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. Televisions qualify as a major appliance, and especially big-screen models can make a serious dent in your electricity bill. To find out just how serious, we put 128 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 $30 and more than $100 in electricity per year for the average American to watch TV, depending primarily on screen size, technology type and picture settings.

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 whether they're displaying a dark or a light scene. 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, while some newer LCDs, including ones that use LED backlights, can be set to dynamically adjust the backlight intensity and use less power in dim scenes.

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: 0.13 watt per square inch
• LCD: 0.28 watt per square inch
• Plasma: 0.33 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. Luckily, more and more new TVs are coming with a power-saver mode, which we've found can drastically cut power consumption.

Energy Star 3.0
Partly in recognition of the growing consumer interest in TV power consumption, Energy Star, an international program overseen in this country by the Environmental Protection Agency, has devised a new 3.0 specification for TVs. It improves upon the previous Energy Star specification by actually mandating power consumption standards for TVs while turned on. Amazingly, the previous method only considered standby power (see Other power factors below).

Starting November 1, 2008, HDTVs will have to meet the new specification if they want to bear the Energy Star logo. That specification depends on screen size/area and resolution capability, and is notably technology-agnostic; it doesn't matter whether the TV uses plasma, LCD, rear-projection, or CRT technology. To qualify as Energy Star compliant a 32-inch HDTV must consume less than 121 watts, for example, while a 50-inch HDTV must consume less than 391 watts. Check out Energy Star's pdf of the spec line for more details.

As a result of the new specification, TV manufacturers have already started implementing changes in their 2008 sets. One of the most noticeable is the choice between "home" and "retail" use that a TV user will select during initial setup. Choosing "home" engages a default picture mode, typically labeled "standard," that saves more power than the mode previously used as the default setting on most TVs. Those older default settings, such as "vivid" or "dynamic," were designed for maximum light output to compete against other TVs in a retail store environment. Energy Star testing specifies that if a TV offers the choice between home and retail, testing and qualification must occur in the home mode. Buyers of TVs will usually choose home mode as well, which should lead to less power consumption among new HDTVs.

CNET has recently implemented power consumption testing procedures modeled on those used by Energy Star. The standard is called IEC 62087, and we'll describe it in detail in the How We Test TV Power Consumption section.

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 AV 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.

The chart: HDTV power consumption compared