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August 11, 2009 / Jim Fenton

Power Switches that Aren’t

No-opA few weeks ago, I noticed a colleague at work had a Kill-A-Watt power usage meter, which he allowed me to borrow.  It’s a great device, and relatively inexpensive, so I quickly bought one for myself.

I went around the house measuring all sorts of devices, particularly things like my networking gear that is on all of the time, some of the computers, and entertainment equipment.  As expected, many of these devices draw some power in their standby modes; this is necessary if they have a clock, or can be turned on via a wireless remote.

I was expecting the DVR (DirecTV HD model) to take a significant amount of power on standby, but I was shocked by the comparison between “off” and “on” power usage:

On: 40 watts
Off: 38 watts

That’s right, there is only a 2 watt difference between being turned on and turned off!  It seems that all that the “power” button must do is to turn on the front-panel LEDs and turn on the video output circuitry.  Of course, there are a lot of nice features you get by having the receiver effectively on all the time:  the program guide is continuously up to date and the remote recording feature allows one to request a recording via the Web or an iPhone app.

So I checked our bedroom set, which is connected to an older-model, non-HD, DirecTV receiver:

On:  11 watts
Off: 10 watts

Only 1 watt different!  The program guide still needs updating for this receiver, but of course one can’t remotely request a recording from it.

Does it have to be that way? I’d be happy with a program guide that’s a few hours old, and with remote recording that requires that I give it a little bit of advance notice.  So why not have the receiver (and recording processor and disk in the DVR) switch to a “real” standby mode most of the time, with a timer that wakes it every so often to receive instructions and updates from the satellite?  It would also wake when a remote-control or front-panel command is received.

How much power are we talking about? At the end of 2008, DirecTV had 17.6 million subscribers.  Let’s assume (I think very conservatively) that there are 10 million DVRs and 10 million non-DVRs (since some subscribers have more than one TV).  Suppose, through power cycle management, we can reduce power consumption 90% of the time to 2 watts for the non-DVRs (typical of home audio equipment) and to 10 watts tor the DVRs (typical of a sleeping home computer).  That works out to a savings of 324 megawatts, just for DirecTV customers.  Other satellite receivers, DVRs, and cable set-top boxes have this problem as well, although I don’t know to what extent.

Another way to look at this is that a more efficient DVR could save about 221 kWh per year, and a more efficient non-DVR receiver could save about 65 kWh/year.

The irony is that on both receivers, the button is labeled “Power”.  It’s almost as if they felt they needed that button as a feel-good measure.


Leave a Comment
  1. rgh / Aug 12 2009 3:31 pm

    As expected, many of these devices draw some power in their standby modes; this is necessary if they have a clock, or can be turned on via a wireless remote.

    While this is true in an absolute sense the amount of power they actually need to draw is miniscule. It’s purely lazy design on most counts. To enable a remote to turn on a device, correctly done, means said device should draw milli Watts. Devices containing computers can periodically woken up to download listings etc, again the average power consumption can be reduced to a very small amount without affecting functionality.

    But low power design is not easy so they skimp; the circuitry to periodically wake a device up costs money so they leave it out.

    If companies where charged for the power consumption that the device consumes over it’s entire lifetime we would see a dramatic reduction in the stand-by power consumption … anyway back in the real world.

  2. Rob / Aug 12 2009 4:48 pm

    Unfortunately, that’s how it’s gotta be. With the upcoming national release featuring multi-room viewing, it will need to constantly spin the hard drive in order to stream content to other networked DVRs.

    • Jim Fenton / Aug 12 2009 11:23 pm

      Even with multi-room viewing, there are things that can be done. First of all, not every customer is going to use that feature, and those that aren’t shouldn’t be penalized for its availability. Even for those that use the feature, there are ways of waking the DVR when another set wants to view its content. Why keep the receiver running all night (for example) when there’s nobody awake to watch the content?

