Unfortunately, EnergyStar tests with whatever settings the TV ships with. The EnergyStar test is actually perfectly useless by itself. Perhaps Vizio ships with brightness set very high to show off the rich picture an LED TV is capable of? CNET duplicates the Energy Star tests, but with automatic backlight adjustment set to "off", and they run a second test in Power Saver mode if it's available.
I think this is unlikely. If it were true, then the mfgrs would cherry pick/ship the Feds pre-set TVs to show their product in the best light. My guess is that Energy Star follows a standard testflow that includes initial calibration. I'd hope CNET does the same.
Just like PCs, TV power consumption for similar technology will vary just due to the effort they put into the power supply design. Cheaper TVs, like Vizio, probably did what they needed to do in order to meet the Energy Star and CA requirements and then no more. Some, like Samsung, went well beyond the requirements.
If you really want to delve into the various quirks and flaws of every TV on the market, visit avsforum
. After reading these 100+ page threads per model, you may well lose the will to live.