Electricity - How Much Does It Cost? II

This is a follow up to my original post about how much electricity costs us (in the UK) and how that applies to real world usage. Since I wrote the original post my electricity supplier announced increases of 15% to their prices, ouch. Using the previous calculated figure of 9.75 pence per KWh (1 unit) my electricity will now cost me on average 11.21 pence per KWh... double ouch. Has my income increased by 15%? hell no, will prices go up again and again? hell yes. What am I going to do about it? Use less energy of course (and switch suppliers again in May).

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So I bought myself a power meter with the intention of identifying how my power usage is distributed and where it can be cut. I bought, from amazon.co.uk, a Plug-In Power and Energy Monitor
This is a great little device which will give you lots of information about what your electronics are sucking up. The two main settings the layman will be interested in are how much power the device is using in watts and what that equates to in KWh (Kilowatt Hours is what your electricity supplier will quote you on your bill, see original post).

In theory if you were to plug a table lamp fitted with a 60watt bulb the meter would read 60 watts and also give you how many KW it would consume in 1 hour (0.06, see original post for calculation). I've tested it on a couple of 40watt lamps and the device is very accurate (allowing for inefficiency within the lamp and tolerance of the bulb).

Over the coming days and weeks I'm going to measure as many of my electronic devices around the house as I can. As a taster I've just done a couple of tests on my main workstation, the beast).

Firstly, with the plug in but the computer powered off it consumes 6watts (you'll notice that the network port LEDs will remain lit as long as the plug is in the wall). Even if I was to never switch the thing on again it would still sit there burning electricity. 6watts = 0.006KWh = .067p per hour = 1.61p per day or £5.89 a year. Remember this is not some theoretical calculation this is fact using up to date pricing. Just shy of 6 quid a year is not going to bankrupt me but I'd rather have £6 in my pocket than some huge company.

Next I powered the computer on and waited until it had fully booted and Windows had finished all it's housekeeping tasks (indicated by task manager the CPU was 99% idle). The power usage settled at 130 watts (not bad actually). Still, how often do you walk away from your computer leaving it on and idle only to return to it hours later? I know I'm guilty of that. So 130 watts = 0.13KWh = 1.46 pence per hour = 34.98p per day or £127.66 a year. Obviously you'll not leave a computer on for a year doing nothing but it's indicative of a small server sitting in the office doing nothing for most of the day. Also, I'd hope you had the Power Saving measures and profiles configured on the machine to power down the hard drives, go into sleep mode etc after a period of inactivity.

I then ran a Blender 3D render to fully load the CPU at 100% to see the effect on power demand. The watts used jumped to 195, again not bad for a 4 year old machine in my opinion with a very inefficient PIV 3Ghz CPU. I'll rip a DVD to see the effect of powering the drive and HDD along with 100%CPU usage in the future.

Look out for an ever increasing list of devices I've ran through my power meter in future posts. How much does that kettle cost to boil a cuppa? Anything with a little, red LED indicating standby will be of particular interest, stay tuned.

Update: The next post in this series can be found here.

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