It surpsises me how seldom the argument that the universe has always existed comes up, at least in everyday conversations about such matters.
I think this is due to confusing the concepts of the observable universe and the universe in general. People think that because our observable universe had a beginning at the big bang that that is necessarily a creation moment. You don't need the steady state theory to be able to talk about eternal energy (matter is merely a state of energy).
No matter what evidence is produced for the big bang the question of whether energy is eternal is still open. You just have to consider that the laws of physics as we know them don't apply inside a singularity. And human language as we know it might not even be a useful tool in asking the right questions.
For instance, what happened before the big bang? If we accept that the big bang was the moment at which time came into existence then this is not a meaningful question. There can't be a 'time' before time.
Where did the energy come from? Again, without space how do we have 'where'?
We don't know that the energy didn't just leak in from another universe or from whatever state of existence there is outside of our universe (if any).
I think it was Smolin who came up with the idea of universes spawning universes. I think the idea was that black hole singularities are powerful enough to tear through space time and create other universes as their incredibly dense matter spews out.
Despite what the theists will tell you, the question of a cause for the big bang is still open and our science only takes us back to a fraction of second afterthe big bang.