RL78/I1B microcontrollers adapt various electricity meter metrologies for different regulations by country and realize the efficient power measurement by the combination of low active current 96uA/MHz, standby current 0.66uA (Halt mode with 32kHz oscillator and RTC backup on), 24-bit ΔΣA/D converter, phase adjustment circuits and high pass filter. CPU clock frequency can be minimized taking advantage of the efficient power measurement features, which includes the low power ΔΣ A/D converter 0.53mA/ch. RL78/I1B microcontrollers have +/- 1% high-accuracy high-speed on-chip oscillator with +/-0.05% frequency correction function and keep the system robust by the benefit of the accurate on-chip oscillator even when the external oscillator is stopped.