I have wanted to do this for a while now, to see what the first run results would be, so I toddled over to Think Geek and purchased a Kill A Watt. They have a couple other models, a Kill A Watt EZ and the Watt's Up Pro – but they are too rich for me, so I opted for the $25.00 option.
Watt meter in hand I unplugged my entire system which is connected to a battery backup, and plugged in my new toy. Here are the results:
Windows Vista Home Premium (SP 1)
- Spiked to 301 watts during boot (just after log in)
- ran at 279 – 291 watts sitting idle 3-5 minutes after boot
- ran at 182-191 watts while in pseudo sleep mode (monitors off and hard drives off)
- after 24 hours – 4.83 KWH
Windows XP Pro (SP 2)
- spiked to 302 watts during boot (just after the loading screen came up)
- ran at 255 – 265 watts sitting idle 3-5 minutes after boot
- ran at 155 – 165 watts while in pseudo sleep mode (monitors off and hard drives off)
- after 24 hours – 4.53 KWH
Conclusions
If I take these results and factor in the national average for electricity costs of 9.78 cents, then it costs me roughly $175.00 cents a year to run my machine under Vista, and $160.00 under Windows XP. I have both machines set to turn the monitors off after 15 minutes, and cycle the hard drives down after 3 hours of inactivity.
There are a couple of reasons why this surprised me, first being that I have more drives being used under XP with one of my drives not being recognized (since the raid drivers don't work) under Vista. The second being the much expanded power usage controls that Vista has. Being that Vista has the capability to actual control how much of the CPU you use, I would have figured the power draw would be less, but it seems initially that XP handles power better. The biggest difference between the two though is how willing I am to actually allow the computer to go into sleep mode. There is no way I am going to put my XP install in sleep mode, or hibernation – it simply won't come back.
This isn't the truest test either, during both tests I was using my computer normally, but I played no games and didn't have Photoshop open or any of those things, it was only to see what I get for running the whole shebang.
I'm not done yet though, so expect another run at this. I'm going to test my Vista install again only this time set it to sleep after 1 hour. I might also run another set of 24 hours tests where I play some games for a couple hours during the evening, as well as turn of the machine when I go to bed, and before I go to work – which should drop my annual operating costs down to $45.00 or so.