I always heard that they used less.
Well, I just so happen to have just replaced my old CRT TV. 32", panel 140 watts, with a 46" LCD TV, 256 Watts.
Handy Dandy Kill-a-watt gives an average of 145 watts during operation for the 46" TV, 0 watts 'turned off'
During a test play, the 32" TV gave me an average of 71 watts. 1 watt soft off.
On the other hand,
46" TV: 40"X22.5"=900 Square Inches
32" TV: 25.5X19 = 484.5 In^2
For the screen area, a theoretical 32" LCD TV, scaled perfectly down, would be 78 Watts.
A theoretical 46" widescreen CRT would use 132 Watts.
I'm shocked. My old Sharp CRT uses less juice per square inch of screen, than my energy star rated LCD 46" Sharp. Honestly enough, having bought the old TV 10 years ago I don't remember if it was energy star then, I remember it being a decent TV. I might have the manual still around somewhere, but it's been 3 moves(I kept the box), and I'm not going to go through the bother of searching through a sub-zero garage at the moment. I've been somewhat 'green' for a long time - selecting energy star appliances if available and somewhat sane in price.
Oh, and on the plasma side:
46" Plasma, 628 Watts. Going by the difference in panel ratings(256 vs 628), and 4 hours a day, .20/kwh, the LCD could save you $109/year. From my experience at work, Plasmas DO put out quite a bit more heat than a LCD.
Interesting coincidences keep cropping up: Both are sharps, bought both from the BX, signed up for the AAFES card both times to get extra money off, both times the TV was on special.