Screensavers consume power?

Monitors that are running free screensavers consume the same amount of power as when running normally, which can be anywhere from a few watts for small LCD monitors to several hundred for large plasma displays. Most modern computers can be set to switch the monitor into a lower power mode. A power saving mode for monitors is usually part of the power management options supported in most modern operating systems, though it must also be supported by the computer hardware and monitor itself.

Additionally, using screensavers free with a flat panel or LCD screen instead of powering down the screen can actually reduce the lifetime of the display, since the fluorescent backlight remains lit and ages faster than it would if the screen was turned off completely. As fluorescent tubes age they grow progressively dimmer. A typical LCD screen loses about 50% of its brightness during a normal product lifetime. (In most cases, the tube is an integral part of the LCD and the entire assembly needs to be changed out)

Thus the term "screen saver" is somewhat a misnomer—the best way to save the screen (and also save electricity) would simply be to have the computer turn off the monitor.