New York Times: The biggest opportunity to improve the nation’s energy situation is a major investment program to make homes and businesses more efficient, according to a study released Wednesday by the consulting firm McKinsey. An investment of $520 billion in improvements like sealing ducts and replacing inefficient appliances could produce $1.2 trillion in savings on energy bills through 2020, the study found. The report said such a program, if carried out over the next decade, could cut the …