Saturday, July 03, 2010

Monitoring household power with a Clipsal Cent-a-meter

A conversation at the recent Pycon in Sydney got me thinking about reducing the base load power use at our house.

Today I purchased and installed a Clipsal "Cent-a-meter", $148 from AGL.

You install a sensor that clips around the active line to the house in the fuse box, wired to a transmitter. Indoors a receiver displays the Kilowatt reading. It can also calculate what you're paying in cents (hence the terrible pun in the name), but I haven't set that up yet.

We had an electrician here for something else so I got him to help put the sensor in but it's a simple job with no electrical connection required.

Without any changes to the number of computers, plugpacks, set top boxes and other devices, we are running at about 0.74KW.

low reading.jpg

Turning on the stove, oven and kettle quickly spikes us up 6.7KW:

high reading.jpg

The plan is to watch this thing for a few days to get the hang of what's normal and then try to unplug all those un-used things around the house to see how much it can be reduced. I'll update this post to report how we go.


We've un-plugged a few devices and encouraged computers to sleep and this morning base consumption was 340W.

There's still a long way to go.

Off-peak usage

Up early this morning, 6:30, and I see we're running at 5.7KW. This will be the electric hot water system which is connected to the off-peak meter and remote controlled. When I put the kettle on we went over 8KW which is the highest I've seen so far. I wish this thing had a data logger...


Anonymous said...

Hi Peter,
Sounds like a great idea.
Had a look at the link, but we have two phase AC supplied to distribute the load, so does that mean we need to buy two sensors to integrate the currents to get a power total?
Would appreciate your feedback.

Peter Marks said...

The Clipsal transmitter has three inputs and I understand there is a three phase version with extra current sensors.

Not sure what happens if you use two phase.

So far I'm impressed with the read out, it updates every few seconds and easily shows the impact of even a single light being turned on.

Gavin Maxwell said...

I bet you could hack it, and with an Arduino do some data-logging Peter!

Peter Marks said...

Hi Gavin,

actually what occurred to me was trying to receive the 2GHz signal, it's probably quite a simple serial protocol.

Unknown said...

I've been using the Fluksometer. It's web and Wifi based, and is an open hardware/open software project. Disclaimer - I also sell the Fluksometer in AU, however more to promote energy conservation than profit. Also on that post some links to reducing my household energy consumption.


David, VK5DGR

Gavin Maxwell said...

Hi Peter,

I picked up a Green Planet monitor the other day - works pretty well. You must have a lot of stuff turned on. Our base is around 2-300W - that's a few lights plus the Mac, AppleTV, routers etc. It was below 200 when I crawled into bed last night.

This unit uses a 433MHz signal, so I have a little receiver that plugs nicely into my Arduino gear. Need to figure out the baud-rate that's being used then punch the data out to Pachube.


Peter Marks said...


That's something to shoot for. I've been getting technical support requests such as "the dvd player's stopped working" which are a result of me running around unplugging things.

What's needed is some sort of in-line mains gadget that completely disconnects if power drops below, say 10W.

Let me know how you go decoding the RF, I'd love to put a logger on mine, one idea is to rig an arduino data logger direct to the current sensor that seems pretty simple.