How to Calculate the Power Efficiency of a Converter

Calculating the efficiency of a power converter is a simple matter of defining the input and output energies, in similar units, then determining the difference between them to get the percentage of power loss in the conversion. It is best to use a power meter to determine the voltage and current flow in and out to get your answer. Kill a Watt meters can offer these figures instantaneously, allowing you to accurately measure the losses of power through your converter.

Kill a Watt meter
Calculator

Instructions

- 1
  Plug the Kill a Watt meter into the input side of your circuit. If measuring a power converter in a home, you would plug it into the wall socket, with the power converter plugged into the socket on the Kill a Watt meter itself. Take a reading of the voltage as well as the current once a steady state has been attained.
- 2
  Multiply the voltage and the current to get a power consumption in watts. This will become Value 1, or input power.
- 3
  Plug the Kill a Watt meter into the converter. If measuring in a home, the converter should be plugged into the wall outlet, and the Kill a Watt meter should be plugged into the converter, with the load plugged into the socket on the front of the Kill a Watt meter. Take a reading of the voltage as well as the current once a steady state has been attained.
- 4
  Multiply the voltage and the current to get a power consumption in watts. This will become Value 2, or output power.
- 5
  Divide Value 2 by Value 1 and multiply by 100 to get a value, in percentage form, of the efficiency of your converter. For example, if your Value 2 was 95 and Value 1 was 100, 95/100 = 0.95 x 100 = 95 percent efficient.

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