How Much of a Power Hog is Your Flat Screen TV?
By Alfred Poor, dealnews contributor
Ten years ago, the average television Americans bought was a 30" CRT (picture tube). One of these sets drew about 115 watts when on, which is nearly as much power as a pair of standard 60 watt incandescent household light bulbs.
These days, we're buying flat-panel LCD and plasma televisions, some of which are many times larger than that 30" CRT set. Are these power-hungry monsters the reason our electricity bills are going through the roof?
Let There Be Light
Plasma uses electricity to excite a gas so that it emits invisible ultraviolet light. This then strikes chemical phosphors that emit light. The light is red, green or blue, depending on the chemical composition of the phosphors. (This is essentially the same process that goes on inside fluorescent lamps, except that their phosphors emit white light.) If you're showing a bright image on a plasma screen, it is using close to its maximum energy consumption. If the image is dark with lots of shadows — think Marlon Brando's scenes in "Apocalypse Now" — then it does not need to create as much light, and it uses less power.
On the other hand, LCD panels don't make any light. They need a bright light shining from behind so that you can see the image. In general, the power consumption is the same no matter what the image is. (Some sets use "local dimming" to save energy, which we'll get to in a minute.) So unlike plasma, LCDs consume a constant amount of power while they are on.
Both plasma and LCD panel technology has been improving in recent years, and one area of improvement has been energy efficiency. For example, plasma panels have been engineered to contain more phosphors, which means more light can be emitted from a plasma discharge.
LCDs have made improvements in efficiency through the use of better light management layers. One of the biggest changes, however, has been to change from a cold-cathode fluorescent lamp (CCFL) to light emitting diodes (LED) for their backlights.
In addition to eliminating the mercury used in CCFLs (which is toxic and a hazardous waste), LED backlights also use less power making them the most energy-efficient TVs. For example, here is a comparison of the power consumption ratings for some different LCD HDTV models:
- The Sony EX520 Series uses LED backlights, and the EX420 Series uses CCFLs. For the 46-inch model of both lines, the LED model is 1.65" thick (more than 2" less than the CCFL model), and rated at 103 watts compared with 117 watts for the CCFL model. That's a 12% power savings. (Note also that this is a much bigger screen than the 30" CRT mentioned in the beginning, yet it draws less power.)
- You can find an even bigger difference when comparing some Samsung models. The 46C630 is a CCFL model, and the 46D6000 model uses LEDs. The LED version is 1.2" thick, which again is more than 2" less than the CCFL model. For power consumption, the CCFL unit is rated at 104 watts, but the LED model is rated at just 67 watts, or a 36% savings. That's also just slightly more than half the 30" CRT rating, even though it is a 46" HDTV.
Look for the Energy Star
The Environmental Protection Agency (EPA) has had Energy Star ratings for electrical appliances, including televisions, for many years. The ratings for televisions are now up to version 4.0 which took effect in May 2010. These ratings are about 40% lower than the previous version. You can find a list of the televisions that meet these requirements at the EPA Energy Star site. The requirements adopted by the California Energy Commission are similar to the Energy Star 4.0 levels, which televisions must meet in order to be sold in California.
In September of this year, however, version 5.3 ratings go into effect. These cut consumption limits by about 30% more than the current ratings, and no longer prorate the requirements for screens larger than 50".
These new requirements are going to be very difficult to meet for plasma and CCFL LCD displays. As a result, you will likely see even more LED backlight LCD HDTVs on the market.
LEDs can meet these more stringent requirements for a number of reasons. One is that they are a more efficient light source than fluorescent. In addition, it is easier to dim the backlight in response to the image content. Some sets can only dim the entire backlight, which others can selectively dim horizontal or vertical stripes, or even smaller regions in some cases. This helps reduce power consumption, as well as increase the apparent contrast of the display.
The bottom line is that the television you buy today uses just a fraction of the power used by the television you bought 10 years ago, but that still isn't going to be good enough to meet the latest standards in some cases.
Choosing an energy efficient set will soon be easier, as the Federal Trade Commission now requires a new Energy Guide label for all televisions manufactured after May 10, 2011. This new sign shows the average cost to run the set for a year. For instance, the cost to run the new Vizio 32" E320VP is rated at just $8 a year. It consumes only 37 watts on average, which is a 68% reduction from that average 30" CRT model.
With that kind of news, you will be able to sit back and enjoy your new HDTV without worrying it will run up your electric bill.