They're billed as energy-efficient, but compact fluorescent bulbs are getting a dim review in a new study.

The study, published in Engineering and Technology magazine, shows the energy-efficient light bulbs lose on average 22 percent of their brightness over their lifetime, the BBC reports.

Compact fluorescents reduce energy consumption by up to 80 percent compared to traditional bulbs. But the study concludes consumers were being misled by the bulbs' packaging, suggesting that although the bulbs save energy that savings may come at the cost of long-term brightness.

"It may be deliberate, but because of the standards set, you end up with figures that are exaggerated compared to what people really experience," the magazine's editor, Dickson Ross, told the BBC.

Of the 18 bulbs tested by the magazine for over 10,000 hours, three stopped altogether. Traditional bulbs lose only up to 7 percent of brightness over 2,000 hours.

More on this story from BBC's Web site.