BOSTON

FEDERAL FORECASTS predict America’s appetite for electricity will grow in the next two decades by the equivalent of 650 new power plants. If we build all those plants, many of which would burn coal, we can forget about meeting even modest goals for reducing greenhouse-gas emissions and global warming.

Clearly, we will need to build some new power plants, but fortunately, there is another source of energy — not nuclear, solar or wind power — that can help meet our energy needs. It is a “stealth power” that is increasingly finding favor around the country to reduce consumers’ bills, scale back plans for expensive new power plants, and help reduce global warming.

It is energy efficiency, an unglamorous name for an attractive solution drawing the attention of governors, legislatures, investors, businesses and many utilities.

Energy efficiency means using our power more wisely. It means adopting technology we already have so our homes, offices, industries and appliances use less power to do more and waste less. As common-sense as that sounds, it is an enormously muscular tool.

While the federal government lags, states have taken the leadership with creative and aggressive energy-efficiency programs. Those programs have the potential for offsetting all, or nearly all, of the projected energy growth in many regions of the country.

Massachusetts has approved perhaps the boldest energy-efficiency program yet. Part of a landmark energy bill, the law boosts requirements for using renewable energy and mandates that utilities invest in energy efficiency when it is cheaper to do so than buying new power. The law will also use at least 80 percent of the revenue from a regional program to cap power-plant greenhouse-gas emissions for efficiency programs.

Historically, utilities would simply buy more power when demand went up, which would lead to more polluting power plants. Now utilities will have to invest in energy efficiency if it is cheaper to do so than buying new power. The efficiency measures are expected to save Massachusetts consumers hundreds of millions of dollars since the cost of generating stealth energy efficiency is typically a third as much as generating new power.

California is already showing how novel state programs can use the power of energy efficiency. Per-capita electric consumption by Californians now is actually lower than it was three decades ago, in stark contrast to the sharp increase in per-capita electricity use across the rest of the nation. These programs have helped Pacific Gas & Electric avoid having to build dozens of new fossil-fuel power plants in California. And Californians pay among the lowest average electricity bills in America — about 20 percent lower than Massachusetts residents, for example.

States all over America are recognizing the vast potential of energy efficiency. Maryland recently passed a law requiring a 15-percent reduction in energy demand by 2015. Minnesota requires a 1.5-percent reduction each year; Illinois will ramp up to 2 percent a year; Connecticut is on a path to triple its energy-efficiency investments. Sixteen other states have mandatory greenhouse-gas emission reduction goals, most incorporating energy efficiency. Half the states have set up special funds for efficiency programs.

Other states have taken a hard look and are redesigning their utility systems. To spur utility companies to go full-speed on energy efficiency, 10 states have "decoupled" utility profits from electricity sales, the most recent being Massachusetts. The Massachusetts Department of Public Utilities has just issued an order requiring all of the state’s electric and natural-gas companies to revise their distribution rates so that it is now in the utility’s self-interest to help customers lower bills by consuming less energy. California pays utilities to meet efficiency goals, and fines them for failing. Fourteen states have set firm percentages for meeting part of their total energy needs by efficiency.

And states are finding innovative ways to encourage efficiency: offering rebates for energy-saving appliances, providing assistance for homes and businesses seeking to reduce energy use, and financing research on new and better technology.

For these states, the advantages are simple arithmetic. It takes an average of about 3 cents to “save” a kilowatt hour of electricity through energy-efficiency programs. To buy that kilowatt hour costs an average of 8 cents nationally; to build a new power plant to produce it will cost anywhere from 7 to 16 cents per kilowatt hour. And every kilowatt hour not used means another 1 1/2 pounds of carbon dioxide is not released to linger in the atmosphere for centuries.

The U.S. secretary of energy, Samuel Bodman, has called energy efficiency “the cheapest, most abundant, cleanest, most readily available source of energy Americans can access.” Unfortunately, with a few notable exceptions, such as the Energy Star program, the federal government has moved slowly to reap the benefits. States are stepping up to the opportunity, and Massachusetts is now in front of the pack.

Mindy S. Lubber is president of Ceres, a Boston-based coalition of investors and environmental groups working with companies to address sustainability challenges such as global climate change (ceres.org).