Monday, 26 March 2012

Power Meter Accuracy - Another Update

So I've left it just under a week since JSJS Designs got back to me to say they'd updated the WiFi Link and that should make it more accurate.

Here are the results.

Over the period my proper meter states I've used 75kWh.
Over the period my LightwaveRF states I've used 69.9kWh.

So the LightwaveRF readings are now under to the tune of 6.8%.  More accurate than the measurements I took before (it was 31% over).

I will continue to monitor...


  1. Nice blog - I'm at a similar stage.

    Have you managed to get one of the master/slave switch configurations working?

  2. Hi Pete
    Not as yet. I only bought a double light switch just to prove the concept. When I was researching this it looked like you couldn't have a pair of double light switches working in a master/slave configuration. It seemed that the master could be a double switch but the slave was a single switch.

    As the only master/slave configuration I have in my house are doubles I didn't look in to doing this.

    The guys from LightwaveRF might be able to help you. They were pretty helpful when I reported that the energy measurements were wrong.


  3. I just bought the WiFi Link and power monitor last week. I suspect it's not as accurate as the power monitor I had from British Gas. Reason being that the BG monitor update rate is much quicker - maybe 1 second?, whereas the Lightwaverf unit only sends a reading every 10 seconds. Things like fridge motors take a huge surge for a couple of seconds when starting up. This must happen dozens of times per day. If your update rate is only 10s then there's a good chance you'll miss a lot of the transient activity and fail to report it. Would be good to know whether the monitor sends the average for the last 10s period each time, or whether it's an instantaneous reading. Can you ask them?

    1. Hi,
      That's some great feedback, many thanks. I've never compared the LightwaveRF to another similar system so don't know how it compares. I can see how the 10s sampling period could mean transient spikes will be missed.

      Can I please ask that you contact LightwaveRF to ask about this? I don't have a hotline to them so it would be best if you asked (as you'll ask the question properly) and then you can handle any follow up questions.

      It looks like you can submit a ticket here:

      I'm interested in some of the longer term usage profile information you can get from the unit and as such take a sample every minute and store it. See some of my later blog posts for how I do this.


  4. Hi Paul,

    You seem like my sort of guy (dont panic - geek stuff). I've been automating most this year (with LightwaveRF) - but a long time in a professional capacity...

    Please take a look at my site? [guest:guest]

    If you want a play, send me an email.... :o)


  5. Hi Neil
    I love the UI you've put together for your home automation system. You're way ahead of me!

    How do you collect the temperature measurements from all the rooms?

    Cheers, Paul