26 June, 2011

From NYT: Set-top boxes - threat or menace?

New York Times of 25 June 2011 had an interesting article about the energy use of the very ubiquitous TV set-top signal converter boxes and DVRs. While I agree with the intent of the article, I think the hyperbole of the lead in paragraph warrants some critical assessment:

"Those little boxes that usher cable signals and digital recording capacity into televisions have become the single largest electricity drain in many American homes, with some typical home entertainment configurations eating more power than a new refrigerator and even some central air-conditioning systems."

Now that might be true for some super-whizzo ground-coupled 25 SEER system attached to an igloo, but it sure seems like magical thinking as I listen to the persistent and determined hum of my compressor at this very moment on a 93 degree afternoon.

Nevertheless, the article does convey some eye-opening, if not eye-popping "facts" that I am prepared to accept relatively uncritically:

  • There are 160 million so-called set-top boxes in the US. 
  • That's about one for every two people, and the number is rising. Many homes have one or more basic cable boxes as well as add-on DVRs, or digital video recorders.
  • The DVRs consume 40 percent more power than the set-top box.
  • A single high-definition DVR and one high-definition cable box use an average of 446 kilowatt hours a year.
  • This is claimed to be about 10 percent more energy than a 21-cubic-foot energy-efficient refrigerator uses.
  • The boxes consumed $3 billion in electricity annually — and two-thirds of that is wasted when no one is watching and shows are not being recorded. 
  • This is more power than the state of Maryland uses over 12 months (I assume the comparison is to the energy used and not to the amount wasted, but either way, certainly non-trivial).

446KWhr annually works out to a steady 24-7 draw of 50.88 watts, a completely believable figure -- at least to me since I have an AT&T Uverse modem (mediates DSL internet access and HD/SD televison), a combined set-top converter and DVR, and a "slave" set-top box for a second (and shamefully still SD) TV. Each set-top device runs a version of MS Windows and takes minutes to reboot.

Bottom line is I tend to agree with just about every assertion in the article. It is unfortunate that the message was diluted by the spurious central A/C claim. If I could cool my home to a tolerable temperature for $10/month, on an annualized basis or not, I'd be pretty thrilled. For the record, making some back of the envelope assumptions, my thinking runs alog these lines:

If my system (compressor, condenser fan, evaporator fan) uses 2000 watts while running (I suspect it is greedier than even that), and runs for 6 hours per day (even in a well insulated 3000 ft^2 home, it probably takes a higher duty cycle than that to maintain a 15 degree temperature difference -- inside versus outside -- and reasonable humidity control) during three months of the year (if only the cooling season were a mere three months!), that comes to about 1100KW-hours right there.

If the US were ever to embrace a no-kidding-around energy independence policy, reduction of the low hanging fruit that these needless parasitic and "vampire" loads represent could play a non-trivial role on the demand side of the equation. Look around your house today. Aside from TV boxes, how many chargers are plugged in for things ranging from cell phones, cordless phones, electric toothbrushes, cordless power tools, etc? How about the ever increasing number of routers and/or wireless access points? It seems untenable to expect folks to unplug them when not in use, so the next step entails incorporating some intelligence into these devices to reduce their standby energy use.

Here's an interesting graphic comparison of some domestic power consumers: http://www.nytimes.com/imagepages/2011/06/26/us/26CABLE-graphic.html?ref=us. I think they screwed up on the duty cycle for the typical home PC however. I expect the great preponderance of PCs to be on 24/7 and thus consume as much electricity as the set-top boxes do and I imagine that a 42 inch plasma TV (probably more common than LCD??) uses more juice. And if we want to get really nitpicky here, one cannot neglect that the waste heat thrown off by all these devices makes the life of your air conditioning system just that much more challenging, right?

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