National Public Radio: Power companies are planning to beef up the nation’s electricity transmission grid. At the same time, conservationists are trying to reduce the vast amount of power wasted in Americans’ homes and offices. That raises a question: If we simply used energy more efficiently, would we need to spend billions of dollars on a new grid? To answer this question, we first need to know how much electricity buildings of the future could save. A good place to start is an office in downtown …