KANSAS CITY, Mo. — Those yellow labels on appliances that declare how much power they'll use and show you how much you'll save because of their energy efficiency?

They may not be as truthful as you think.

Because of that doubt, the U.S. Department of Energy said earlier this month it's giving appliance makers 30 days to provide more accurate information on their products' energy use. And it promised to take a tougher stance in the future to enforce energy-efficiency standards.

The agency said makers of such products as refrigerators, dishwashers and air conditioners have until Jan. 8 to provide the information, which is primarily used to certify that the products meet minimum energy efficiency standards.

Appliance makers have used the efficiency labels for years in marketing and advertising their products. But the energy department said a review of previous filings for the labels found instances of missing or incorrect information.

After the 30-day information-gathering period, the department said, expedited testing will be started to help determine whether appliances deliver the energy efficiency they're supposed to.

Manufacturers that fall short could be fined.

"We will move forward aggressively in the weeks and months ahead," said Jen Stutsman, a department spokeswoman.

Neither the Association of Home Appliance Manufacturers nor Whirlpool Inc., a major appliance manufacturer, returned calls seeking comment.

The Department of Energy's move comes as the Obama administration pushes energy efficiency and home weatherization, both for the energy savings and as a boost to the economy. A proposed "cash for caulkers" program was announced Dec. 8 and there are already incentives for consumers who buy efficient appliances.

Electric utilities planning for the future are increasingly eyeing energy-sipping air conditioners, heat pumps and other appliances that would reduce demand and limit the number of power plants they'll have to build.

"The thing that keeps coming to the top is energy efficiency," said Michael Chesser, chief executive officer of Great Plains Energy, the parent of Kansas City Power & Light in Kansas City, Mo.

But the interest in energy efficiency has also brought calls for better information about the products. The National Academy of Sciences on Dec. 9 issued a report saying that energy efficiency could reduce energy use by 20 percent by 2020.

But it also said there were obstacles to overcome for that to happen, including a shortage of "trustworthy" information for consumers about energy savings for energy-efficient products.

Lester Lave, chairman of the academy's committee that produced the report, said his son recently purchased an LED lamp whose label claimed that it was 40 times more efficient than a regular lamp bulb and that it would last for 150,000 hours.

"Both of these are false," he said.

Energy efficiency has actually improved dramatically over the years. A new refrigerator supposedly uses about one-third of the energy of one built in 1974.

A separate program, Energy Star, is aimed at selecting the top tier of energy efficient products. In some cases, the information requested by the Department of Energy could be used for those selections, which it has also begun to scrutinize more closely.

The federal agency said it would seek to ban some LG refrigerators from using the Energy Star label because of doubts about the efficiency tests the company was using. LG is challenging the decision.

Reaction to the Energy Department's moves has received support from those who hope they will eliminate confusion and ensure that all products are judged in a similar way.

Consumers Union, publisher of Consumer Reports, has been particularly skeptical of the manufacturers' energy use figures.

Celia Kuperszmid Lehr-man, deputy home editor of the magazine, said the manufacturers have basically certified their own products.

"We welcome the Department of Energy doing more," she said.