Maintain? We will obviously increase our energy use, and not by a little but by order of billions and billions (non-accurate estimate). We haven't really even started consuming energy yet. We just came out of caves and are barely learning to walk as a civilization.

We don't need to cut our consumption until we actually run out of energy, i.e. have harnessed the whole sun with a Dyson sphere and used up every other source. After that, there are other stars to harness.