According to Umbra, Energy Star requirements for televisions have gotten more strict and are up to 30 percent more efficient than non-qualified models. To find certified TVs, click here.
Umbra said that when per-inch consumption is measured, the order of efficiency from least to most goes like this: plasma, LCD and rear-projection. Screen size is an important factor when looking at power consumption (so a smaller plasma is comparable to a larger LCD).
In fact, plasma screens are so inefficient that a 42-inch plasma running yearly costs similar to an efficient 25-cubic-foot refrigerator. The EU might even set energy standards for TVS that would effectively ban larger plasma screens altogether. Also, some plasma screens contain lead.
LCDs aren't perfect either, however, as Umbra points out that LCDs contain mercury and their production uses NF3, a potent greenhouse gas.
It's sad to think that there is no television that is 100% environmentally friendly. The best we can do is to think about budget, longetivity and a small energy footprint. Once you find one, remember to use a power strip so you can unplug it when you're not using it. I know that seems like a lot of work, but phantom power is a huge problem. And don't forget to recycle it (which hopefully won't be for a long time!).
To see more tips from Umbra, click here.