My understanding is that fusion power theoretically has net positive output, but practically no one has achieved this yet. If they are able to achieve such it would be a scientific and commercial breakthrough.
We know that it does, all you have to do is look up at that big ball of fusion in the sky. However, can we humans harness it? We don't know for sure but it sure looks like it. In our lifetimes? who knows, I certainly hope all these new ideas spark some fusion though.
