This has been debated to death in the past.
If one looks at the published power consumption figures, one will find that there are LCD's that draw as much or more power than many Plasmas and that the typical power consumption of a Plasma display is much less on average than what the specs indicate, as the specs are sloppy (there is no standard "average power consumption" test criteria, so the manufacturers just put down their own estimate, as it didn't really matter in the past as long as the display didn't exceed the figure they listed).
Power consumption of a PDP is relative to the imagery on the screen--in primarily dark scenes, a PDP can use much less power than an LCD of the same size, as the backlight on most LCD's is on at full brightness all of the time.
In terms of cost, even some of the least efficient Plasma displays would add only a few dollars per month to most people's electric bills-- a cost that could easily be recovered by just swapping out a few heavily used incandescent light bulbs in the house with CCFL's.
It's certainly not fair to single out Plasma displays when all non-projection displays consume more power as the screen increases in size and PDP's, on average, tend to be larger than LCD's.
If they are going to do something like this, they should set a maximum figure for watts-per-diagonal inch, so it will weed out the least efficient displays regardless of size or display technology.
I just don't see how they rationalize making big-screen TV's the target from an energy usage standpoint--on average, the larger a refrigerator I buy, the more energy it uses; the larger a house I buy, the more energy it uses; the faster my computer, the more power it uses; the louder my stereo, the more power it uses; the quicker my hairdryer works, the more power it uses. What's so special about big screen TV's, other than some people can afford them and some can't?