Computer Monitors

What Are the Options?

How to Make the Best Choice

The hum of computers, printers, photocopiers and other equipment may be a sign of a busy, prosperous office, but it can also be an indication that some of the company's profits are being eaten up by needless use of energy. Whether you operate one computer or 1000, wasted energy is wasted money. By choosing a monitor with built-in, user-friendly power management features, you can cut monitor energy consumption by as much as 90 percent. Minimizing monitor energy consumption is an important goal, and energy-saving models are readily available.

What Are the Options?

There are two common monitor types available, CRT (cathode-ray tube) and LCD (liquid crystal display). CRT technology used in the typical monitor (and the typical television) consists of a single cathode that shoots electron beams through a vacuum tube, exciting the phosphors, which glow in three colors (red, green, and blue). When these phosphor colors converge, they create the millions of colors available. The monitor's glow is emitted from phosphors in a layer at the front of the screen.

The latest in monitors is the flat-panel LCD, using active- or passive-matrix thin-film transistors (TFT). These are also called FPDs–flat-panel displays (Figure 1). In these monitors, liquid crystals are sandwiched between polarizing filters and charged by transistors. Fluorescent tubes provide the light source, which comes from behind the crystal layer. The voltage level applied by the transistors is what varies the colors and shades and brightness to produce the images. These monitors use less energy than CRT monitors because a "no voltage" or "off" state allows the light to pass through the crystals, such that the white background that makes up most on-screen images draws no energy, except for the fluorescent light source. Full voltage across the crystals creates black, and color uses some state in between.

Figure 1: Flat-panel monitor This 15-inch model is the flat-panel Apple Studio display. Source: Apple

Two key technical features differentiate CRT and LCD monitors: resolution and viewing angle. As LCD manufacturers make improvements to compete with the cheaper CRT monitors, other performance differences that were a problem with older LCD models, such as lower contrast, brightness, and color display, have become less of an issue for general users.

Resolution. Coupled with the computer's graphics card, a CRT monitor can produce a sharp image in more than one resolution. For example, a CRT monitor may be capable of a maximum resolution of 1,280 x 1,024 pixels, but to enlarge the type and images on the screen, the user can change the resolution to 800 x 600 pixels without losing sharpness. An LCD monitor is preset at a maximum native resolution, say 1,280 x 1,024, but when the user switches to 800 x 600 pixels or any other lower resolution, the images are no longer sharp.

Viewing angle. Because the light source on a CRT comes from phosphors on the screen surface, CRTs offer a wide viewing angle of about 160 degrees. Users can clearly see images from almost any position. In an LCD monitor, the effective viewing angle is limited because the light source is behind the screen. Until recently, LCDs offered a 140-degree angle at best. The latest high-end products offer viewing angles of 160 degrees; these products carry a somewhat greater price premium.

Top of Page

How to Make the Best Choice

The bottom line: Flat-panel monitors only offer two solid advantages over CRTs that may attract some niche buyers–slim profile and light weight, and relatively low electricity consumption. (See Table 1 for more comparisons.) However, flat panel monitors are considerably more expensive than CRT monitors, and although prices are coming down, this new technology is not as cost-effective as CRT technology for the time being. For CRT buyers, prices are low, leaving energy management and size as the variables to consider in making an informed purchase decision among the different models available.

Pick a monitor with Energy Star labeling. Monitors that meet Energy Star requirements offer built-in power management capability so you can painlessly save energy. Energy Star-certified monitors automatically power down to 15 watts or less when not in use (see specs in Table 2), consuming up to 90 percent less energy than models without power management features. In the sleep mode, these monitors also emit less heat into the workplace, reducing cooling loads. Both CRT and LCD types are available with Energy Star labeling.

Choose the smallest monitor that will meet your needs. The bigger the CRT monitor, the more energy it uses. For example, a 17-inch monitor consumes 35 percent more electricity than a 14-inch monitor.

LCD and CRT monitors are available in the same sizes, but buyers should be aware that monitor measurements are different between the two types. For example, a 13.5-inch flat-panel monitor has the same size viewing area as a 15-inch CRT monitor. See Table 3 for more comparisons.

Once you've made your choice, you can save even more energy with the following strategies:

• Practice wise power management. Did you know that when your screen-saver is running, the monitor is not "sleeping" but using the same amount of electricity as if you were working away on a spreadsheet or your resume? To save energy while your computer is idle, make sure that your monitor's power-management settings are enabled.
• Turn monitors off at night, on weekends, and anytime they are not being used for extended periods of time.
• Shorten the delay time before your monitor automatically powers-down into sleep mode.
• For older monitors without built-in power management systems, install external control devices that can shut a monitor off after a preset delay.

Top of Page

Copyright © 2006 E Source Companies LLC

Last Modified: January 31, 2007