When it comes to power generated, or fuel produced, being consumed, I want to know that it isn't being wasted by inefficient technology. A good example of the benefits there: The power grid infrastructure did not need to be increased as population increased due to increased efficiencies in appliances, lighting, etc... Demand actually decreased.
When it comes to sustainability, true sustainability and not just some corpo-babble buzzwords, there is an emotional aspect of it. I look at the things that we as a planet have lost, or are ignorantly losing. I'm not going to expand on that - you think about it.