PURPOSE: To enable reading a meter even at power disconnection by using an electronic display element that allows keeping of a display content as of before power disconnection, in case of power disconnection.

CONSTITUTION: A heated hot water quantity is measured with a thermal media flow meter 1, and an output signal is supplied to a microcomputer 2, then temperature sensors 3 and 4 detect the temperature of the hot water on the inlet and outlet sides, respectively, and respective output signals are supplied to the microcomputer 2. The micro computer 2, based upon these, calculates and integrates heat consumption per a unit time, and stores it in a storage device, then displays it on a digital display device 5. As a display element for the display device 5, an electronic display element, having the storing ability such as an electric chronic device, and ferroelectric liquid crystal, etc., which has memorizing ability by itself, are used. With this, even at power failure or electric disconnection, meter reading can be done by reading the display device 5.