ELIZABETH, Colorado — Suddenly, the economics of American suburban life are under assault as skyrocketing energy prices inflate the costs of reaching, heating and cooling homes on the outer edges of metropolitan areas. Just off Singing Hills Road, in one of hundreds of two-story homes dotting a former cattle ranch beyond the southern fringes of Denver, Phil Boyle and his family openly wonder if they will have to move close to town to get some relief. They still revel in the space and quiet that has drawn a steady exodus from U.S. cities toward places like this for more than half a century. Their living room ceiling soars two stories high. A swing-set sways in the breeze in their backyard. Their wrap-around porch looks out over the flat scrub of the high plains to the snow-capped peaks of the Rocky Mountains. But life on the distant fringes of suburbia is beginning to feel untenable. Boyle and his wife must drive nearly an hour to their jobs in the high-tech corridor of southern Denver. With gasoline at more than $4 a gallon, Boyle recently paid $121 to fill his pickup truck with diesel. The price of propane to […]