Web-based household power usage monitor

Energy & Sustainability Technology
Web-based household power usage monitor

Power usage monitors like the Kill-A-Watt are pretty cool, but what if you want to monitor usage for your whole house? What if you want to track usage in real time throughout the day, without stepping outside to read the power meter? What if you could do all this without messing with mains voltage. Kevin tipped us off to this Instructable by jasonT which shows you how to do exactly this.

This Instructable details a real-time web based household power usage monitor. The end result is a live chart in a web page that updates every 10 seconds with the instantaneous power usage for my entire house. The electrical current is measured on the main lines entering my home with AC clamps. The signal is then conditioned with a simple circuit and monitored by an ioBridge module. The ioBridge module takes care of feeding the data to the internet without the need for me to host a power hungry home web server. By using ioBridge widgets with a few JavaScript API calls on my web page, I am able to chart the data with Google Charts as it is measured and make kilowatt-hour calculations in real-time.

Instead of doing anything with the mains power, the author uses an AC clamp to sense power usage. It’s basically a transformer coil that you can easily place around the incoming power line, no wiring needed. It outputs a low voltage AC signal, which can then be converted to DC with a simple circuit so that it can be used as a measurement device for embedded systems like the ioBridge or an Arduino.

We’re all trying to cut our energy usage, but without decent measurement tools it’s hard to really tell when or where your major expenditures are originating. Hopefully, this sort of device will be a standard feature in most homes in the next 10 years, but until then you can make your own.

What tools are you using to measure your home power usage?

Real-time Web Based Household Power Usage Monitor

24 thoughts on “Web-based household power usage monitor

  1. Vrogy says:


    – and this balances the hypealicious twittering wallwart from t’other day out, and then some.

  2. some jackalope says:

    There is no link to the instructible mentioned.

  3. Phillip Torrone says:

    @Vrogy – that’s a little mean, why put down one project to compliment another? limor and i entered it in the green gadgets competition and shared it as we entered it, the full project is almost done and will be posted for anyone to make, a few companies asked if they can make something just like it and we said sure – it’s not our fault that others wrote about it and liked – that’s a good thing usually? more people making, remaking… there are about 5 projects now that people have posted after we shared ours…

  4. Jason Striegel says:

    Sorry for buggering up the link. Should be corrected now.

  5. SBW says:

    This project measures VA, not Watts. They are only equal if the power factor is 1. In my house, the power vampires–the devices which consume power when they’re not operating–have an average power factor of 0.5, which would result in an error of about 100% when everything is turned off.

    Note: according to its specs, the kill-a-watt meter is inaccurate for measuring current or power factor for things which use less than 60 W. But the power measurement is good down to 0.5 W.

  6. Anonymous says:

    my tool to measure my home energy usage is my electricity bill. btw, it’s a lousy tool.

    this is a good idea… i just started tracking my car’s mpg with a little app for my ipod touch (but use excel or similar… i have just been to lazy i guess). i was bummed out to see that i was only getting 17 mpg… i wonder what i would think using something like this.

    why do these comments fail to post so often on this blog?? happens all the time. a captcha problem i guess. talk about energy loss… insert a captcha refresh please.

  7. SBW says:

    Aw, heck. While reading a bedtime story to my youngest, I realized that despite at least 20 years of training attempts by my wife, I did it again: I forgot to lead with why this is a good idea, and why I like it, and went straight to how to make it better, in a way that sounded like criticism. (It is obvious the author likes it–he built it!–so why do I need to tell him what he already knows?…)

    This is a cool project. Displaying the data on a web page so it is accessible from anywhere in the house is a nice solution to the display problem. Current clamps to tap off the mains so you don’t have to touch them is a good approach. And it provides data, which is something that I’m quite fond of.

    My eldest measured all the power vampires in 12 houses using a clamp-on ammeter. She discovered some of them appeared to use more power than seemed reasonable for how warm they were, so we measured their power factor using an oscilloscope to measure the phase angle between voltage and current. She went back and remeasured a house using a true-rms power meter, and we were both surprised at how much of a difference it made.

    One easy way to upgrade this project to true-RMS power would be to use a 4-quadrant multiplier chip (AD633?) to drive an AD737 True RMS-to-DC converter chip. Feed the signal from the clamp-on to the multiplier, along with a 60 Hz voltage signal from an AC transformer. But those chips, while cheap, require fairly high operating voltages–maybe some others would be easier to power.

  8. Phillip Torrone says:

    @SBW “why do these comments fail to post so often on this blog?? happens all the time. a captcha problem i guess. talk about energy loss… insert a captcha refresh please.”

    we are trying to fix this, sorry about that.

  9. SBW says:

    @Phillip: Ah, that unsigned post between mine wasn’t me. But the captcha problem did bite me on my first attempt to post my second post, although I didn’t lose the post, for which I’m grateful.

  10. dennisj says:

    Or you can just buy this:


    This is a “Blue Line Innovations PowerCost Monitor, Model# BLI-24000”

    Bought one for my retired pop – he has nothing else to do all day and loves this device. He was finally convinced that he didn’t need to unplug his router, cable modem, VCR, etc. when they weren’t being used.

  11. Vrogy says:

    @pt: Sorry, no harm is intended. More projects and more making is great, but I think less hype, and more useful projects, in the long run, would get you more attention- as well as helping out the average guy wanting to lower his energy costs more than the twittering kill-a-watt.

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