Power Switches that Aren’t
A 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.