The Apple TV is a nice addition to any HDTV setup. It's currently the hottest setup component we have next to the PS3. Taken literally, that's because the TV is always on and lacks any form of active cooling, leaving it very warm to the touch. While this is worrying from the perspective of power consumption, it turns out that I should be more worried about the 60 watt incandescent bulb above my head.
According to Apple Support forum-user rverwij, the
Apple TV consumes about 14 watts in standby and between 17 and 19 watts while in use. The reason the Apple TV is always on is probably to increase responsiveness and to sync your content so quickly you don't have to ever manually intervene. Another reason might be to avoid startup times or even to reduce what could be constant wear and tear of booting and shutting down. This
doesn't make it energy-start compliant, though, as rverwij also points out.
To be honest, I wouldn't mind going back in time to defer my purchase of the Apple TV, since clearly the best is yet to come. I also believe that to be the case with the iPhone, which I returned
it unopened a week after purchasing it on release day.
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SOURCE:
Apple Support Discussions
Updated (March 28, 2011): This post applies to the First Generation Apple TV. The newer Apple TV is smaller and more more power efficient than the original and only consumes 6-watts (it only has a 6-watt power supply).