Pimptastic wrote:whats the difference in power consumption between CRT and LCD monitors !?
CRT's are extremely inefficient, generating a tremendous amount of heat to do the same function that an LCD does. Some CRT's use over twice as much power as the same sized LCD's.
One other problem with the "power by use" model, as Maugrim hints at, is that computers and monitors generate a substantial amount of byproduct heat. That heat in turn causes an increase in cooling costs - which can be far more substantial than the power used to run the machine.
Regardless, its a relatively minor amount when compared to other appliances (Water heater, Oven, Air conditioner/heater), so power savings by itself probably isn't a significant reason for turning them off. As to the impact on the environment, there are a number of things you can do to improve your energy use, and the computer is probably near the bottom of the list in terms of simplicity, and impact per effort.
Personally, I highly recommend replacing standard lightbulbs with the compact florescent bulbs.. they last longer, are less expensive per year, AND use less energy per year. Then you have the benefits of better insulation, window improvements, weatherstripping, water saving, water heater wrapping, solar heating..
There are dozens of things people can do. Every little bit helps, so definitely, if you aren't using your computer, don't hesitate to turn it off.