An integrating flow calorimeter for measuring and indicating the cumulative heat exchanged between a load equipment and a heat-conveying liquid circulating therethrough.A flow measuring device continuously measures the quantity of liquid circulated through the load equipment, and closes a switch for a predetermined fixed interval of time each time a predetermined quantity of the liquid has been supplied to the load equipment. The switch connects a differential temperature measuring device to an electrical power source, which can be a battery mounted integral with the meter.The differential temperature measuring device includes temperature sensors which sense the temperatures of the liquid supplied to, and exhausted from the load equipment. During the time the differential temperature measuring device is energized, the difference between the supply and exhaust liquid temperatures is converted into a pulsed output signal, in which the frequency of the pulses is directly proportional to the sensed differential temperature of the liquid.The pulsed output signals are transmitted to a counting device, which counts the number of pulses therein, and operates an indicating register which indicates the total quantity of heat supplied to the load equipment.The meter can also include a regulating device for adjusting the fixed time interval during which the switch is closed, to thereby compensate for manufacturing error in the flow measuring device.Also, the temperature sensors can be p-n juncture semiconductor devices, which are easily installed in existing liquid lines.