These measurements are according to a handy plug in power meter I bought around 5 years ago. When on, LCDs use around 30 watts. CRTs are much more variable, ranging from 50 watts to 120 watts and averaging somewhere around 80 watts. You'll see as much as 50 watts more energy for a CRT to display an all white image versus all black. Bumping up the resolution (like, from 1024x768 to 1200x1024) takes another 3 to 10 watts for each step up, and finally maximum contrast and brightness settings can up the power usage 10% over having contrast and brightness set to the halfway point. I saw similar power usage in a typical CRT based 19" TV. All that barely matters with an LCD.
Interesting that WYSIWIG had this hidden cost. I never cared for the black text on the white background, and always tried to have it the other way around. With the white background, felt like the monitor was trying to irradiate me.
On the 19" ones I have they almost the same in CRT vs LCD but it depends as you said on what is on the screen. With a black screen the LCD used about 10 more watts, on a white screen the CRT used about 20 more watts.
I wonder how plasma falls in this mix?
I also think it depends on the set, my 19" CRT is an energy star and I know it uses about 1/2 what my old 19" CRT did so that helps for sure.
Free CRTs rescued from the dumpster were what I had used for years until the recycling mandate went into effect and really cut my ability to upgrade to bigger/better. The LCD / TFT flat panels came down in price enough that I broke down and bought one, new even. The energy savings will probably never match the free cost of the CRTs, but the restoration of literally square feet to my desk work area alone is well worth the price of admission.
I think the 19" monitor (Energy Star rated also) that I can run up to 1600x1200 draws about 180 watts where the 26 inch LCD HDTV draws 55 watts on the lowest power setting. It only does 1330x768 however but it is a lot larger and easier to read from a distance. I also use a laptop instead of a desktop and the entire laptop uses 30 watts operating a 12" diagonal screen.
Yup, my 19 inch CRT at 1024x768 pulls between 65w and 80w, I haven't bumped the res up more then that but have the contract pretty high and the brightness about in the middle. The 19" LCD uses 70w no matter what.