Leaving your Xbox One or PlayStation 4 in standby mode could waste more energy than you think, according to the Natural Resources Defense Council. The nonprofit agency found that both consoles utilized at least twice as much energy per year as their predecessors the Xbox 360 and the PlayStation 3.

The New York City-based nonprofit environmental advocacy group also revealed that Nintendo’s Wii U was an “energy sipper.”

“We don't have a problem with people playing games. But the problem is the amount of energy used when not playing a game," Pierre Delforge, the council’s director of high-tech energy efficiency, told USA Today last week.

Delforge claimed that even in standby mode, Microsoft’s Xbox One used 15 watts of continuous power so it can immediately respond to voice commands. The PS4 used 8 watts so its controllers can be charged. The average desktop computer used less than 2 watts in sleep mode.

"This adds up to several power plants of electricity," Delforge added. He also noted the average lifetime energy cost of owning an Xbox One is $150, which is five times higher than the Wii U.

The NRDC discovered that the new consoles use more energy when playing videos or in standby mode than when playing games. It also said the PS4 and Xbox One use 30 to 45 times more power to stream a movie than media players like Amazon Fire TV or Apple TV.

The PlayStation 4 and Xbox One launched last November. Both devices sold more than 1 million units within 24 hours of their releases, but the PlayStation 4 currently seems to be leading in sales, with 7 million consoles sold as of last month.

Though Delforge believes consoles have made positive progress in energy efficiency since the council’s previous report in 2008, he feels that newer features like voice command or television capabilities have somewhat hindered this progress.

To save energy, the NRDC suggests setting your consoles to auto-power down when not being used. You can also disable automatic and other connected standby modes.