How does liquid-crystal display’s computer consume the electricity situation?

How does liquid-crystal display’s computer consume the electricity situation?
How long once electricity?
So long as the size is the same, the different factory brand’s monitor power is nearly same

In which big factory website can you look casually to, for instance LG, above Tristar will have the power

15 inches:about 25W
17/19 inch:about 30W
20 inches:about 40W