From what I've read, the plasmas use 'wayy' more power only if you're displaying an all white screen at full brightness. For normal usage, the diff between LCD and plasma power consumption is not that high.
lcd are more effecient and newers lcds with LED backlight are even more efficent since LCD which have flourscent backlight wastes some energy as heat,where as LCD with LED backlight dont output heat.
if buying something about 50" big, I'd any day buy a PLASMA "eyes closed". none of the LCDs yet c'd produce blacks that i prefer & even the newest generation LCDs have the sick edge bleeding.
I sometimes wonder when people here just run after LCDs without a qualitative analysis. have a look over panasonic plasma's before making a decision, I'm sure they will divert ur mind