Power use

I’ve had a Current Cost EnviR domestic electricity meter for a couple of years; it was given to me be the electricity company as part of an effort to reduce energy usage. Several people have connected these meters to Linux computers; I have connected mine to a Raspberry Pi.

The hardware is two parts: a sensor clamps around the live wire going into the main distribution board, and a small mains-powered display wirelessly receives readings. Mine has a serial port, and came with a USB-to-serial cable adapter. Connecting over serial (e.g. with screen or minicom), the device writes out a line of XML every 6 seconds, like this:

<msg><src>CC128-v1.29</src><dsb>00776</dsb><time>20:18:30</time><tmpr>25.0</tmpr><sensor>0</sensor><id>00077</id><type>1</type><ch1><watts>00496</watts></ch1></msg>

Various people have already written some code to read from the device and put the output in some kind of database. I found some code on Github and modified it to write to an RRDtool round robin database. My code on GitHub.

Example graphs

Last five minutes

Power usage graph for the last 5 minutes

Last fifteen minutes

Power usage graph for the last 15 minutes

Last hour

Power usage graph for the last hour

Last day

Power usage graph for the last day

Longer-period graphs have been excluded from this example.

Room temperature

The temperature sensor on the power meter seems unreliable.

Last week

Temperature graph for the last week