In reply to kipper12:
I have a 26" set, fits in the chimney breast alcove nicely, viewing distance is in the order of 9 or 10 feet (front room, pre-war semi).
This set-up produces howls of derision down at the pub where it seems that, unless an entire wall of your house is covered by pixels, you aren't getting the full benefit.
Accepting that there are different bands of efficiency for TV sets, I still suspect that as a rule of thumb, larger sets use more energy.
Compared to heating and electric ovens ,TV energy use is obviously not in the same league, but then , neither were light bulbs.