# Does it save energy?August 18, 2010 6:08 AM   Subscribe

My boss insists we turn off our dual 30 inch Apple monitors when we go to the bathroom. He says it wastes energy. But they're still plugged in to the wall and receiving power. How much energy is really being saved?
posted by captainscared to Computers & Internet (22 answers total)

The maximum power use of a 30 inch display is 250W when charging a MacBook Pro at the same time. The maximum wattage from charging an MBP is 85W, so let's assume that each monitor is using 165W when it's on. Energy Saver mode uses 1 watt, so each setup uses about 0.055 kWh for a 10 minute bathroom trip. The average retail price of a kilowatt-hour is 19 cents in New York, so each bathroom break costs your boss about a penny.
posted by mkb at 6:13 AM on August 18, 2010 [2 favorites]

In percentage terms, you're saving most of the electricity that would've been used to power the monitor while you were gone. Since you probably aren't gone long, it's still a very small savings in absolute terms. In cash terms, you might even be losing money over the long term because of the additional wear and tear on the monitor from being switched on and off.
posted by jon1270 at 6:14 AM on August 18, 2010 [1 favorite]

These monitors use about 150 watts (maximum) when on, and less than 3 watts when off, which is near enough to zero. So with two monitors, power consumption is reduced by 300 watts when they're off.

Let's say you end up switching them off for an extra 10 minutes a day during bathroom breaks. You are saving 0.3 kW x 1/6 of an hour = 0.05 kWh. If your boss is paying 10 cents a kilowatt-hour for electricity, that'll be 0.05 kWh x \$0.10/kWh = \$0.005. A whopping half a cent every day, per person that does this.
posted by FishBike at 6:14 AM on August 18, 2010 [3 favorites]

The 30" LED displays use ~165W when running and 1W in power-saving mode apparently.

Assuming you go to the bathroom for 15 minutes you've saved 2460W/minutes each time you go. If you go once a day every day for a year that's 639,600W/minutes or ~11 KWh a year. That's like 3% of it's energy per year assuming it uses 0 energy outside of business hours.
posted by public at 6:19 AM on August 18, 2010

When turned-off, the backlight is, obviously, not on, and that's the main power draw. That said, turning them off for the 5 or 10 minutes spent in the bathroom is silly. And, I suspect, the additional power-cycling throughout the day may shorten the life of the backlight.

Would your boss be open to enabling the screensaver whenever you leave your desk? You could assign a hot corner to activate it whenever you leave. That, or you could simply set the display to sleep after 1 minute of inactivity in the Energy Saver control. Or a combination of the two.
posted by Thorzdad at 6:20 AM on August 18, 2010 [1 favorite]

Wouldn't turning them off often mess with your color accuracy?

I would research this and mention it to your boss, as I assume with those monitors you are into some type of design
posted by moochoo at 6:25 AM on August 18, 2010 [1 favorite]

Doesn't it take more power to turn them off and on then to just keep on?
posted by xammerboy at 6:34 AM on August 18, 2010

How much energy is really being saved?

How much energy will be expended arguing with your boss and trying to convince him that you're right?

posted by nomadicink at 6:36 AM on August 18, 2010 [8 favorites]

Wasn't there research about the extra energy expended when a lightbulb is turned on and off. and how it it greater than the savings for the time it's off? Does this sort of principle apply to monitors too, i.e. does turning it back on use more energy than leaving it on?
posted by L'Estrange Fruit at 6:39 AM on August 18, 2010

Wasn't there research about the extra energy expended when a lightbulb is turned on and off. and how it it greater than the savings for the time it's off?

Mythbusters (I know, I know) covered this and tested a whole bunch of different lights, measuring the consumption turning the light on vs leaving it on. The basic result was for all lights (CFL, incandescent, LED) the energy break-even was well under a second, so you were better off turning the light off if you were going to be away longer than that. The one exception was long-tube fluorescent bulbs, I think the break-even was at 30 seconds. So from an energy standpoint you're almost always better turning the bulb off, even in the worst-case of the long tube fluorescent if you'll be away from the room longer than 30 seconds. Now I don't think they tested cold-cathode fluorescent lights, like the type of backlight I think the 30" display uses, but I suspect it's similarly true. So your boss is likely right in that it saves energy to turn off the displays.

