As of yesterday, I’m now the proud new owner of a centameter – a handy little display that shows you how many kilowatts of power your household is using at any instant. Here’s a picture:
As you can see by the mouse sitting next to it, it’s a reasonably small, neat unit. And, a little less obviously – its wireless! This is a great feature! It means (as well as being able to mount it semi-permanently somewhere), you can also carry it around as you check out your house’s (and its appliances) energy characteristics.
The way it works is with a neat white sensor unit installed either at your switch box, or meter. A sensor clicks on to the outside of the wire, and the sensor unit transmits this data wirelessly. The transmission is powered by a few AA (or AAA, I can’t remember) batteries which apparently last a year. The display unit picks up these signals and displays it.
You can configure the display to update every 6 seconds or 1 minute, and it can show current kilowatt consumption, current amount of CO2 production due to your energy consumption, and cents/hour. Additionally, the unit shows you the current temperature and humidity.
All up, it cost me around $200 to have installed. This included an electrician to come out and do the install – this is required simply because a licensed electrician is required whenever you’re dealing with switch boxes and metres.
And, after a day of use, I love it! Its better than TV – in fact, energy wise its a lot better; I’ve discovered that turning my TV on uses an extra 150 – 200 watts! 
But in all seriousness, some of the discoveries you make can be quite eye-opening:
- When my house is pretty much “off”, it uses around 250 watts – thats TV’s, etc on standby, the usual collection of digital clocks and (most significantly) 3 PCS that are on 24×7. These PCs were all selected as being low power consumption models
- When I turn on my “actual” work PC, consumption jumps by another 150 watts or so. This PC is a standard PC – not a low power model and that shows!
- The biggest impact is my (electric) hot water heater – when its running, around 3.6 kilowatts are drawn! I was quite surprised to see this, and was able to confirm it by turning the hot water off at the mains, and seeing the drop immediately on my centameter. Obviously, the hot water unit doesn’t run that often. Thankfully.
- And from the biggest to the smallest. I have a power board full of those little black plugs. You know the ones – phone chargers, camera charges, laptop. Nothing’s being used – they just sit there waiting for me to plug something in. Now, I’d heard that these things waste power when not being used – turns out they were collectively going through 30 watts. Or $26 a year. They’re all unplugged now!
End of the day, I can’t rate this highly enough. If you are even the faintest shade of green, this thing is a must have. But even if environmental issues bore you to death, being able to see how much your house is costing you in electricity bills is fantastic.
Hi there, just a tip for you internet savy types, you can order a Centameter direct from the Centameter.co.nz website cheaper and easier than you can purchase one in Australia. Cheers Gary
Hi,
I just found out about this little gadget and I’m interested.
Is it possible to attach at just one appliace? eg attach at the fridge cable and monitor that and then shift it to the freezer – or does it have to be connected at the mains board?
thanks
max
Hi Max,
The centameter is a whole-of-house gadget. So, the transmitter / measuring unit wraps around the main “in” wire to the house, and the display unit therefore shows the power consumption of the entire house.
There are alternative devices available that act as pass-through plugs – you plug your device (fridge, etc) into the device, and the device into the wall, and they measure the power consumption of that one device.
Its horses for courses – if you’re interested in the detail of one device, the latter is option is the way to go. If you want to watch your overall consumption, then something like the centameter is perfect.
I’ve been able to use the centameter to measure individual devices coarsely, but its not perfect. A device with constant power drain, like a TV, you can turn off and on, and watch the difference. But:
– the centameter is only accurate to 10 watts (so phantom power loads are pretty much invisible), and
– if something else changes in your house (say, the electric hot water system comes on), whatever you’re measuring gets lost in the noise
Those issues aside, I’ve been able to make some useful discoveries about power consumption of various devices just by using the centameter in this way.
As an aside, you might want to check out my new site:
http://www.low-impact.net
This is dedicated to environmental related posts. And, (coincidentally!) I just added a story about the centameter – it covers a lot of the same ground as this post, but does add some new info about other similar devices.
Hope this helps!
dasman
Thanks for the interesting post! There seems to be growing momentum for these types of devices. Was the $200 you said for the cost of the device and the installation? How long did the set up and installation process take?
Thanks,
Colin.
Hi Colin
The $200 was for supply and installation. Installation is straightforward (a simple clip on the outside of the wire going into your meter box), but regulations require that it be done by an electrician.
So, 5 minutes to clip the transmitter in place, 5 minutes to configure the receiver unit, and 5 minutes to take the owner through it all.