  3. Doug / Aug 12 2009 7:57 pm

    Basically that power button probably switches an outlet on the back of the unit that you can plug another appliance into. Besides that there really is not much difference between off and on. When it’s off it’s can still be recording two shows at a time. Infact I imagine that the wattage is equivalent if a show is being recorded to the DVR, since while you are watching it is recording automatically.

    • Jim Fenton / Aug 12 2009 11:27 pm

      My DVR doesn’t have an outlet on the back, but I suppose that some might.

      I don’t have a problem with the DVR consuming power at the “on” rate when it is actually recording a program or two. It’s the power consumption when it’s truly idle that concerns me.

  4. steveko / Aug 12 2009 8:38 pm

    >That works out to a savings of 324 megawatts, just for DirecTV customers.

    In other words, about a whole average sized coal power station. Heh.

  5. Ellen / Aug 17 2009 12:11 pm

    I’ve read wayyyy too many articles in recent years about what they call power vampires (you can google “power vampire” and get lots of info), exactly because of the phenomena that you’ve noticed, and the huge amount of additional power generation that’s required to keep up with all this stuff. They also point to lazy consumers and power tranformers–the cell-phone charger, for example, that’s left plugged in even when the cell phone isn’t attached. Even if it’s a small amount, as you note, when multiplied millions of times, it really adds up.

    I bought a KillAWatt last year myself, and it has been fun (and interesting) to play with it. Wish I had something that simple that would help compare hard-wired items. For example: KWH to run a ceiling fan versus a high-powered plug-in fan. KWH to run the furnace rather than a couple of plug-in portable heaters.

    I have almost all of my computer equipment plugged into a master power strip that is turned completely off when I’m not using the computer, so nothing is in standby mode. I’ve done the same for all of my stereo/TV/etc. equipment; it’s all off almost all the time. This gets me into a quandary with my satellite box, which apparently periodically does some kind of download/update, so that every couple of months when I turn it on, I have problems with it being very confused. Oh, well, just more reason not to turn it on. 😉

    • Ellen / Aug 17 2009 12:16 pm

      P.S. Hard choices sometimes, though. For example, my walkie-talkies are left plugged into their charger all the time, even though I use them only a couple or 3 times a year, because otherwise they’re not charged when it occurs to me that I want to use them. I have a hand-held vacuum and a hand-held carpet cleaner that are plugged in all the time to recharge. But they’re so useful that I’m glad to pay for their power (in so many ways…). I wired in a timer-switch for my hot tub so that it doesn’t use electricity during peak usage hours–but the trade-off is that it resets daily to a lower temperature than I want. And I turn it off entirely over the winter. Which means no using it during those months at all, no matter how sore and stressed I am. 🙂

      • Jim Fenton / Aug 17 2009 1:42 pm

        I didn’t post all of the Kill-A-Watt readings I took on random devices around the house, but I was actually surprised at how little many devices take on standby. Disconnected cell phone chargers and the like seem to me to be “in the noise”. Very slight changes in behavior are enough to more than compensate. So, hang one load of clothes on the line this summer, and you have my permission to leave your unused chargers plugged in.

        The difference is that improving the design of satellite receivers and DVRs could save a lot without requiring a large scale change of behavior.

  6. MissingFrame / Nov 13 2009 1:59 pm

    A lot of the new wallwart adapters won’t even register current on my Kill-A-Watt meter. I just checked my phone charger with an ammeter and it takes 75 to 100mA. If you unplug your satellite receiver for 1 hour a day you’ll save as much as a dozen phone chargers left on for 24 hours 😦

    • Jim Fenton / Nov 13 2009 9:56 pm

      Unless you were charging your phone when you measured it, the phone charger should take a lot less than 75-100 mA; that’s 5-10 watts. But I agree that wallwart (plug-in) chargers at idle consume much less energy than things like satellite receivers (or, in my subsequent post, some mattress pads) at idle. I have seen public service announcements urging people to unplug their unused chargers, but there are far more productive things they could be doing.


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