I’m thinking of buying a new computer for home and thought I’d actually check power consumption (for a change) after noticing that (1) my work PC never goes to sleep despite my settings (I think it’s because it has a web server running on it as a “service”), and (2) a rather nice Gateway (Acer) tower I was looking at had a 750W power supply… I mean, 750W is enough to run a fan heater on low, or the same heat output as ten people.
Here’s what I’ve learned so that you don’t have to bother.
|Computer||Idle (Watts)||Max (Watts)|
|Mac Pro (original) 4×2.66 (1)||171||250|
|Mac Pro (2008) 8×2.8 (1)||155||318|
|Mac Pro (2009) 8×2.3 (1)||146||309|
|Mac Mini (2009) 2×2.0, 9400M (1)||13||110|
|Mac Mini (Late 2006) 2×1.83, GMA950 (1)||23||110|
|24″ Intel iMac (2, 3)||80-100||135 (or 240?!)|
|PC Intel Core 2 Duo E6400, 8600 GTS (4)||87||163.5|
|PC AMD Athlon 64 X2 5000, 8600 GTS (4)||102||210|
|MacBook 2.4, 9400M (5, 7)||9W (8)||90W|
|MacBook Pro, 9400M+9600M (6, 7)||10W (8)||100W|
My Kill-a-watt showed up (I got mine from thinkgeek.com). So far my very rough results are that my Macbook Pro (late 2007) uses about 30-35W on “idle” (but with the screen full brightness) and the most I’ve gotten it up to is 68W, but I suspect it could get to around 90W if I could max out the GPU and the CPUs simultaneously.
It will be interesting to measure the power usage of some flat screens to see how well a Mac Mini compares to the iMac (and, at the same time, how well the iMac compares to modular options).
Incidentally, the Macbook Pro’s power brick consumes 1W when it’s not attached to the notebook, and around 24W when it’s charging the notebook but the notebook is asleep. The figures above were for a notebook whose battery needed recharging — it’s probable that power usage goes down if the battery is fully charged.
Notes and Sources
- Apple Computer’s tech support pages
- From this thread; varying peak power consumption figures probably reflect different GPUs/tasks and bad methodology
- Power consumption includes built-in 24″ monitor (varying idle power figures based on brightness)
- The Truth About PC Power Consumption on Tom’s Hardware
- MacBooks have a 45 Watt-hour battery and have a quoted maximum battery life of 5h when using wireless, so we can safely assume idle power consumption will be around 9W.
- MacBook Pros have a 50 Watt-hour battery and a quoted maximum battery life of 5h, so 10W.
- Guesstimate based on assumption that peak power consumption will be about 10x idle — which seems like it’s roughly right based on the Mac Mini’s peak power consumption.
- Edit: rereading this post I realize there’s a major boneheaded mistake in it. Since notebooks never draw power directly they will always draw (significantly) more power at the wall than they actually consume, and batteries of course take more power to charge than they later provide. I’ll update my figures and graph when my “Kill-a-watt” arrives.
I just changed the energy saver settings on the Mac Pro I’m using. Good grief!
The average cost of residential power in the US is 11.03 cents per kWh (Department of Energy statistics), so that means a Mac Pro on idle costs about $0.39 cents per day, or $141.07 per year, versus $0.04 and $12.56 for a Mac Mini (and probably a similar value for an iMac which puts its display to sleep). And note that the “typical” PC consumes over half the power of a Mac Pro while offering dramatically lower peak performance (as the Tom’s Hardware article might put it — if you were working on a video project that required 8h of manual work and then a bunch of rendering, the 8h would be slightly reduced on the Mac Pro vs. the PC (which would be running close to idle) and then the Mac Pro would finish rendering in one-quarter the time and go to sleep.
Oh, and by the way, if you buy a cheap PC and keep it for two years leaving it switched on most of the time, you’ll have paid an extra $200 for electricity compared to a Mac Mini. As I said at the outset, my work development PC is running a web server as a “service” and thus will never go to sleep.
If you want to save power (and money), get a Mac Mini or a notebook (assuming Windows notebooks are similarly frugal) — unless you need serious horsepower, in which case Mac Pros start to look good (as long as you put them to sleep when you’re not using them). If you bought a Mac Pro because you think Apple is “green”, but you only use it for fairly minor stuff and you don’t put it to sleep when you’re not using it (heck, even if you do) then you’ve made a grave error — your Mac Pro is using as much power on idle as a typical PC under heavy load. Mac Pros are great in terms of computational power per watt, but only if you’re actually using them.