Author Topic: iMac power requirements  (Read 4056 times)

SeaflyP

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iMac power requirements
« on: February 26, 2013, 03:42:20 PM »
As a new WeatherCat user I wondered about the cost of keeping my iMac awake 24/7 so that it could post data to my web site using Weather Cat. I did some measurements of power consumption which may be useful to others. First I wondered about using my laptop (MacBook Air 11" mid 2011; 1.6Ghz Core i5). Running WeatherCat only and with the screen off it uses 5W; with the screen on 10W. Remarkably little and a clear winner but... the reason for having a laptop is to take it away with me - D'oh!!! 

So what about my iMac? This is a full featured model which I configured for video processing (27" mid 2011, 3.4GHz Core i7,  SSD + 2Tb HD). When I bought it I was worried about power consumption since my previous iMac (27" late 2009) was less capable and had tended to get very hot!  However the newer iMac is noticeably cooler and my measurements of power use confirm its efficiency. With only WeatherCat running and the screen off it uses about 38W. Turning the screen on adds 10W to 100W going from minimum to maximum brightness. I was surprised to find that having a number of sleeping applications could easily add a further 40W i.e. double the minimum power consumption.  I haven't tried running WC under a different user to the sleeping applications, but doubt it would help. At present the iMac is logging the WC data to the SSD but I will need to change that at some point since space there is precious. Spinning up the HD will only add 10W to the power consumption.

So the conclusion is to run WeatherCat most economically, turn off the screen,  shut down all other applications, log to SSD (if you can), and use a relatively new computer!
Peter

Steve

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Re: iMac power requirements
« Reply #1 on: February 26, 2013, 06:50:36 PM »
Great info, Peter!

I've had my Macs running 24 hours a day since I started hosting mailing lists back in the late '90s. I've used Quadra towers, whatever the predecessor to the Mac Pro was, a couple of 24" iMacs (that cooked and died as Peter noted) and now the 27" iMac. I too have the screen turn off after an hour, but unlike Peter, I have a ton of stuff running all the time, plus I have 4 external Firewire drives running all the time. I don't want to know how much I've spent on Mac specific electric costs over the years.

But then I've been making auto insurance payments on anywhere from one to nine vehicles at a time for the past 43 years and never made a claim. I don't want to know how much that's cost, either, but I'm guessing I could have bought a small house with those premiums. With the Mac's electrical consumption, I probably could have bought an iPad.  [computer]

Steve
Steve - Avon, Ohio, USA


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elagache

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Portables and Minis for savings. (Re: iMac power requirements)
« Reply #2 on: February 26, 2013, 07:19:34 PM »
Howdy Peter, Steve, and WeatherCat fans,

Thanks for making the power measurements Peter.  I never thought of using the household watt meter on the computers to actually see how various states of operation effected the power consumption.

Your points about computer models are worth considering especially as the cost of electricity continues to rise.  Many WeatherCat users have switched to Mac Minis because they combine low cost and low power consumption.  However, a MacBook is also an option, especially if you can get your hands on an older one that still is powerful enough to run WeatherCat. 

Cheers, Edouard  [cheers1]

P.S. I'm with you Steve though.  At some point you've gotta stop pinching pennies and get on with your life!  The sad truth is though is that special interests are working very hard to raise our electricity bills in pursuit of a dubious ideology.  Perhaps the luxury of 24/7 computers will become hard to swallow eventually.

jace

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Re: Funny thing happened when changing Macs (iMac power requirements).
« Reply #3 on: February 27, 2013, 09:43:21 AM »
I bought a second hand mac Mini to use instead of my Mac Book, as I wanted to be able to use my laptop again ! I cannot vouch for power savings, but when I am not using the Mini I shut down the old PC monitor screen and let Weather Cat purr along in the dark 24/7.

Strange thing is, previously my Davis console and Mac Book were in my conservatory, probably about 40 or so feet from my ISS, and every day for 6 weeks I got a total comms failure which required W/Cat to be totally shut down and the Mac Book re-booted before it would work. This happened between 09:15 and 09:25 every day.

Got the Mini, it's in the lounge, 2 feet away from my mobile phone, about the same distance from my wireless router, I'm probably about 120 feet away from the ISS. Using the same cable from the console to the mini, and using Bluetooth keyboard and trackpad for the Mini,  and a old Windoze PC monitor. So I'm breaking all the rules regarding electrical interference for the USB connection to the Console and so far in 45 days have not had a comms failure.  [lol2]

JC

 

WCDev

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Re: iMac power requirements
« Reply #4 on: March 03, 2013, 11:24:54 PM »
Interesting info, thanks Peter!