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    MagicMirror² v2.20.0 is available! For more information about this release, check out this topic.

    Measuring power/energy cost on a 24/7 running pi

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    • M
      merek last edited by

      Hello newbie here,

      I got a raspberry pi 4 and an old tv monitor and I wanted to construct a magic mirror.
      Before I get started I’d like to know how much I’m gonna have to pay for leaving it on.
      I don’t know if I can turn off the tv screen with the pi, so there’s that.

      Is there any easy way that I can measure this, btw I have no clue when it comes to mAh or watts or energy bills, or whatever is needed.

      A clear video explanation is preferred instead of a textual guide 🙂

      S 1 Reply Last reply Reply Quote 0
      • S
        sdetweil @merek last edited by sdetweil

        @merek sorry, no video here

        power usage is measured in kilowatt hours
        1000 watts, used for an hour.

        watts is volts times amps.

        so look on the label for the power devices
        and get the volts and amps used. (not supplied)

        my pi4 power supply uses 120vac at 0.3 amps, so 36 watts per hour
        my 55 in tv uses 120v and 82 watts(already multiplied) (while turned on) (.5 watt turned off)
        so, that is 36+82 = 118 watts for both.

        multiply each and then add them together. (118)

        my power is measured and paid monthly,

        so multiply the value u have (watts used in an hour) times 24 * 30 for a months usage, mine 84960 watts/month

        divide by 1000 (kilo) 84 kilowatts/month * my power charge 8 cents/kilowatt is about $7 a month at 24hours a day usage. I blank the screen (tv doesn’t support programmatic turn off/on) so it should be less… haven’t measured it

        the TV usage from the manufacturer say $19/year, but they don’t expect 24/7 usage, and don’t provide the power cost info

        in spreadheet form
        631531bd-c2c4-4c46-92ba-104ea28550d0-image.png

        Sam

        Create a working config
        How to add modules

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        • thgmirror
          thgmirror last edited by

          @sdetweil you really pay only 8 Dollar-Cent per kw/h? We have to pay 25 up to 32 Euro-Cent in Germany:-( That are round about 29 up to 38 Dollar-Cent.

          @merek it will be less, I think, but it depends what the pi is doing. The power supply sdetwel described can deliver 36 watts, but it is not needed the whole day. Different Websites say between 12 and 20 Euro a year for the pi…the costs for screen will be much more.

          What you can do is to choose an other RPI-modell and/or deactivate functions you don’t need on the board (Ethernet, USB) …and buy a screen you can turn off by MM.

          S 1 Reply Last reply Reply Quote 0
          • S
            sdetweil @thgmirror last edited by sdetweil

            @thgmirror said in Measuring power/energy cost on a 24/7 running pi:

            @sdetweil you really pay only 8 Dollar-Cent per kw/h?

            yes, and I am unhappy as I had to renew my plan this year and it went up from 6.5c/kwh to 8c/kwh

            they have plug in power monitors you can then examine actual usage, like this

            Sam

            Create a working config
            How to add modules

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            • thgmirror
              thgmirror last edited by

              @merek Btw. it will not be possible to messure the amount with an ammeter. It is too low to be detected…OK, my ammeter is not able to do it…

              thgmirror 1 Reply Last reply Reply Quote 0
              • thgmirror
                thgmirror @thgmirror last edited by

                ah, just saw that Sam recommended an ammeter…this may work, mine (another one) not.

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                • T
                  thobach last edited by

                  If you are looking for some code to disable the monitor or if you want the use an infrared sensor to detect when someone is in front of the mirror and only then turn it on, you can check my module https://github.com/thobach/MMM-Gestures.

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