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Fun with a Power and Energy Monitor

Continuing the to-be-short-lived theme of my Computing Adventures at Home I recently purchased a Plug-in Power & Energy Monitor from maplin.

Since then my wife has looked increasingly concerned at the frequency with which I seem to be turning devices on and off in the house to attach my new toy.

My main motivation for the purchase was to check the power consumption of the server I run at home. This is a machine that I bought about a year ago and thought it would become my new desktop and part time gaming machine. Foolish really, as I never have any time to do any gaming so it quickly retired to take up a role as a big phat virtual server. It runs a number of Virtual Machines pretty much 24-7 including my Windows Home Server (what an awesome product), my source control and a development web-server.

I was worried that, given the intended purpose of the machine, it was probably chewing through electricity like Augustus Gloop gets through Wonka bars. I was also curious to test the now, commonly held theory that most chargers consume the same power no matter whether the charging device is connected or not.


Here’s my new toy with my mobile phone charger plugged-in (sans phone).

Plug-in Power & Energy Monitor

The good news, as you can see, is that when the phone isn’t plugged in the charger draws so little power that it doesn’t register at all with the monitor. This compares well to the 4 Watts it draws when the phone is connected and charging.

I found this pattern held true for the vast majority of chargers around the house – including my primary Lenovo laptop charger which drew less than 1W when the laptop wasn’t connected which compares well to the 50W when charging the laptop's battery.

On that note though, the one rogue(ish) device I found was my secondary laptop charger which is a Kensington Power Adapter (K38047EU) which drew 4W even when the laptop wasn’t connected.

This is a shame as I use the Kensington as my ‘docking station’ (a bunch of wires on my desktop at home, not an actual docking station) and thus this charger is plugged in all the time and doesn’t travel with me. I should probably swap their roles.

My Server

So what about the server I had at home? Well, I was reasonably pleased to find that it was only drawing ~125 Watts (only!). This is still quite high but I genuinely thought the measurement would come in well above 200W so was quite happy about this.

However, the machine is full of bits that it no longer needs. For example, it’s entirely headless now and I always remote into the box over the network so there’s truly no need for the powerful graphics card it has. Or the Blu-ray drive. Or the normal DVD +/-RW drive.

So I set about removing all this unnecessary chuff to see what difference it would make to the power consumption and I’m delighted to report that it dropped down to a much more reasonable ~105W. I’m pretty happy with that for now.

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Josh Post By Josh Twist
5:11 AM
23 Jun 2009

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