The ArduINA226 power monitor

ArduPicLab published the details on how to build a current, voltage and power datalogger with Arduino and the INA226 module:

In the past I have developed various projects of ammeters based on Hall effect current sensors such as the ACS712, or on High-Side Current-Sense Amplifiers such as the MAX4080SASA or made with operational amplifiers. All these systems have an analog output which must then be digitized. The INA226 sensor has a digital output and incorporates a 16-bit ADC for which a high accuracy and precision is obtained.

from Dangerous Prototypes