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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. 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.
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.
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.
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:
What's on the Horizon? LCD monitors are reportedly taking over CRT market share more slowly than expected, probably due to the high prices. As manufacturing methods improve and production quantities increase, look for flat-panel displays to come down in price and gain market share. Meanwhile, prototyping and testing continues on several new display technologies that have the potential to leap-frog past LCDs in the market. These include:
Any of these up-and-comers is likely to be very expensive at first, at least as expensive as LCD panels today, with prices dropping as sales increase. Who Are the Manufacturers? The Energy Star Web site offers a comprehensive table of manufacturers, listing type, brand, model, size, resolution, and watts in sleep mode. Visit the site to view or print this 831-kilobyte table. (Neither this list, nor any mention of a specific vendor or product in this guide, constitutes an endorsement or recommendation of any vendor or product by Platts, nor does this guide constitute an endorsement or recommendation, explicit or otherwise, of your service providers' various technology-related programs.) A nifty commercial computer information site, CNET computers.com, offers product reviews and pricing for a multitude of monitors of all types. You could also try computershopper.com. For more on reducing office equipment energy use, see the following: "Reducing Office Equipment Energy Use," a compilation of online resources by Lawrence Berkeley National Laboratory (LBNL). LBNL's "User Guide to Power Management in PCs and Monitors." The American Council for an Energy-Efficient Economy (ACEEE) "Buyer's Guide to Energy-Efficient Office Equipment."
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