How to Calibrate Electric Watthour Meters

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An electric watthour meter measures the electricity that the devices of your home or business use in watts per hour. You can read the meter's output on its center display and reset it often to see how much electricity you are using over a specific period of time. Adjusting the meter is crucial if you want to get accurate readings from it. Calibrate the meter by turning its adjusting screws with a micrometer screwdriver.


Step 1

Locate the micrometer adjusting screws on the meter. The full load screw is typically in the right corner of the display plate and the light load screw is usually below the display on the right side.

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Step 2

Slow the meter's counting speed down by gently turning both screws in a clockwise direction with the micrometer screwdriver. Turn both screws counterclockwise to speed up the meter's counting speed.

Step 3

Check the meter periodically to see if the readings are calibrating to the speed you adjusted them to. If necessary, readjust the screws with the micrometer screwdriver to calibrate the readings to your desires.


Consult your watthour meter owner's manual if you aren't sure where the micrometer adjusting screws are located on the meter.

The light load screw typically speeds up or slows down the meter at higher rates than the full load screw. Adjust the light load screw if you want to make larger calibrations and adjust the full load screw if you want to make smaller calibrations.

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