It might not look like it, but that is a wondrous thing. It represents the next step in home hacking with the current cost meter. It is a lead which connects the current cost meter to the serial port on a lower power PC that runs a simple Perl script that records our power usage. The PC runs a script that captures the information from the current cost meter (current power used, in Watts, and temperature in ‘C) and build pretty graphs that are then published on a local web server.

Here are some of the useful resources I used to get it done:

• This original post from jibble.org: making graphs using the current cost device.
• Crouching Badger’s experiences with the USB version of the cable with links to a simple perl script.

The Jibble post got me started, although not being a PERL programmer or RRD user meant some of the “easy to make” changes weren’t actually that “easy to make”. Having learnt RRD a bit more, I’m impressed with it – great for performance monitoring of all sorts of thigns. It will take something more to move me to PERL as a programming language – PHP is as non-visual as I’m going to get. Some other pointers that helped (and give you an idea what it is all about):

• Dale Lane has done a fair bit – it was good to meet him at HomeCamp (I like Dale’s daily electricity bill too – I’ve build something similar, but taking the Kilowatt hours figure from the Current Cost Meter).
• Likewise Nicholas O’Leary has a series of posts.
• There is also a Google code repository.
• Ben Smithurst’s posts were also very helpful – a full script that updates rrd and an sqlite database too.

A slight warning: the commonly used PERL script fails when the temperature goes bellow 10′C though (since the current cost prints a leading space then, which causes the perl string matching clause to barf) – keep your current cost warm or fix up the script .

I have been amazed at the power of measuring usage in changing behaviours. Measuring really is the first step to managing. Even more excitingly, I have noticed that my gas meter is readable (via a magnetic or optical sensor) so I should be able to track that too soon – as if I’m not driving the family crazy already. Here’s a day of our electricity use (with min, max and average power):

Current Cost Meter

Phase I is already underway, as we now have a current cost meter installed (get yours here thanks to Southern Electric’s discount). Setting it up took about 10 minutes. The unit has already paid for itself by identifying a few unsuspected power-hogging devices – our ambient power consumption has already gone down from 700 Watts to under 350 Watts. The kids want to get it under 200, and are now militant about turning every unused device off – in the case of my middle son that also includes power sockets with nothing in them, bless him.

Current Cost Sensor Unit

Our peak-burst power usage is around 3Kw for very short periods, so it may be feasible for us to go off-grid, at least from an electric perspective. The next step is to do a wind survey and see if that could supply our ambient power needs.

Later this month I’ll be heading along to homecamp, a UK gathering of home hackers, and will hopefully pick up some good ideas there…