Light bulbs aren’t sexy, President Obama conceded, as he announced higher efficiency standards for them, but they are important, given that residential and commercial lighting accounts for 7 percent of U.S. energy consumption. Appliances, too, will be facing stiffer standards, along with other household and business products. According to a report on appliance standards issued by the American Council for an Energy-Efficient Economy, the strong new standards for the 26 targeted products could slash U.S. energy use by more than 1,900 terawatt hours by 2030, while reducing carbon dioxide emissions by 7.5 percent over the same time period.

A recent report by McKinsey & Co. also highlighted conservation efforts, suggesting that exploiting as yet unrealized opportunities for improving energy efficiency could reduce U.S. energy use by 23 percent by 2020. The report cited appliance efficiency standards and the Energy Star program as success stories, but identified a number of neglected areas where much more energy savings could be reaped.

A study by the National Research Council is also bullish about greater use of existing energy-efficiency technologies.

Such reports tend to support the view of optimists that a combination of greater conservation efforts and wider deployment of existing renewable, zero-carbon energy sources will be sufficient to meet the mid-century deadline for reducing carbon dioxide emissions to the level needed to avoid a global warming catastrophe.

Others disagree. For example, energy chemist Nate Lewis at the California Institute of Technology has performed a number of calculations that pit the expected growth in energy demand against the energy output capabilities of existing zero-carbon energy sources. He concludes that to meet those targets with such sources by 2050 we would have to build 10,000 nuclear power plants, erect 1 million state-of-the-art wind turbines, and cover 1 million roofs with solar panels every day until 2050.

A recent study by the Brookings Institute seems to support the notion that a huge breakthrough solution is desperately needed. The report suggests that “transformational innovation and commercialization” is necessary and that increased federal spending on R&D along with “bold new research paradigms” are essential to engendering such transformation. In other words, the kind of light bulbs we really need to see are those imaginary ones that appear over the head when someone makes a great discovery and yells “eureka.”

To be sure, there is much promising research under way that could yield such eureka rescues. Many scientists around the world are pursuing photocatalytic water splitting as a means to extract an inexhaustible supply of hydrogen from seawater. Progress continues to be made in bumping up the light conversion efficiency of thin-film solar cells. Researchers at United Technologies Research Center have developed a low-cost system for generating electricity from low-temperature geothermal sources. Babcock & Wilcox Co. has designed a small, modular nuclear reactor that can be manufactured on an assembly line. And ExxonMobil recently announced it plans to invest $600 million to research and develop biofuels produced from algae.

Such efforts should give us hope, but not complacency. Remember that it was a half century ago scientists promised us that unlimited, clean energy from nuclear fusion was only a few decades away. The reality gap on that projection inspired a dark joke: commercial fusion energy is just 30 years away and always will be. “Sun in a Bottle,” a book by Charles Seife, suggests that fusion energy remains an impossible dream.

The laws of physics are impartial, treating optimists and pessimists equally, and it remains to be seen what those laws will allow, and whether that light at the end of the tunnel is a train.

Richard Babyak, Editor E-mail: babyakr@bnpmedia.com