单选题 .  Each year millions of Americans with old, inefficient refrigerators in their kitchens buy new, energy-saving ones. That may sound like an efficiency boon (好处，利益), but what's vexing (令人烦恼的) efficiency advocates is that an increasing number of consumers don't actually get rid of the old fridge. Instead, they move it to another area of the house and keeping using it—increasing their energy usage over all.
    America's secondary fridge trend is highlighted in "Energy Vision 2010: Towards a More Energy-Efficient World", a new report by the World Economic Forum and HIS Cambridge Energy Research Associates. The report noted that while the average refrigerator in the United States uses three-quarters less energy than in 1975, despite being 20 percent larger, "the number of U.S. households with two or more refrigerators has increased, and the secondary refrigerators are typically older and less efficient than primary models." Every year about 10 percent of households that purchase new refrigerators keep their old units, a practice that is adding as many as one million secondary units to homes annually.
    Jennifer Thorne Amann, building program director at the American Council for an Energy-Efficient Economy, explained that secondary units are often kept for convenience in larger homes and that owners aren't always aware of how much a "bear and deer" fridge, as they're called in parts of the country where hunting is popular, can cost them. "You are not saving any money on efficiency if you are keeping that old one plugged in," she said.
    Unplugging the 29.6 million secondary units nationwide that are candidates for retirement would save 25 million megawatt (兆瓦特) hours of electricity, or about $2.8 billion, the energy department study noted. Individual owners could save from $420 to $750 in energy costs over the lifetime of an older unit by retiring it, depending on the age of the unit. Some utilities and state agencies have launched programs that offer financial incentives and free pick-up services to entice customers to give up secondary fridges. And some will not issue rebates (折扣) to purchasers of new energy efficient refrigerators unless they provide proof that their old one was recycled.
    "This doesn't mean the efficiency efforts have been in vain or were not worth undertaking," she added, "it means that we should continue improving efficiency and undertake a series of parallel efforts to recycle old units, discourage upsizing and measure the right things if we want to turn absolute consumption downward."6.  According to the passage, the goal to save energy can't be realized because ______.