Although the industry is promising improvement, at the moment there's little an energy-conscious TV-watcher can do other than physically unplugging the thing - and putting up with a delay when you turn it back on.
The NRDC report estimated that Americans are spending $3 billion a year to power their set-top boxes.
Roughly 80 percent of households in the United States have some form of paid TV, and when you sign up, choices about which box to get are limited.
The report found that the typical configuration of a high-definition set-top box paired with a high-definition digital recorder uses more power than a 21-cubic-foot fridge.
But that wasn't the worst of it. When the researchers went into 50 homes and hooked up energy meters, they found that pressing the "off" button on the remote didn't do much to stem the flow of electrons.
"The aha moment was realizing that hitting the power button does next to nothing," said Noah Horowitz, senior scientist for the New York-based nonprofit. "All it does is dim the clock."
If the box uses 30 watts of power when it's on, it might use 29 watts when it's "off."
The homeowners were horrified, Horowitz said. "Without fail," he related, everyone thought that they were shutting down the power.
Instead, they were adding $25 to $50 to their annual energy bill.
The NRDC scientists estimated that of the $3 billion a year to power all these various boxes, $2 billion was expended when they were supposedly off.
"These set-top boxes seem to be the biggest insomniac in the home," Horowitz said. "They never go to sleep."
He figures it's because there's no incentive for change.
The federal government has devised Energy Star standards for the boxes, and those that meet the standards (listed at www.energystar.gov) are an average of 30 percent more efficient.
