The Entertainment Center Urban Legend

Urban legend and some more reliable sources (1, 2) claim that entertainment centers -- in particular your cable box -- rob you as you sleep.  In other words, a cable box allegedly uses a significant amount of electricity even when it is not on.  In this post, I report my Kill-A-Watt measurements for our entertainment center and attempt to prove or disprove this urban legend.

Three scenarios were measured: (1) cable box on, TV off, (2) cable box on, TV on, and (3) both cable box and TV off.  The results were somewhat surprising.

Note that there are devices other than the cable box and TV on the circuit monitored by the Kill-A-Watt, which complicated the analysis. The total collection of equipment is:

(1) the Comcast cable box

(2) an LG 42" LED TV (rated at 205W)

(3) a SONY AV Receiver (rated at 200W!)

(4) a SAMSUMG Blu-ray player / Netflix box (rated at 17W)

(5) Yamaha speakers (rated at 42W)

(6) a Motorola cable modem (rated at 9W)

(7) a Linksys router (measured to consume 2.5W)

(8) a MyBookLive network drive (rated at 10W)

(9) a Centech antenna signal booster (rated at 2.4W)

(10) a Toshiba laptop charger (measured to consume less than 0.1W when not plugged into a laptop)

These devices are plugged into an APS uninteruptible power supply (UPS) that probably consumes a bit of power itself.

Given all these devices running off of one source, it seemed it would be difficult to conclusively paint the cable box as an energy hog.  It turns out that it was possible, however, to do just that.

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In scenario 1 (cable box on, TV off), the entire electricity usage was measured to be 0.3 kWh over 6 hours, or 50Wh per hour.  Given that the modem, router, network drive, antenna booster and laptop charger collectively account for 25W, the cable box, at most uses 25W.  This assumes that the speakers, TV, AV receiver and Blu-ray player use no power when off, which is a questionable assumption since three of the four devices have illuminated lights even when they are "off".  Let's give these devices 10W, leaving the cable box 15W.  

Under this assumption, the cable box would consume 15 Wh x 24 hours, or 360 Wh a.k.a. .36 kWh.  To put this in perspective, of the 40-50 kWh we consume every day in the summer, the cable box allegedly accounts for .36 of those 40-50 kWh, or .72%-.9% of our energy use.  Translating to $: at $0.20/kWh, over a 30 day month, this energy use corresponds to a cost of about $2 / month for no actual utility to us, the equivalent of ceremonially burning one twenty dollar bill and one five dollar bill every December 31.

OK, so you are probably wondering why I didn't monitor just the cable box power usage to begin with.  The reasons are: (a) I wanted to know what the entertainment center as a whole was consuming, (b) it was much simpler to locate the UPS power cord vs the cable box power cord that is all part of a tangled mess, (c) it didn't occur to me until I was writing the paragraphs above.  Anyhow, I'll now go measure the real-time consumption of the cable box both in on and off states.  Be right back...

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The direct real-time measurements of the cable box: 13W when on, and !!8.5W!! when off.  A good question is what the cable box is doing with those 8.5W while it is allegedly "off", but I digress.

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So even if we never watch cable for days on end, with the cable box **off**, we're still paying 8.5W x 24 hours x $0.20/kWh / 1000 (W to kW) = $0.04 every day.  Sounds like I'm a miser, but over 365 days, that comes out to about $15 per year.  That's with the cable box OFF.  And we don't fastidiously turn it off.

Here's probably the more egregious offense for leaving the cable box plugged in, even in an off state: the CO2 generated.  The US Energy Information Administration (EIA) reports that one kWh of electricity results in at least 1.2-2.0 lbs of CO2 dumped into the atmosphere.  In the off state, the cable box still uses 8.5W x 24 hrs x 365 days / 1000 = about 75 kWh, or about 100+ lbs of CO2 dumped needlessly into the air.  Now keep in mind that there are some 321 MILLION cable boxes in the US alone!  All dumping at least 100 lbs of CO2 into the atmosphere each year.  

Yet another perspective: burning 5 gallons of gasoline produces about 100 lbs of CO2.  A useful fact to be used in a future post.

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OK, let's move on to the scenarios with the TV on, and then with both the cable box and TV off.

Scenario 2, cable box and TV on: 1.34 kWh over six hours, or .22 kWh per hour.  The TV, rated at 205W, seems to use much less, considering that the 200W AV Receiver and the 42W Yamaha speakers are also contributing to the total power consumption.  To put things in perspective, the LED TV uses less than the equivalent of two 100W incandescent light bulbs.  I'd say that I'm impressed and surprised that it takes apparently far less than 200W to light up nearly one side of a 42" diagonal rectangular electronic device.  This goes to show how instrumental LED technology has been for reducing energy consumption.

Lastly, for scenario 3, cable box and TV both off: 0.4 over 8 hours, or 50 Wh per hour.  Similar to cable box on, TV off.  This squares with the finding that the cable box uses only 4.5W more when on than when it is off.  In other words, there should not be much difference in consumption between scenarios 1 and 3.

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The bottom line conclusion: The urban legend of the cable box energy hog is more or less confirmed. By unplugging the cable box, the TV, the AV receiver, the Yamaha speakers, the Blu-ray player and the antenna booster (leaving on only the modem, router, network drive, and laptop charger) when the entertainment center is not being used, we'll have cash to spare for a money-burning ceremony at the end of the year.  Better yet, we avoid needlessly putting 100+ lbs of CO2 into the atmosphere each year.