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CNET's power testing goes live in desktop reviews

Our first batch of desktop power efficiency tests are live

Scroll down to the bottom of our last six all-in-one desktop reviews and you'll find CNET Labs' latest addition to the desktop testing regimen. With the help of the Environmental Protection Agency's EnergyStar program, some impressive-looking power meters, and not a little trial and error, we're happy to report that we've finally published the first batch of power consumption results.

Our power results come courtesty of Chroma ATE's EnergyStar-certified 66202 Digital Power Meter. Rich Brown/CNET

We have a few goals in mind with our new power tests. We want to help you make more informed buying decisions, for one thing. You'll see an annual energy cost chart in each review that compares the yearly estimated cost to operate a variety of systems. We don't expect the actual dollar amount will influence most of you one way or another (we're only talking about a range from $15 to $30 in this first round), but an annual cost figure also distills the relative efficiency between systems down to straightforward terms. You can also refer to our newly official Juice Box, located above the cost chart, for the individual power ratings across a variety of usage states for each system.

Apple does exceptionally well on our annual energy cost chart. CNET

Another goal with this testing is to help incent the vendors to take power efficiency seriously. Just like with performance, you can't judge efficiency by the size of a PC, or even the by dimensions of its screen in the case of an all-in-one. We're happy to report that each system we tested falls within the guidelines for EnergyStar's near-official 5.0 specification for computers. Even so, some products, Apple's iMacs in particular, differentiate themselves beyond EnergyStar. We want to be able to highlight those vendors and products that have truly innovated with power efficiency, and also point to those that could improve.

If you're curious about our methodology, you can read about how we power test desktops here. We have a few updates to make to that document, and we also don't spend a lot of time explaining our thinking behind how we test. We've decided to follow the established EnergyStar 5.0 procedures, but with a twist of our own.

Lenovo's IdeaCentre A600 was surprisingly efficient given its large display. CNET

EnergyStar is useful because it provides vendors with an efficiency baseline, but it doesn't yet include a typical computing workload test. Given the many and varied uses for the computers it certifies, the lack of an official EnergyStar load test isn't surprising. Fortunately, CNET has a mostly consumer-focused audience, which gives us a bit more freedom to focus on a specific workload. In addition to the standard round of Off, Sleep, and Idle EnergyStar testing, we've also added a load test that's basically an extended run of our Multimedia Multitasking performance benchmark.

After we compile the test results, we use our own variation of the EnergyStar equation to get the raw annual kilowatt hours (kWh). From there we simply multiply by the national average cost per kWh, currently $0.1135, to come up with our annual energy cost. We gain some efficiency of our own in this process, in that by gathering the requisite EnergyStar test data before adding our own load tests, we can also run just the basic Off, Sleep, and Idle results through the nonmodified EnergyStar formula to gauge whether a system is indeed EnergyStar 5.0 compliant.

You'll find our current power results in each of the following all-in-one PC reviews, as well as in all desktop reviews moving forward:

  • Apple iMac 20-inch
  • Apple iMac 24-inch
  • Dell Studio One 19
  • Lenovo IdeaCentre A600
  • Sony Vaio JS250J
  • Sony Vaio LV250B

You'll also see us add the CNET power rating meter, at left, and currently appearing at the top of more recent TV reviews, to the desktop reviews once we expand our power data pool. We'll be following up with power results on our laptop and monitor reviews shortly. And while our power testing doesn't tell a product's entire environmental story, we hope it will give you a new way to think about choosing your next computer.

Additional reading:
CNET Energy Efficiency Guide