Computer Power Use
Playing around with my P4460 Kill-A-Watt; picked up a couple of short cables that let me insert it into the AC circuit just before it goes into the computer (monitor, whatever), for much more convenient measuring:
Ancient iMac Core i3
My first test subject was a 2010 iMac 21.5" (Core i3, 12GB RAM, 500GB SSD, Ethernet networking, Bluetooth running for a wireless mouse). At first boot, waiting for login, it’s drawing about 80W. Immediately after login, when Activity Monitor shows 4 “CPU” units all spiked to 100%, it draws a maximum of about 120W. Not too shabby. Back to mostly idle (~2% System, ~4% User, ~94% Idle, with 1424 threads and 313 processes), it’s back to drawing about 80W (bouncing between about 78 and 82 watts). If I left it online 24/7 but mostly idle (which I used to do), it would consume 1 kWh over about 12.5 hours of operation. Over a 720 hour month, that would be about 58 kWh, which SCE charges from $.27–$.47 for, so, worst case, leaving it unused but powered on (assuming it’s not in “sleep” mode, which, well, it would be), that’s $27/month at the highest tier. In sleep mode it draws about 2 watts; after 50 minutes it had consumed 0.01 kWh, and predicted (at $.47/kWh) a monthly energy cost of about $5. To sit idle, in sleep mode. (And this iMac has an unnerving habit of spontaneously rebooting while sitting idle...) (I need to an instrumented test while actually using the thing. Whoops. Forgot.)
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| Kill-A-Watt Monitoring the FrankenMac |
Next up was my “balcony iMac,” a Late 2012 Mac mini Server (Core i7 2.3 GHz) with 16GB RAM and a 1TB SSD, connected to a Dell S2721D 2K display via DisplayPort, and using WiFi for networking and Bluetooth to talk to a Keychron K2 keyboard and Logitech M535 mouse. Turned off, it draws about 0.3W (monitor asleep, computer powered down). In general use (e.g., editing this post in Firefox), it’s using about 35W. I let it sleep for 15 minutes and the Kill-A-Watt showed 0.00 kWh used and, once settled down, about 1.9W power draw. At $.47/kWh, left asleep, this setup will cost about $0.03/day, $0.23/week, $1.01/month, and about $12.35/year. Reset the KAW and after another 15 minutes of being an actual computer, the KAW calculated $0.1/hr, $0.38/day, $2.68/week, $11.50/month, and $139/year. But that’s if the thing was being used constantly 24 hours a day 7 days a week. And even I’m not that overworked. This thing is about half the price of the iMac to run, and significantly faster and more capable (despite the computer itself being just two years newer).
Update: With Firefox and PhpStorm and BBEdit open and a YouTube video playing in a Picture-in-Picture pop-out, it’s averaging about 50W. Pausing the YouTube playback immediately shaved about 8W of consumption. When left idle for a few minutes and the screen shuts down, it draws about 14W (with the Mac Mini still running).
MacPro
Haven’t done this one yet. I’m scared to. (At least I can console myself with the fact that, in the winter, if I leave it running, I don’t have to run a heater.)
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