These last few days, a little application has been running here which tracks energy (i.e. electricity) and gas consumption in the house, in a little window of its own:

That’s 640 watt and 1.333 m3/hr. These values are normally updated a few times a minute. There are still some wrinkles in the software, such as the gas consumption not adjusting properly when the meter stops fully, i.e. when no pulse is received once the central heating turns off.

The following systems are involved in this setup:

• some sensors and a transmitter based on an RBBB Arduino with an RFM12B
• a USB-powered receiver based on an Arduino Mini Pro with its own RFM12B
• a Linux server, i.e. a modified version of the Bubba/II NAS in this case
• the Mac notebook I usually work on, though it could be anything really

Only the first 3 items above need to be always on, with a combined power usage of less than 10W. Every 3 seconds, sensor readings are transferred and stored on the server, using a trivial text format for now. This proof-of-concept setup uses rsync to transfer the log from the server to the notebook every 20 secs, so the above window isn’t yet as real-time at it could be.

But even with such a crude setup it is easy to keep an eye on consumption – and by simply switching appliances on and off one can deduce their approximate power consumption.