Comments on: Kill A Watt

By: SKO

SKO — Mon, 14 Dec 2009 18:21:47 +0000

BTW… this post has ruined my life… I constantly think of how much wattage everything is using now

By: Simon

Simon — Tue, 10 Nov 2009 18:08:55 +0000

BTW, my MacBook Pro 17″ is using 34 watts when idle (100% brightness) and 65 watts with both CPUs fully loaded.

Interesting that I can tell when my build is finished by looking at the Kill-a-watt.

By: Simon

Simon — Tue, 10 Nov 2009 18:06:00 +0000

Huh, I’ve never seen a 240V washer outside of Europe before. Ours is 110V, but our dryer is 240V.

By: Eric Faller

Eric Faller — Tue, 10 Nov 2009 16:35:34 +0000

I just realized that last calculation assumed that you leave them both on 24/7, which will probably not be the case. If you turn them off at night, that’ll at least double the time.

By: Eric Faller

Eric Faller — Tue, 10 Nov 2009 16:34:10 +0000

Yes the difference surprised me as well. I think there are a couple of explanations of where the difference comes from:
- My laptop screen brightness was at about 75%
- The laptop has an LED-lit screen, which is more efficient
- My desktop monitor is much much larger than the small laptop screen
- The desktop has a lot more RAM (needing power)
- The desktop has CPU, GPU and PSU fans which are always on, but the laptop’s fans only come on every once in a while.

To answer your second question, if we assume a difference of 250 W between a laptop and desktop, then that’s a savings of 2190 kW per year, or $197. So it’d only take a few years to recoup the extra cost (assuming you were OK with the smaller screen of a laptop, etc)

By: Jason

Jason — Tue, 10 Nov 2009 14:20:01 +0000

Wow…Thats quite a difference. Assuming your laptop has a dual core processor, and you used your laptop screen at full brightness, your laptop uses 85% less energy (44W compared to 305W). Which raises an interesting question: how long would it take to recoup the extra cost of a laptop (over a desktop) given the significant energy savings.

By: Eric Faller

Eric Faller — Mon, 09 Nov 2009 16:48:24 +0000

Good questions. I just measured my laptop:
- Asleep: 2 W
- Idle: 25 W
- Heavy load: 44 W

Unfortunately there are a couple of problems with measuring large appliances:
- Big ones like washers use 240V plugs instead of 120V, and thus don’t work with the KillAWatt
- Some appliances like refrigerators turn themselves on and off at weird intervals, so it’s difficult to measure their average power consumption unless you leave the device plugged in for a day or more. When I’m done measuring all my small devices I’ll probably do that with the refrigerator.

By: Jason

Jason — Mon, 09 Nov 2009 15:40:14 +0000

Cool gizmo….I’d be interested in seeing what the difference in power consumption between a laptop (with battery removed) and a desktop computer is while attempting the same tasks. Tried connecting to any large appliances yet? – Your speakers cost $6.25/year, but what about your fridge, or washer…

By: Simon

Simon — Mon, 09 Nov 2009 09:02:39 +0000

I’ve had one of these for a while too and I’m still trying to find time to do an analysis of old devices vs new, i.e. computers, light bulbs, appliances, TVs, etc.