Energy Measurement, So easy ETM™ Energy Meter The energy meter EX3 is specially designed for central air conditioning system to do cooling and heating measurement. It could measure and charge for cooling and heating. The energy consumed by the user is call calculated by measuring the temperature and flow rate of the chilled water (or hot water) flowing through the pipe. Install an energy meter EX3 on the user's inlet pipe and a temperature sensor on each of the inlet and outlet pipes, The energy is calculated by metering the amount of chilled water (or hot water) flowing through the pipe (i.e.; the flow rate and pipe size) and the temperature difference between the incoming and return water.