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Its a little niggling annoyance that always gets me in my office that when I work overtime and leave the office after everyone else I see row upon row of little orange lights where people have turned off their computers but left the monitor switched on.

I'm wondering; are there any estimates for how much power a monitor left in this condition uses?

I'm guessing it is not so much power. But surely more than if you actually turn it off? Or else why is there an off button...

If I can get some solid proof of it using energy then I can bravely and anonymously make a poster to remind people to save the planet by turning their screen off! ... or if I get proof that it makes no difference then I can have a load off my mind.

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Usually its around .5-10 Watts depending on the make/model/size etc. I would recommend getting a kill-a-watt meter and checking a variety of monitors to get a rough idea of the average. Then you could bring that up with regard to yearly savings. A 3 Watts average across 20 monitors per year is not nothing.

  • 6
    Due to the inaccuracy of the meters (typically .5%-1% of the peak power reading = 12W-24W for a 240V/10A meter) you'll get a much better result if you can access the common feed point for a number of monitors. In some offices this is easy as there are only a few wall mounted points and everything runs off extension cords. Others... you'd need to replug everything to get to there. – Móż Oct 3 '14 at 2:26
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Monitors typically have 3 power levels:

On -- you're looking at one. Standby -- screen is black, but the electronics are active. Sleep -- circuits are off except for a small one to monitor the line to the computer Off -- it turns into a fancy cookie tray.

I'm using a Dell U2412 21" monitor. I went to their web site and looked up the specs.

Max 72 watts, Typical 38 watts, Sleep/Standby Under .5 watts.

Look up your monitor model online to check. Your mileage may vary.

Given that the average North American household uses about 1000 kWh/month, if your monitor were in actual use all month (720 hours) at 40 watts it would use 28800 watt hours or 28 kWh. About $3 to $5 depending on your power rates. Most monitors are set to go to sleep after a few minutes of inattention. You are talking about cents per month.

In passing: Turning your computer off is a bad idea too.

My computer right now in active use (Mac Pro, 4 processor 6 drives, 3 monitors) is drawing under 200 watts. Half that is the monitors, half the computer. If it doesn't sleep at all when I'm away it uses 2.4 kWh/day -- about 40 cents at my power rates. That's $240 per year.

Ouch! you say. But the flip side is my computers don't break down. When I was sysadmin for a university math department, I averaged three disk failures per year -- out of 300 computers. With the standards of the time I should have had 15 failures per year. How much is your time worth?

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If the lights are orange, as you've said, then the monitors are in standby, and are using a minimal amount of power (power to light the amber LED, and power to wait for a wake signal).

  • Welcome to Sustainable Living! What do you consider to be minimal? Exactly how much power is consumed in stand-by mode? – THelper Oct 6 '14 at 7:20
  • That "minimal amount of power" is the typical 0.5 - 10 Wats mentioned in the Enigma's answer. – pabouk Oct 6 '14 at 8:58

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