Monitoring method and system are provided for dynamically determining rack airflow rate and rack power consumption employing a heat exchanger disposed at an air outlet side of the electronics rack. The method includes: sensing air temperature at the air outlet side of the electronics rack, sensing coolant temperature at a coolant inlet and coolant temperature at a coolant outlet of the heat exchanger, and determining airflow rate through the electronics rack; and outputting the determined airflow rate through the electronics rack. The determining employs the sensed air temperature at the air outlet side of the rack and the sensed coolant temperatures at the coolant inlet and outlet of the heat exchanger. In one embodiment, the heat exchanger is an air-to-air heat exchanger, and in another embodiment, the heat exchanger is an air-to-liquid heat exchanger.