Shopping for a new TV, a dishwasher, a window? Chances are, most of your options will bear the government's Energy Star logo. So, you may wonder: what does this mark really mean anymore?

The well-known Energy Star logo, carried on a range of products as diverse as light bulbs and doors, has become increasingly common, especially for certain products.

It was featured on 79% of TVs, 75% of dehumidifiers and 67% of dishwashers sold in the United States in 2008, the most recent year for which the government has data, according to a story in today's Washington Post. "That has some observers worried about grade inflation," the paper reports.

In my quest to build a green home, I've noticed real differences in the efficiency scores of Energy Star products. I've spent countless hours on Energy Star's website, one of the government's most helpful, comparing the annual kilowatt hours of refrigerators, dishwashers and clothes washers.

The biggest problem I've had is that some ultra-efficient products are not even Energy Star. This is a problem that the inspector general of the Environmental Protection Agency, which runs Energy Star with the Department of Energy, noted in a report in November.

How could this be?

Some of these products are new and Energy Star has not yet certified them. One example is a General Electric side-by-side refrigerator, introduced in October, that reportedly uses as much energy each year as a 60-watt light bulb.

I've also found this with ceiling fans made by Modern Fan. Its newest models, though using the same motor as its prior Energy Star-rated ones, do not carry the same logo. I called the company to find out why. It says it's submitted the newer ones for Energy Star certification. (Why do I care? My house, when rated by the U.S. Green Building Council, will get points based on the number of Energy Star light fixtures.)

This is not to criticize the Energy Star program, which has tested tens of thousands of products since it began in 1992 and has been a major force in the push for greater efficiency.

Yet consumers, eager to use federal rebates from the "cash for appliances" program that states are gradually rolling out, might want to consult Energy Star's website to select the most efficient products before heading to stores.

Some household appliances, such as refrigerators, are required to carry tags that indicate their kilowatt-hours per year. That makes it easier for shoppers to compare.

In the fall, Energy Star officials said they would update criteria more frequently and thus eliminate lower-performing products from their list. The government updated standards for dishwashers last year and it plans to do the same this year with TVs.

For home appliances, according to the Washington Post, a review will now be triggered when the market share of Energy Star products hits 35%.

Readers: What's your experience with Energy Star products?