APC's Go Green Save Green free book tips

[Anonymous user]

There are some tips on the Go Green Save green book that are not very accurate. One of the tips is:

"Choose dark backgrounds for your screen display—bright-colored displays consumer more power."

Most displays sold today are LCD with a TN panel. TN panels acctually wastes 1 to 3 more watt when showing a dark screen compared to a fully white screen. Why is that?

TN screens apply voltage to the pixels commanding them to "close down" so as to block the source of light that by the way is the biggest source of consumption on a LCD display and are always on no matter if you display a white screen or a dark screen. So, when voltage is applied the pixels, they get closed and a dark screen is shown. The opposite happens when a white screen is shown, when voltage is not applied to the pixel, it allows the light to come out and a white screen is shown. I've tested it myself with a wattmeter and that's what happens with a TN panel.

Some more advanced LCD panels, I can't remember now if it is the IPS, PVA or MVA, but one or two of these panel technologies do the opposite of TN Screens when displaying black and white.

All CRTs wastes less energy when darker colors are shown, though.

"Purchase fat-screen monitors—they use signifcantly less energy and are not as hard on your eyes as CRTs."

This is true for the 17", 19", 20" screens. But many people today are going for the 22", 24", 30" and multiple display setups, something that wasn't very common a decade ago. Most people used to have at home a single 15-19" CRTs per computer, people now are buying two, three, four (!) 20" to 30" for using on one computer only!

In my house we still have a 29" Sony Trinitron TV that works very well and it does not waste more than 135Watts as the sticker behind it shows, but I measured it and it acctually wastes 110W. Do you guys know how much power a 32" LCD wastes? The best ones are not below the 200W range! I'm not even mentioning the Plasma screens which can go well above 300W and it's a"flat screen"! At least on this same book APC says:

"Consider a smaller monitor—a 14-inch display uses 40 percent less energy than a 17-inch one."

It doesn't need to be a 14" monitor, a 20" monitor wastes less power than a 14" CRT and if you lower the brigtness and contrast of a LCD screen, which most people don't, you can lower the power consumption to more than 50%, even a 24" screen can waste less power then a 17" CRT or a fully bright 17" LCD, if you lower it's brigtness to 20% or so.

My 20" Samsung LCD wastes about 40W when at 100% brightness. I lowered it to 15% and it nows wastes less than 20W and its light source of will laste longer by doing this.

Message was edited by: rau