American homeowners have come to rely on the DVR to record television programs for them when they're at work, running errands or sleeping. We require our DVRs to work around the clock, so it perhaps should not be surprising to find out that they use a substantial amount of electricity – even more than you might think. Those tiny devices could be preventing many from achieving home energy efficiency.

The National Resources Defense Council determined in 2010 that the electricity required to operate one DVR is 446 kilowatt hours of power annually, which is actually more than a standard 21 cubic-foot refrigerator uses. When the power required to operate all these devices in the United States in 2010 was combined, researchers found the figure to be equal to the electricity used by the entire state of Maryland.

With these figures in mind, some companies have begun creating devices that offer a "deep sleep" feature, where the box is almost entirely turned off, with the exception of a few minor functions that ensure basic functioning. While only two of the 57 boxes that have earned Energy Star certification currently offer consumers this option, that figure should be on the rise in coming years.

"The set-top box is a network device that supplies 100 percent network communications 24/7, but they are power-intensive boxes and shame on us for not paying better attention to that," Joseph Del Rio, from DVR chip production company Broadcom, told Electronic House.

Although many appliances have become much more energy efficient over the years, consumers may not be aware of the existence of these devices unless they perform their own industry research or work with a local D.C. home inspector with knowledge of trends in the green market.