NRDC

The Natural Resources Defense Council has ranked the biggest energy hogs in the home, and the thing that's gobbling up the most is probably not what you think: the pairing of your digital video recorder and set-top box.

The environmental monitoring group released a study today that says that a high-definition cable or satellite set-top box when combined with a high-definition DVR uses up 446 kilowatt hours per year. That's more than a new Energy Star rated 21 cubic-foot refrigerator, which uses 415 kWh per year, according to the NRDC's data.

The combination of an HD DVR and an HD cable or satellite box in a house wastes many hours of energy even when not in use, the group found. The study reports that it costs American consumers more in electricity bills per year when they're not using their DVR and set-top box than when they are: $2 billion a year versus $1 billion a year collectively.

The group estimates that there are 160 million set top boxes currently installed in U.S. homes, and together they emit 16 million metric tons of carbon dioxide every year.

Among the different types of set-tops the NRDC tested, streaming only devices (Roku, Apple TV), and standard-definition receivers consumed much less power than HD receivers and HD DVRs.

The problem, the NRDC says, is that many of these set-tops do not have a low-power mode, like a cell phone or a laptop. Hitting the "off" button will typically dim the clock or display, but will not actually turn the device off or even reduce a significant amount of power that it's using in "sleep mode."

"We've improved the efficiency of all sorts of electronics--from TVs to video game consoles," said Noah Horowitz, senior scientist and director of the Center for Energy Efficiency. "It's just as possible to improve the efficiency of our DVRs and other pay TV boxes. But they're not going to build a better mousetrap unless we, the consumers, demand it."

Horowitz suggests consumers can ask their TV service providers that issue set-top boxes, Comcast, DirecTV, Dish Network, Time Warner, and others for Energy Star 4.0-rated devices in order to cut back on electricity use and save money on their monthly bill.