3D TVs use more power when showing 3D content.

There's an interesting article over at CNet, saying that 3D TVs draw more power when showing 3D content. They tested 4 models. The plasma TVs (Panasonic's VT25) used 38% and 50% more power in 3D. Samsung's C8000 LED LCD used 22% more in 3D, and interestingly Sony's HX909 (also a LED LCD) used 1% less power in 3D mode.

The reason is that 3D TVs need to be brighter - because the TV blocks the image half of the time, and also because the glasses block some light (it's like looking at TV through sunglasses).