According to the recently released "2018 International Energy Efficiency Scorecard," a report released every two years by the American Council for an Energy Efficient Economy (ACEEE), which ranks 25 nations (representing 78 percent of all energy consumed on the planet) on 36 energy-efficiency metrics, the five most energy-efficient nations are Germany and Italy (tied for first with 75.5 out of 100 possible points), France (73.5), the United Kingdom (73.0), and Japan (67.0). The average score of all 25 nations is 51 points.

How did the United States fare? In 2014, the nation ranked 13th. By 2016 (when the last survey was released), it had jumped to 8th place, with 61.5 points. This year, however, the U.S. dropped to 10th place, with 55.5 points.

Why the drop? According to the ACEEE, the United States is one of the very few large energy-consuming economies that does not have national energy reduction targets in place. In addition, "The administration's focus on energy production rather than efficiency has meant that progress on federal energy efficiency policies has largely stalled," said Shruti Vaidyanathan, the ACEEE's senior advisor for research.

With regard to the future of U.S. energy-efficiency performance, Vaidyanathan said this trend is likely to continue if the Trump Administration continues to dismantle key regulation.

In addition, the United States' withdrawal from the Paris Agreement suggests that more rollbacks are on the horizon.

"At imminent risk are joint fuel economy and greenhouse gas standards for light-duty vehicles for model years 2021 onwards, a program that put the United States at the forefront of vehicle efficiency efforts," Vaidyanathan said. "The administration's actions could very well affect the U.S.'s future rankings."

On the other hand, the European Union has recently recommitted to energy-efficiency targets.

"We are looking at the polar opposite here in the U.S.," she said.

Still, there are some positive points to note in the United States. Besides aggressive energy-efficiency goals and programs being launched by numerous individual states, the United States as a whole is investing in energy-efficiency programs and research and development, according to the ACEEE, and has tax incentives and loan programs to drive efficiency.