If you're replacing an old tube TV, and you're wondering about the cost to power a new set, you may be pleasantly surprised. Many of today's TVs won't add more than a couple of dollars to your monthly energy bill. Some can add a lot more, however, so it's wise to look at power consumption as you shop.

Plus, as we make the transition from analog to digital TV, millions of people are buying new sets, most of which are larger than the ones they replace. If most new TV buyers choose energy efficient sets, the cumulative effect on the environment could be big.

Whether you're interested in keeping your energy bill down, or choosing an earth-friendly set, we'll show you how to factor power consumption into your purchase decision. And we'll show you how you can cut the power consumption of any TV just by making a few simple tweaks to the picture controls.

Looking for a label?

If you thought that telling the power hogs from the power sippers would be as simple as reading an EnergyGuide label or looking for an ENERGY STAR logo (like you would when shopping for a refrigerator), think again. It's not that easy, at least not yet.

The original ENERGY STAR rating for TVs looks only at standby power (the amount of power the set consumes when it's turned off), which accounts for a small fraction of the power TVs consume. A new ENERGY STAR rating based on a comprehensive test is scheduled to take effect on November 1, 2008. (We checked in late September and found that a few manufacturers had already released sets that meet the new standard.)

When you compare TVs on Crutchfield.com, you'll see the manufacturer's specs and the Crutchfield test results. Our estimate of monthly power cost is based on 6 hours per day in "power on" mode and a power cost of 10 cents per kilowatt hour.

We do our own testing

Mark, a member of our product research team, with his power consumption test rig.

Back in the summer of 2007, not content to wait for the new ENERGY STAR standard, we asked our Product Research Team to test the power consumption of the TVs we offer. We take the numbers they record and calculate an estimated monthly operating cost for each set. Our formula assumes 6 hours per day of TV watching and 18 hours a day in standby mode. It also assumes that power costs 10 cents per kilowatt hour. Bear in mind that residential power costs vary greatly across the country, from about 8 cents per kWh hour to over 20 cents per kWh. However, even if our formula doesn't precisely match your viewing habits or local power costs, these estimates make it easier to compare power usage between TVs.

Say you're replacing a 36-inch tube TV, which typically costs between $2 and $3 per month to power (at 10 cents per kWh). You'll see as you examine our test results that it's possible to find a new set that won't add much to your monthly power consumption. On the other hand, some of the sets we tested could cost you twice as much.

To save power with any TV, adjust your picture settings

Monster's HDTV calibration DVD can help you get a better picture and save power.

Fortunately, you can cut the power consumption of any TV if you calibrate it or simply reduce the brightness and contrast. This is also a good way to improve your TV's picture for a more detailed, cinematic effect. (TVs come from the factory with their brightness jacked way up, so they'll stand out on a brightly lit showroom floor — but that's probably not what'll look best in your living room.) See our article on TV picture settings for plenty of tips on picture-improving (and potentially power-saving) adjustments.

Testing TV power consumption is easier said than done

The objective is simple: Test the power consumption of TVs in a fair and consistent way that reflects how TVs are used in the real world.

But today's TVs come in several different flavors (LCD, plasma, DLP, etc.), each of which uses a different method to generate a moving picture. Moving pictures present a television with a dynamic signal that varies the set's power demand in step with the variations in color, contrast and motion. A static test pattern would make the test easier, but no one in the real world watches test patterns for fun (we hope).

All of these variables make it difficult to devise a fair and consistent test method. This partly explains why it took the electronics industry and ENERGY STAR authorities a long time to settle on a new standard for power consumption testing.

Before we tackled this challenge, we sought the advice of the experts in the Technology and Standards department of the Consumer Electronics Association. They have been involved in the drafting of the new industry standard, so they were well equipped to assist us.

After conferring with CEA, doing some additional research, and experimenting with a couple of different testing machines, we settled on the test procedures outlined below.

For the sake of consistency, we use the same source component (Denon DVD-1920 DVD player), the same signal path (HDMI, 1080i), and the same video clip for each test. A clip from the Will Smith movie I, Robot was selected for its visual variety. Each TV's picture controls (for color, brightness and contrast) are left at their "factory default" settings.

To make sure that power line fluctuations didn't skew the test results, we plug everything into a PS Audio Power Plant Premier power stabilizer.

To take the measurements, we use a machine recommended by our friends at CEA, the PLM1-LP Single Phase Power Multimeter, manufactured by Electronic Product Design, Inc. It's extraordinarily accurate when measuring standby power, as it's capable of measuring power as low as 0.02 watts.

The first test for each set is a 15-minute test in Power On mode while displaying the clip from I, Robot. Volume is set at 0 for consistency, and because volume settings have little or no effect on power consumption. The power consumption readings are fed to a Dell laptop computer at 2-second intervals, and the results are averaged. Next we test Standby Power for 15 minutes.

Find out more

If you'd like to learn more about electronics and power consumption, and the related impact on the environment, here are two places to start.

• CEA's mygreenelectronics.com site — Along with plentiful info, this site includes an energy use calculator to help you understand how much it costs to power your electronics.
• ENERGY STAR — This site for the government's ENERGY STAR TV standards includes all kinds of useful tidbits.