Most television sets use between 100 watts and 300 watts of electricity, but the amount of energy a TV consumes depends on three factors: the screen size, the type of technology and the brightness, which can be controlled through the user settings. Today's flat-screen, high-definition televisions, including plasma and liquid crystal display TVs, are generally larger than older, cathode-ray tube sets, and use more energy.
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The cathode-ray tube is the oldest type of TV technology available, dating back to the first commercially available sets in 1939. Bulkier and taking up more space than a flat-panel display, CRT TVs employ inefficient technology: electrons are fired at a phosphor, which lights up the screen to create the image. According to technology writer Michael Bluejay, a 19-inch CRT uses about 80 watts of electricity, with larger screens generally consuming more.
In standard liquid crystal displays, a fluorescent light source -- known as a backlight -- shines light through two polarizing filters sandwiched around either side of a layer of liquid crystal molecules, creating a pattern of light that produces the image on screen. Light-emitting diode LCD sets use the same concept, but the backlight is an LED bulb and can use energy more efficiently. An April 2010 CNET article reports that the average standard LCD uses about 111 watts of electricity; for example, a 46-inch Mitsubishi LCD TV draws about 187 watts, while a 32-inch Vizio LCD consumes about 87 watts. By comparison, a 46-inch Sony LED TV uses about 87 watts.
Plasma TVs demand more power than any other type of television, CNET explains, with the average plasma screen using 301 watts of electricity. With plasma TVs, thousands of tiny, illuminated fluorescent red, green and blue pixels form the picture on the screen. What makes plasmas less energy efficient is that each pixel represents a discrete light source, requiring more power for larger screens with higher resolutions. A 65-inch Panasonic plasma uses about 575 watts of electricity, for example, and a Vizio 42-inch -- about the smallest size plasma screen available -- demands about 283 watts.
Rear-projection TVs rank as the most energy efficient per square inch of screen, but consumer demand has declined thanks to falling prices for less-bulky LCD and plasma sets, according to a November 2008 Consumer Reports article. This type of technology creates a picture, sends it through beams of light to bounce off a mirror, and expands it to full TV screen size. Rear-projecting TVs can use LCD, CRT or digital light processing, which relies on a special chip embedded with microscopic mirrors to create light. Bluejay explains that a 56-inch rear projection TV will use about 175 watts of electricity.