Factors that Affect the Power Consumption of an LCD TV
LCD TV technology consists of a liquid crystal that is polarized by an electric current. Depending on the electric current the crystal either blocks or passes light from a light source (backlight) that is placed behind the liquid crystal layer. (See “How does LCD TV work?" for more details.) The core of the power consumption therefore comes from a) power required to polarize the liquid crystal, and b) the back-light consumption. The size of the screen then determines the main component of power consumption. In simple terms, the larger the size the more power the LCD TV will use. Remember though, the power consumption does not increase linearly with the diagonal screen size. For example, a TV that is twice the size (in diagonal inch terms) will have more than 3 times the power consumption. This is because what matters is the number of square inches that the screen is. Typically, therefore, the power consumption is quoted in terms of per-square-inch. (See the next section for a web-based guide to power consumption.)
The power consumption of an LCD TV naturally depends on the brightness of the picture that is currently on screen. In order to reduce power consumption (and also to increase longevity) a calibration procedure can be carried out. The calibration procedure basically attempts to limit the maximum brightness or luminance of the picture, thereby setting a limit on the peak power consumption of the set. The calibration process is a one-time fix on the peak power consumption of your unit, but the day-to-day power consumption can also be reduced if the brightness of the screen is lowered. If you watch the TV in a bright room, you will definitely have to have the high brightness settings. On the other hand simply drawing the curtains/blinds, or dimming the lighting can help reduce the brightness of the LCD TV screen. Some TVs have light sensors to automatically adjust the picture depending on light conditions. An ISF calibration can also enable you to have presets that adjust the brightness according to the light conditions.
Overall power consumption really boils down to the LCD TV's usage. One important factor often overlooked is that it is more sensible to talk of TV-related power consumption than the TV power consumption alone. Things such as the set-top-box (or DVR), a gaming device, a DVD player, and even the external speaker system that may be attached to the TV all consume power. These need to be taken into account when you look at power consumption in the long run.