But MB also tested wear-and-tear and created a setup that repeatedly cycled the lights on and off over a month, maybe on a ten second cycle or something like that. At the end of the month I think only the LED bulb was still working. That sort of intense cycling isn't apt to happen in a real-world scenario but power cycling does impact lifespan.
posted by 6550 at 6:52 AM on August 18, 2010 [3 favorites]

Sure he's not just trying to keep track of how long people are away from their desks?
posted by A Terrible Llama at 7:23 AM on August 18, 2010 [1 favorite]

Since the question is pretty much answered above, perhaps this is also helpful: No need to turn them off, just press shift-control-eject and your displays will go to sleep while the Mac stays on.
posted by jardinier at 7:26 AM on August 18, 2010 [21 favorites]

probably save more money in productivity if he brought in some fresh fruit every morning, adding fiber to the diet will cut that bathroom break down by 50-75%.
posted by any major dude at 8:06 AM on August 18, 2010 [3 favorites]

ArsTechnica just had a post on people focusing on the wrong things when trying to save energy.
posted by Good Brain at 8:27 AM on August 18, 2010 [1 favorite]

This is an unlikely scenario, but since most of the typical cases are covered above, I might as well put it out there... I don't know what line of work you're in. Maybe you're working on some sensitive projects that need to be kept secret. Maybe your boss doesn't want prying eyes seeing what's onscreen while you're away from your desk. Maybe there's a security risk at play that he didn't want to worry you with, so he said it was to save energy.

I dunno, seems like a long shot but you'd probably be able to gauge its likelihood better than I.
posted by The Winsome Parker Lewis at 8:29 AM on August 18, 2010

Maybe you're working on some sensitive projects that need to be kept secret. Maybe your boss doesn't want prying eyes seeing what's onscreen while you're away from your desk. Maybe there's a security risk at play that he didn't want to worry you with, so he said it was to save energy.

posted by L'Estrange Fruit at 8:38 AM on August 18, 2010

L'Estrange Fruit: "Where that's the case, there's usually a strong policy about password-protecting your screensaver and putting it on whenever you leave your desk."

In case anyone is curious, when the screen is woken from sleep, OS X will prompt for your login password IF the following is set (10.6):

In System Preferences, under Security, in the General tab, check the box that says "Require password _______ after sleep or screen saver begins" and from the drop down box, choose 'immediately.'
posted by jardinier at 10:05 AM on August 18, 2010

I think I probably agree that the power savings would be minimal, BUT there are two additional considerations:

Big monitors put out a *lot* of heat. If you're in a hot area of the world, this could be significant.

Also, the act of turning your monitor off and on once or twice per day is going to remind you that everything you do potentially uses and/or wasted energy, so it might increase awareness overall.

These are not the strongest arguments ever, but -- just in case they factor into his policy -- they are something to consider if you decide to try to convince your boss that your counter-arguments outweigh his arguments.
posted by amtho at 10:47 AM on August 18, 2010

I'd do whatever my boss said if it meant I got a 30" Apple Cinema Display on my desk.

Agree that it's a bit silly, but Control-Shift-Eject might become your new best friend for this situation. Puts the display to sleep, not the computer, so it doesn't take as long to wake up. Last time I had an Apple Cinema Display, its power button was (annoyingly) set to sleep/shut down the whole system.
posted by bhayes82 at 12:31 PM on August 18, 2010

It will take alot more energy, carbon resources and money to replace them when they die early due to heavyweight power cycling.

Aggressive sleep mode, sleep after 1-2 minutes, that will save plenty of money and the world at large.
posted by jkaczor at 5:22 PM on August 18, 2010

Don't forget to factor in the time you aren't working while waiting for the monitor to start up. That is costing the company a little bit as well. So if this isn't about waste of energy as waste of money spent on energy you may be able to use that in your argument.
posted by Green With You at 8:24 PM on August 18, 2010

2nding the "Pick your battles" comment. Know when to fight for things that matter. Know when to concede the things that don't.
posted by 2oh1 at 11:10 PM on August 19, 2010

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