Energy Cost of Idling Electronics

Does anyone have an educated guess as to the amount of electricity consumed by electronic music equipment that is on, but not being used?

Specifically, I’m talking about a big Roland KC-500 keyboard amp, an 88 key controller keyboard, and sound module. I play it sometimes, but leave it all on 24/7; my roommate, also a musician, comes along and shuts it all off to “save power.”

I maintain that while the equipment isn’t actually being played, the power draw is miniscule - I’m guessing, less than that of a nightlight. Is there much energy savings to be gained by not leaving the stuff on all the time?

Here in New Zealand, we have a consumer TV programme that discussed this kind of thing just this week. The cost of leaving appliances on “stand by”, per appliance, ranges from NZ$4 to NZ$6 per year (the worst culprit, they said, was leaving the microwave on to tell the time. Said that uses more energy than the actual cooking).

'Cause we’re just Kiwis down here, I’d say your costs wouldn’t be that much different, even with the exchange rate. Your power rates could be murder!

Well…there are three things you can try:

  1. Write, or call the manufacturer. Many of them have specs on the power consumption when just on, and not in use.

  2. Use an ammeter to determine what the amp draw is.

  3. Well…ok, let’s WAG. To do this, let’s find out some things:

a) What is the power supply - is it an AC/DC transformer? If so, the maximum wattage and/or amperage is likely marked on the transformer (the big box inline with the power cable).

b) What power does the equipment use when played? This, of course, gives an upper bound.

c) If it has any lights, you can estimate draw for each light on.

In other words…hmm, I guess this is not a very helpful post then. Being the experimentalist I am, I would choose option (2) to find out.

Well, they may say that my Kiwi friend, but I simply cannot believe that at all. I would love to see if anyone could demonstrate this in any way. An LCD clock typically draws such a low amount of power it is difficult to see how it would amount to more than a few cents per year.

Um, both the microwave clock and the display are still running while the microwave’s cooking, so it’s a little hard to see how the power would be less :slight_smile:

BTW, the microwave at my work draws about 1780 watts when cooking, and 1 watt when idle …

A nightlight draws about 10 watts, which at my low rate of 5.5 cents/kWh works out to 0.055*(10/1000)24365 = $4.82/year (US).

My WAG is that your music devices are drawing 10 watts, except for the Roland KC-500 amp. Since it’s a 160 watt amp, I’d WAG that it draws 20-30 watts of quiescent power.

So, my guess is 50 watts max, maybe as low as 20 or 30. At my electric rates, this works out to somewhere between $10 and $25/year.

If you specify the model numbers of keyboard and sound module, I could probably make some better guesses :slight_smile:

Not to hijack the thread–but in the same vein, any one have figures on electric consumption with the typical computer set up we all have, monitor, box, speakers, printer, scanner when on but not in use? How about TV’s and VCR’s plugged in but not in use?

Energy 100

I think those figures are a bit exagerated, but the site is sprinkled with references to DOE and is signed
Lawrence Berkeley National Laboratory, so I guess one can’t just ignore them.

Well, maybe not ignore, but question rather. I’m a “World Expert” on coal power plants, and I make mistakes all the time. Always politely question authority if something really doesn’t seem right after you’ve thought about it.

However, in this case I would agree with their numbers in general. I have seen similar figures from our own energy audits - of about 2 to 3%. Perhaps they are accounting for appliances left on accidentally, or lights left on. Whereas our numbers were from “passive” use, including transformers.

At 150 Watts, the KC-500 almost certainly has a class B/AB output stage with two sets of power transistors handling the opposite sides of the output waveform. At rest, neither side is really working, so little to no current is being used. Even in use, this 150 Watt amp is rated to consume 125 Watts (150=125??? I know, but it does sound funny), which is as much power as two lightbulbs use. It’s not that big of a load.

The keyboard and sound module probably have CMOS circuitry. CMOS transistors tend to use less power, for what that’s worth. In any case, they’re not made to produce power so they probably don’t consume much.

If you want to get a rough idea of how much power the setup uses, shut the setup off and see whether the electric meter outside spins noticeably slower. I’ll bet that turning off a light will make a bigger difference.

For a really rough guess, you could check for any hot spots on the cases. If the setup isn’t dissipating any energy as heat or sound, then it isn’t drawing any either.

Yeah, look at the electric meter…

The reason for unplugging things is not only in electricity savings but to keep them from being zapped by power surges & to prolong life of an appliance.

HD manf suggest one turn off the computer at night if its not needed.

