Kill-A-Watt meter - A worthwhile investment

SolarJohnSolarJohn Solar Expert Posts: 202 ✭✭✭✭✭
Everyone interested in energy use and conservation (and you are, because you're reading entries in this topic), should get a Kill-A-Watt meter.  I've checked nearly every plug-in device in my home with mine, and I'm putting together some interesting statistics.  As an example; I can see the cost savings that result from turning down my thermostat and using an electric blanket instead.  Soon I'll calculate the cost of cooking a meal with a slow cooker instead of using the stove.  Not only does my meter help me save money, I'm learning to conserve energy in order to get the most from my solar photovoltaic system. 

Another useful gadget I bought recently is a USB voltage data logger.  Since my small PV system doesn't have the ability to monitor itself, I use this device to monitor my battery voltage over time.  You can find more information about this product here:

For anyone interested, I write about my experiences on my blog:

Here's the affordable-solar link to the Kill-A-Watt meter:



  • System2System2 Posts: 6,290 admin
    Re: Kill-A-Watt meter - A worthwhile investment

    Just one important thing to keep in mind with the Kill A Watt meter.
    DO NOT use it on modified sine inverters. The power supply is of the capacitor/zeener diode type and the sharp corners of the modified sine wave will cause the capacitor to "pass" way too much current for the rest of the circut to handle, so will soon burn out. It will probably be OK for about a minute, if you want to do a quick check of some appliance, but any longer and you're asking for a puff of stinky smoke.
  • WindsunWindsun Solar Expert Posts: 1,164 ✭✭
    Re: Kill-A-Watt meter - A worthwhile investment

    The burnout issue with modified sine wave inverters has supposedly been fixed, according to the manufacturer. However, from what we see, it does not read actual power accurately, about 10-15% off. But that is common with almost any digital amp/volt meter when trying to read modified sine.
  • System2System2 Posts: 6,290 admin
    Re: Kill-A-Watt meter - A worthwhile investment

    Thanks for that info. Good to hear.
    Would love to know the serial number, after which the problem no longer exists.
    Perhaps someone will know?
    Mine is fine on pure sine, but the back soon starts to get rather warm on modified sine, so I can only guess how hot some of the internal components are getting to cause that.
  • whackamolewhackamole Registered Users Posts: 18
    Kill-A-Watt meter and modified sine wave

    This is from P3 International technical support response to my question regarding whether a Kill-a-watt has a problem with modified sine wave. My serial number is SG xxxxxx, and here is how they responded:

    "An early production run of the P4400 unit was not compatible with
    modified sine-wave inverters. Some generators employ these inverters.
    The incompatible units are identified with a lot number starting with
    "B." If you have a unit featuring a lot number starting with a character
    other then "B" your unit should work fine with the generator and

    Since your unit is a lot "G" unit and was manufactured much later, it is

    It is most likely that any newly purchased unit will not be from lot "B"
    as we have been shipping updated units for some time."
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Kill-A-Watt meter - A worthwhile investment

    thanks for that tidbit of info. that means mine is ok too.
  • System2System2 Posts: 6,290 admin
    Re: Kill-A-Watt meter - A worthwhile investment

    Very good info Wackamole, thanks for sharing!
    My serial # also starts with SG, so according to the info you received, it should be OK, even though it's arse gets pretty warm on MSW. Probably the internal parts are heavy enough to handle it. (runs cold on pure sine)
    Thanks for sharing
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