Power meters are great tools to measure power usage of any appliance at home. It may help to hunt down energy hungry devices and lower the usage by replacing them with more efficient. Why build an energy meter? The obvious answer would be – flexibility. When you build one – you can add as many features as you like. So here is one of solutions using accessible parts like Attiny85 microcontroller and several other parts like op-amps.
Power meter measures voltage, current and so power. Also it tracks frequency and power factor and is able to operate up to 100A loads. There is optional an RF transmitter which transmits data to displays or loggers.