Our e2 Classic Energy Monitor is simple to install and easy to use. A mini current sensor is clipped on to the supply cables. A lead from the sensor is plugged into the energy transmitter, which then wirelessly sends real time data to the energy monitor. The monitor receives the data and displays the demand in kilowatts of energy being consumed at any given time. The e2 OPT may be programmed for various rates, ensuring that the cost of your energy is accurate.