It is tempting to reuse old small LCD computer screens by using two of them on one computer to provide more screen area. But would it be more energy efficient to use one large new screen in place of two old ones?
Older LCD monitors use fluorescent backlights, whereas newer screens use LEDs, which are claimed to be more energy efficient. As an example, the Dell G-Series G2410 24-inch LCD LED backlit screen is rated at 20W, the same as an older 17 inch florescent back-light Dell E1709W.
So using one 24 inch screen would save half the power of two 17 screens. However, how much power do these screens typically use in real operation? If you already have surplus small screens, when does it become better for the environment to replace them with new larger screens?