TV power consumption

A 50-inch plasma requires a lot of juice.

The price of energy always seems to be rising, and costs can run high when just about every modern appliance can be seen as a power-hungry mass of circuits, lights, and buttons that sucks down electricity, day and night. We put 104 TVs--old and new--to the test by measuring how much power each uses in a simulation of actual use. Our results, detailed in a chart on the next page, show that it can cost between $29 and $223 a year to watch TV, depending primarily on screen size and technology type.

Technology and size matter
There are four basic technologies that TVs use to produce a picture, and technology type has a large influence on power consumption per inch of screen. The traditional cathode-ray tube (CRT) blasts electrons onto chemical phosphors embedded on the inside of the tube, while plasma sets ionize gas to create colors in a million or more tiny pixel cells. SpongeBob or American Idol then show up on the other side of the glass, and both require more electricity to create a brighter image.

On the other hand, flat-panel LCDs and rear-projection microdisplays use a powerful fluorescent backlight or bulb that either punches through an LCD panel with its three color filters or that reflects off of a digital-light-processing chip that has a million miniature mirrors and a spinning color wheel. Either way, they consume the same power, regardless of the brightness of the image. That's because the primary light source--the backlight or the bulb--is essentially always running at maximum power. Note that many flat LCDs actually have adjustable backlights that you can turn down to consume less power and produce a dimmer image.

Size matters as well, so we divided each set's power use by its screen area to get a watts-per-square-inch rating. This way, small and large screens can be compared. While there are plenty of exceptions, the average score of each technology type is telling:

• Microdisplay rear projector: 0.14 watt per square inch
• LCD: 0.29 watt per square inch
• Plasma: 0.35 watt per square inch

If power efficiency is all you're after, the clear choice is rear-projection technology. Of the three, plasma screens are generally the most power hungry. Flat-panel LCDs often have a good brightness-to-consumption ratio, but they're not exactly consistent. Some LCDs are as low as 0.11 watt-per-square-inch, but some go as high as 0.37 watt. Of course, there's always exceptions, the most noteworthy being Sharp's 65-inch LCD that pulled down an amazing 583 watts in use and 76 watts even when it was "off." Luckily, more and more new TVs are coming with a power-saver mode, which we've found can drastically cut power consumption.

In addition to standard power saving modes, which usually just put a cap on a TV's maximum light output, we're seeing a few new power saving measures being used in 2008. One of the most notable is the choice between "home" and "store" use that a TV user will select during initial setup. Choosing "home" engages a default picture mode that saves more power than the standard "torch mode" used as the default setting on most TVs, which is designed for maximum light output to compete against other TVs in a retail store environment. Panasonic's TH-50PZ800U offers this choice, and it makes a tremendous difference in that TVs' power consumption. More radical measures can be found on the Philips 42PFL5603D, which features a variable backlight, a light sensor and an automatic picture adjustment feature. In combination these extras radically reduce power consumption. As power use figures into more TV buyers' decision making processes, we expect to see TV manufacturers implement further measures to help curb their sets' thirst for juice.

Other power factors
It may surprise you to hear that TVs use power even when they're not turned on. So that the TV is ready to respond to the remote in an instant, all sets use what's called phantom or standby power. Our tests revealed that standby power consumption varied widely among different TVs. In most cases, it's just a few watts, but we found several TVs that used more than 10 watts in standby. In any case, it adds up.

Few people have just a TV anymore, and all sorts of ancillary devices contribute to your yearly energy costs as well. Think of all that's plugged into your set, from a DVD player, an A/V receiver, and a gaming console to a satellite receiver, a digital recorder, and even a Wi-Fi transmitter. They all need power. It may not sound like much, but a DirecTV DVR can use about 33 watts, while a Slingbox draws about 9 watts--and these are devices that are typically always on. All told, these boxes can use more power than the TV itself, especially when it comes to gaming. The Xbox 360 pulls down an impressive 187 watts, but is outdone by the power-hungry PlayStation 3, which requires 197 watts of juice.

Unlike with cars and refrigerators, where the law mandates posting of a power estimate, TV shoppers have no way to compare power use. Sure, scanning the manufacturers' specs is a good start, but many don't provide power information, and even those that do often don't use real-world usage specs. Our power consumption chart extrapolates how much it costs to run a TV with given average usage patterns in a real-world scenario.

The chart: HDTV power consumption compared