That Old Desktop is Costing You

…. It may pay to replace it. Literally.  I turned one off and it’s saving me $228 per year.

Sometimes savings are right under your nose.  So I’m a bit of a computer “aficionado” as it were.  And over the years I’ve automated a bunch of stuff in my house: for instance iTunes can simultaneously stream music to three rooms and two TVs which makes for, well, a cool multi-room streaming music and movie system without the cost of custom.   The center of this universe for me was, until a while ago, a 2008 Mac Pro with two Intel Xeon processors (four 3.0ghz “cores”) and four internal drives. 

Back in the day, this “beast” was a kind of the Big SUV of Apple desktops.  Fast and flexible, it could support tons of RAM and 4 big internal disk drives.  It also had a power supply to match.  Once Apple switched to Intel processors, souped up Mac Pros could hold their own with most super-high end Windows gaming machines in both performance and electrical consumption.

But a funny thing happened over the seven years of it’s existence: the world of “basic” machines caught up in speed; doing this while using less and less power.

I began to realize this when I setup a low-end 2013 Mac Mini for my wife.  First I ran the Geekbench benchmarks and to my surprise, this low-end Mac Mini equaled my loaded 2008 Mac Pro in overall performance at less than 1/4 the price.  Nice.  Then I hooked it up to a UPS (Uninterruptible Power Supply: an APC “Back-UPS XS 1300” if you need to know) and noticed something astonishing: this particular UPS has a load readout revealing the wattage being consumed at any given time, with the Mac Mini plugged in, it hovered around 30 watts with an external drive running as well.

“Hmmm, so what is that beast in the basement consuming? And what’s that costing me?” 

This consumption chart comes from Apple (full article click here) and gives an idea how a similar machine performs:

power consumption

Now, compared to the machine above, my Mac Pro had 4 drives humming versus a single drive, 12 GB RAM vs 1GB, and slightly faster processors…. and with those add-ons my UPS told me it was consuming more like 185w at “idle”, often running at over 200w.

Now if you do the math, that 185 watts  translates into….

  • (185w x 24hrs) / 1000 = 4.44 kWh consumed per day
  • times 30 = 133.2 kWh per month
  • times 12 = 1,598.4 kWh per year
  • times 0.143 cost per kWh (Maine) = $228.57 per year

In other words, by turning off that machine I save $228 per year.

After nearly six years of use, including four as my primary home-office desktop and two as my basement iTunes server and backup destination, it was time to send the beast to the great E-Bay auctioneer in the sky.

Ah, but what did I do with my iTunes server requirements?  Well, easy, I  added an external thunderbolt drive to my wife’s Mini to hold the music. Cost? about $175.  But even if I’d bought a brand new Mac Mini for $599, the payback would have been less than 3 years.  And note, the Mac Mini at idle uses between 10 and 12 watts, click here (vs 185 for my loaded Mac Pro). 

Yes, without the luxury of an extra PC lying around already, I would have had to purchase something. So say I purchased a new Mac Mini of equal or greater speed to the old Mac Pro, what happens to my electric savings then?

  • Mac Mini uses 10 to 12w at idle depending on model, I’ll use 11w
  • (11w x 24hrs) / 1000 = 0.264 kWh consumed per day
  • times 30 = 7.92 kWh per month
  • times 12 = 95.04 kWh per year
  • times 0.143 cost per kWh (Maine) = $13.59 per year

So my net electric savings from shutting down the Mac Pro drops a bit if I add back new Mac Mini: e.g. it drops from $228 in savings down to $215.

Moral of the story: If you have an older big desktop (PC or Mac) and you think it’s not worth replacing… think again, you may fund a newer, faster, more energy efficient unit simply based on the electric cost savings alone.

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