PURPOSE: To obtain an electronic watt-hour meter from which errors can be easily measured and error-measured results can be easily recognized.

CONSTITUTION: A master meter 3 sends a reference electric power signal which is converted corresponding to a signal obtained from an electric power generating source 2 to the input section 9 of a meter 1 to be measured. In the meter 1, the signal corresponding to electric power is obtained by performing multiplication on the signal obtained from the source 2 by means of a multiplier 6 through a CT (current transformer) 4 and PT (transformer) 5 and a CPU 7 calculates an error by comparing the output signal of the input section 9 obtained through a counter 10 with the output signal of the multiplier 6 and displays the calculated results in a displaying section 8.