A big part of the solution to the world's energy problems lies in efficiency. On this most people can agree. A shift from incandescent to LED lights cuts direct electricity consumption by 85 percent or more. 7 watts instead of 60 watts. The same amount of light, but less heat so this shift also reduces the need for air conditioning. Insulated walls and ceilings, double/triple glazed windows -- can cut heating and cooling usage by 50%. Fewer big SUVs and more automobiles with hybrid electric or high efficiency diesel engines -- cut gasoline consumption by 20%, 30% or more over 15 years as the auto fleet is replaced.
The U.S. has little to teach the world on these topics, being the biggest consumer of energy by far over the past century. On the flip side, this means that the U.S. will have easier gains from energy efficiency increases than many other countries. Japan ... is somewhere in the middle. It used to be the most miserly developed country in terms of energy consumption, but now my understanding is that much of northern Europe surpasses it in terms of efficiency. So there is plenty of room for efficiency gains.
How much is really possible to save from increased efficiency and conservation? The Washington Post reports on e2e, a new effort at MIT and UC Berkeley that will try to marshall the evidence. The key is to find areas where investments get the most "bang for the buck."
Japan has a number of very successful efforts -- its electric appliances are extremely high efficiency compared with many in the U.S., and shopping for a TV or refrigerator allows one to compare anticipated electricity consumption easily, figures prominently displayed. But Japan sometimes seems weak in the "bang for the buck" choices, pursuing ideas that have the most corporate backing, the most interesting technology, or that have caught a powerful individual or lobby's attention.
One area where Japan has "low hanging fruit" available from conservation and efficiency -- building standards. As I understand it, Japan has none when it comes to energy efficiency. This is one reason why Japanese houses (and smaller apartment buildings) are notoriously cold in winter and hot in summer.
Another suggestion -- when planning new roads, why not implement roundabouts (traffic circles) instead of traffic lights? Europe has done so, to the extent you can travel very long distances on secondary roads without ever stopping at a traffic light. ... whereas in Japan one ends up sitting at what seems like empty intersection after empty intersection.
UPDATE: For a good example of the "low hanging fruit" available in the U.S., which is well behind Japan in the rotation from incandescent to compact flourescent to LED lighting, see this article in the October 6, 2013 CS Monitor. A factory saves more than 90% of its lighting bill (from over $50,000 to under $5,000 a month) by implementing an LED system with a sophisticated monitoring system that provides light in the right amount where and when needed. 2 year full payback on the investment.