Check whether an energy meter is running fast or slow. Use a pulse test with a steady load, or compare the meter’s kWh reading with a reference meter. The calculator shows the error percentage, a pass or fail against your tolerance, and the corrected units.
Follow your utility or regulator test procedure and the accuracy class of the meter. A steady load and a long enough test time give a reliable result. This is a calculation helper, not a calibration certificate.
Formulas used
- Expected pulses = load in kW times time in hours times meter constant (pulses per kWh)
- Error % = (pulses counted minus expected pulses) divided by expected pulses, times 100
- Reading method: error % = (meter under test minus reference) divided by reference, times 100
- Corrected units = recorded units divided by (1 plus error %/100)
Example
A meter has a constant of 1000 pulses per kWh. A steady 1000 W load runs for 60 seconds, so 16.67 pulses are expected. If the meter gives 16 pulses, the error is about minus 4%, which means the meter is running slow.
Related: AI Prompts for Electrical Engineers includes meter calculators and checklists for field work.
Frequently asked questions
How do I know if a meter is fast or slow?
Compare it with a reference. If the meter records more than the reference it is fast. If it records less it is slow. This tool gives the percentage.
What does a positive or negative error mean?
A positive error means the meter over-records. A negative error means it under-records.
How long should a pulse test run?
Long enough to get at least 10 to 20 expected pulses. Short tests with few pulses can be misleading because of rounding.
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