The 12 countries assessed account for 63 per cent of global energy consumption as well as 62 per cent of the world's carbon dioxide emissions. The United Kingdom topped the list, followed by Germany and Italy. The United States was ranked 9th out of 12, ahead of Brazil (10th), Canada (11th), and Russia (12th).

ACEEE ranked countries using 27 metrics, including: amount of energy consumed relative to gross domestic product, miles-per-gallon ratings for vehicles, energy use per square foot for floor space in residential buildings, and more.

Steven Nadel, executive director of the ACEEE, lauded the UK and the EU for being "well ahead" of North America for its energy efficiency but cautioned that none of the countries received a perfect score in any category. "Unfortunately," said Nadel, "our results show that nowhere is the vast potential for improvements in energy efficiency being completely realized."