedantic, we need primordial deuterium and synthesized tritium, because proton-proton fusion is far beyond our capabilities. However, D-T's ingredients still don't come from the Sun.)