Current Cost

I decided to make a belated entry to the Current Cost meter craze (in Hursley) when some were being sold off at half price before Christmas. (For those not in the know, the device measure electricity usage for the entire home with the important addition of a serial output port.) I started off with Dale Lane’s GUI app at which point I was disappointed to realise that the historical data held by the device was only averaged.

Fortunately, I had a Linksys NSLU2 (aka ‘slug’) sitting unused upstairs. A couple of hours later the slug was duly unslung and I had modified Andy Stanford-Clark’s Perl script to simply dump the wattage and temperature figures to a file every six seconds.

The following graph shows our electricity usage for a typical day when we’re both out at work:
Electricity usage

The low water mark when we were away over Christmas was about 15W which is probably the combined effect of the meter, slug and ADSL router. The square peaks every 30 minutes or so are, I believe, the fridge kicking in. The tall slim peaks up to around 2.3kW are the kettle. I reckon the cleaner probably came around 3pm so those square blocks are a vacuum cleaner. Christine had the grill on for dinner around five o’clock and then the solid block in the evening is the washing machine oscillating on and off.

I find the temperature graphs equally interesting:
Temperature graph

You can see the temperature dropping through the night and then the heating kicking in around seven. We have gas central heating but I think you can probably see the pump on the electricty graph. The temperature just reaches 17°C before the heating goes off again. The presence of the cleaner was obviously enough to give the temperature another boost mid-afternoon before the heating (and cooker) comes on again for the evening. You get a nice oscillation with the thermostat going on and off. I’ve no idea what the peak at bedtime is all about…

All very interesting but as yet I’m not sure how this knowledge is going to help us get our bills down!

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