I have read quite a bit about Vampire energy over the last year, and it seemed like leaving your XBOX, laptop, etc, plugged in was a bad idea. Based on a few things I have read, it seemed that I was losing a few dollars a day from having my various adapters plugged into the wall, but not into my devices.
A couple months ago I decided to finally get a Kill-a-Watt and start some testing of my own. I've been gathering data and recording various notes in Excel and am almost ready to write up some detailed testing along with the costs of things, but I did notice a couple very interesting items.
With a couple of cell phone chargers disconnected from the phones, I plugged them into the Kill-a-Watt and found that they didn't draw any measureable power. Now the Kill-A-Watt might not be measuring this, but if it's < 1watt draw, that means not a lot of power being used. Even at 1 watt, across 24 hours that's 24 watt-hours, and a $0.10/kw, that's 1 penny every 4 days, or about $0.08/month. Not a lot of power.
I also tested my laptop charger, thinking that might be an issue. After all, I disconnect at times, but leave the adapter plugged in. Was there a significant amount of vampire power being used?
No. That also drew 0 watts according to my measurements.
The XBOX 360 was a different story, pulling a steady 2 watts after it was shut down. That's still a fairly insignificant amount of power, not enough to get me to unplug anything on a regular basis.
I've got more testing to do, and more measurements to make as well as some number crunching to evaluate power usage here at the ranch, but from what I've seen of a few IT related devices, they're pretty skimpy on vampire power.