Dive summary:

• The Holy Grail of green building is highly efficient heating, lighting and home appliances, but energy use is up about 2% in post-2000 homes because they're bigger.
• The one area where energy efficiency has outpaced the growth of homes is space heating, where U.S. Energy Information Administration figures show energy consumption is down 21% in 2000-2009 houses from those built earlier.
• Air conditioning is up 56%, however, and lights and other appliances are using 18% more energy in post-2000, larger houses than they used in earlier housing stock.

From the article:

Homes built in the 2000s are 30 % larger on average than older homes—and 17 percent larger than those built just a decade earlier....