There are approximately 160 million set-top boxes installed in US homes, or the equivalent of one box for every two Americans.
These boxes consume as much electricity each year as that consumed by the entire state of Maryland...
The NRDC study, Reducing the National Energy Consumption of Set-Top Boxes, also found that today's average new cable high-definition digital video recorder (HD-DVR) consumes more electricity annually than the new flat panel TV to which it's typically connected and about 40% more than its basic set-top box counterpart. In contrast, cell phones, which also work on a subscriber basis with a need for secure connections, are able to use extremely low levels of power when not in use – primarily to preserve battery life.Full Report Here