Abstract: Methods and apparatae for metering energy consumption in a mass transfer heat delivery system using acoustic signals. A first type of method uses the phase difference between two simultaneously generated acoustic signals to determine the flow rate of liquid through a station of the heat delivery system. A first transducer and second transducers are used to transmit the first and second acoustic signals, respectively, through the liquid in response to an applied drive signal. The drive signal is removed from the first and second transducers such that the first and second transducers may be used to detect the arrival of the second and first acoustic signals, respectively. A phase detector measures the phase difference between the two acoustic signals as detected by the first and second transducers. A second type of method uses time lag analysis. A first transducer is used to transmit an acoustic signal through the liquid towards a second transducer in response to an applied drive signal.