I agree that a good test would have to cover a range of modes, but in this one specific instance demo mode is generally the one that will naturally be the bigge

I agree that a good test would have to cover a range of modes, but in this one specific instance demo mode is generally the one that will naturally be the biggest power waster as demo mode for modern TVs virtually always includes "crank the brightness and backlighting to ridiculous, highlight-crushing levels" as one of the settings.