Thank you all for the responses! After reading them and the Energy 100 page, I’m now convinced it’s worth turning the stuff off. It adds up to pennies a year, no doubt, but that 5% figure surprises me enough to make me want to do something about it. Thanks!

During California’s energy crisis, I read an article that estimated the total US energy leakage consumes the output of 6 or 7 power plants.

Whether my cable box (Pioneer BA-6300) is on or off, it’s always the same temperature, rather warm. I’ve always wondered what in the cable box could need that much power when it’s off. It’s about as warm as my computer monitor case when it has warmed up (of course, the monitor draws much more power, and the case disperses the heat).

Someone around here clipped an article on this very subject, which mentions the studies done up at Berkeley, now expanded to office equipment. It appears to be from a publication ??? News (Science News?), vol. 159. They mention that their data is taken from the LBNL newsletter in an article by Jonathan G. Toomey & colleagues.

It refers to the earlier result of 50W in homes (and reports this as being in SN: 10/25/97, p. 266), and on office equipment:

The figures given for office equipment leakage :

computers & monitors : each 14.3 TWh
copiers : 7.6 TWh
laser printers : >6 TWh
Fax machines & inkjet printers : each 3 TWh

Note that this is consumption in some cases by devices which are simply plugged in, not just turned on and not operating.

For example, a computer monitor might use 5W at any time it’s plugged in. If you leave it plugged in all year, that’s about 40 kilowatt-hours a year. And if you live in California, that’ll be about an extra $200/year on your bill.

If you really want to shut down your power consumption, use a switched power strip for these devices. But please don’t use the power strip switch to turn them off and on (turn the devices off, then turn the strip off).

That seems a little steep to me, even for California. Here in Virginia, I pay $0.055/kHw, which would be $2/year for that 5W monitor. Is California really 100 times more expensive, at $5.50/kWh??? I’d have a $10,000 a month electric bill if I moved :slight_smile:


Here’s some power measurements from some items in my house:

line voltage: 123 volts, 60Hz, 1.2% THD

 off - 0.00A   0.0W   0.0VAR    0.0VA
 idle - 0.14A   8.7W   0.5VAR   17.2VA
 play - 0.20A  13.3W   1.6VAR   24.6VA

RCA DSS receiver:
  off - 0.36A  25.8W   4.8VAR   45.0VA
   on - 0.37A  26.2W   4.9VAR   45.5VA

JVC 31" TV:
  off - 0.00A   0.0W   0.0VAR    0.0VA
   on - 1.20A  77W    12.0VAR  140VA

Teac 100 CD player:
  off - 0.00A   0.0W   0.0VAR    0.0VA
 idle - 0.00A   0.4W   0.4VAR    0.6VA
 play - 0.11A  11.0W   0.6VAR   13.6VA

Sherwood 60W receiver:
  off - 0.00A   0.0W   0.0VAR    0.0VA
 idle - 0.37A  33W    13.3VAR   48VA

HP DeskJet 882C printer
  off - 0.00A   0.0W   0.0VAR    0.0VA
   on - 0.00A   0.0W   0.0VAR    0.0VA
printing - 0.22A   12.8W   4.1VAR   26.0VA

A = Amps, W = watts (real power), VAR = vars (reactive power), and VA = volt-amps (apparent power).

It looks like a mixed bag- either “off” really is almost no power at all, or it’s almost full power. For this stuff it’s easy to tell- anything drawing 20 watts is going to get plenty warm.


California power will cost you big time. I live in the desert and during the summer months, just about everyone here pays more for their electric bill than for their mortgage (for “average housing”). So we turn everything off, close the blinds and lay low for 3 months. When it’s really hot, we go to the movies for the “free” air conditioning.

(sorry, off track here - carry on)

I agree - I think there was just a slight math error in there…

Just an obvious note, perhaps. But I do hate it when I read articles (especially in USA Today) that will say things like “as much energy as X power plants”. Considering that a “power plant”, depending on how it is defined, can be anywhere from 100 kW to 4,000,000 kW, it is not a good measure of energy consumption at all.

Okay, the $200 figure was meant as a joke … actually, electricity prices are still regulated to consumers in California, so the prices are in line with the rest of the US (a few dollars a year for a 5W leakage appliance).

(news reports say the Federal government might order the power plant owners to refund money to the utilities out here … meanwhile the state’s busy signing contracts and trying to keep it secret. I believe rumors say they’re paying $65/MWh)

Im in California & the gov is paying $44M a day for elec, so our rates for elec are pretty low, 9.9kw. Natural gas, however is three times what it was in 2000. It dropped a little this month.

Anyway, the idea is not just about saving a few bucks a year but prolonging life of an appliances.