A primary reason given for the decline, cited in both the NYT article and in more detail by an energy economist from UC Berkley? The large-scale switch to more efficient light bulbs.
The catalyst for the switch was 2007 Congressional legislation mandating efficiency standards for bulbs. When the second phase of that legislation takes effect next year, only compact fluorescent and LED bulbs will meet the standards. LED bulbs use up to 85 percent less electricity than traditional bulbs and can last up to 25 years. And, as with most new technology, the price has come down as it has been more widely accepted.
This is a good example of government-set standards that have spurred a new industry, reduced costs for consumers, and conserved energy, with only minor disruptions.