Power measurement

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As an IT (networking) guy, I have a lot of computer equipment that is using a lot of power. One of my friends once said to me if they had something like the energy measurement police and you where not allowed to use more than a specific amount of energy, they would probably arrest me. It made me wonder how much power I am actually using. To measure the amount of kWh that I am actually using per hour, day, weeks, months or even years I am using equipment of RFXCOM.


The equipment and software to measure my power is:

The picture below gives you an illustration of how this should work.

power-measurement-setup-small.png What basically the story behind the picture is is that:

Because my CT1021 energy meter is using an IR LED I needed to make a small adjustment to the Reflective-Optical sensor. (Open the 3,5 jack plug and cut the white wire (leave the copper and blue untouched!)


Usualy the  Reflective-Optical sensor is used for other kind of meters with a rolling counter with a small mirror on it. When the mirror shows up the Reflective-Optical sensor will count that as 1 pulse and 1 just like 1000 pulses on my CT1021 means that I used 1 kWh of power, it will probably mean a specific amount of water or gas is used.Some people have a energy meter with a normal blinking light. This people need a different sensor ... the Photo Sensor.


Well if everything is working as it should and Homeseer 2 is receiving the information and RFXCharts is installed and configured according to the guide you should see some charts.

My hourly power chart looks like this at the moment:


I hope you enjoyed my explanation on the energy measurment part of my overall domotica project ...

Energy Costs of my Energy provider

Measuring power or energy made me wonder how much energy actually cost, so I made some phonecalls and checked out my online account of the energy provider.

It seems that I have something called dubbeltarief which means I pay 2 amounts:

  • daluren 23:00 - 07:00 (weekends and nighthours and some public hollidays) = laagrarief
  • normal hours 08:00 - 23:00 (weekdays) = normaaltarief

The total costs comes to:

  • laagtarief = €0,2051 per kWh
  • normaaltarief=  €0,2482 per kWh

This amount is including the energy tax fee and the 19% VAT fee but exludes the Vastrecht fee and Transport fee.There are also other amounts I need to pay which comes in monthly or yearly:

  • Vastrecht = €1,99 incl 19% VAT p.m (€23,88 incl VAT p.y.) (The payment for invoice process and paymentprocess costs)
  • Transport fee = €182,46 incl. 19% VAT p.y. (The payment for a 3-phase connection to the energy provider (3 x 25A)
    total extra yearly costs are:€23,88 + €182,46 = € 206,34

In 2010 ( 7 March 2010 to be exact) I switched from my old energy provider (Eneco) to the the new one (E-ON) and my current energy price is: vasttarief €0,0833 per kW (vasttarief = 1 steady fee for all hours including evening and weekends)

Measurement per device

Currently my PC is using arround 222 Watt of power. This was measured with a different system PLUGWISE.

222 Watt = 0,222 kW (222 W / 1000)

0,222 kW = 5,328 kWh for 1 whole day (0,222 kW x 24 hours)

5,328 kWh x €0,0833 = €0,4438224 per day (24 hours)

€0,4438224 x 30 days = €13,31 per month to keep my PC up and running (day and night)

My 4 x 24" monitors (132 Watt) would've cost me €7,92 if they where on 24 hours a day ... but they are not because they go in sleeping mode when I am not sitting behind my PC.

Here is a screenshot of my current power usage (and the power usage from the beginning of the day) for the PC:

pc-powerusage.png Here is a screenshot of my current power usage (and the power usage from the beginning of the day) for the 4 x Monitors: