A battery-powered consumption meter comprising: a measurement means for measuring a value relating to an accumulated volume of a fluid flowing in a connected fluid pipe system to make up a consumption meter representation of the accumulated volume, and a first communication means, which is a wireless two-way communication means arranged for transmitting the consumption meter representation from the consumption meter to an external device external to the consumption meter, and for receiving a communication (14a, 14b, 14c) therefrom, the consumption meter having at least two modes of operation comprising: a normal operation mode, and a calibration mode different from the normal operation mode; characterized in that in calibration mode the consumption meter is arranged to transmit the consumption meter representation to the external device in response to a request therefor from the external device; wherein the consumption meter comprises registration means for registration of the communication (14a, 14b, 14c) from the external device at the time of the communication (14a, 14b, 14c) from the external device; wherein the consumption meter has an internal clock, and wherein the registration means comprises means for registration of the time of the consumption meter at the time of the communication (14a, 14b, 14c) from the external device; and wherein the consumption meter comprises interpolation means for making up a consumption meter representation corresponding to the time of the communication (14a, 14b, 14c) from the external device from a set of values of the accumulated volume measured previously and subsequently, respectively, to the communication (14a, 14b, 14c) from the external device. a measurement means for measuring a value relating to an accumulated volume of a fluid flowing in a connected fluid pipe system to make up a consumption meter representation of the accumulated volume, and a first communication means, which is a wireless two-way communication means arranged for transmitting the consumption meter representation from the consumption meter to an external device external to the consumption meter, and for receiving a communication (14a, 14b, 14c) therefrom, a normal operation mode, and a calibration mode different from the normal operation mode; in calibration mode the consumption meter is arranged to transmit the consumption meter representation to the external device in response to a request therefor from the external device; wherein the consumption meter comprises registration means for registration of the communication (14a, 14b, 14c) from the external device at the time of the communication (14a, 14b, 14c) from the external device; wherein the consumption meter has an internal clock, and wherein the registration means comprises means for registration of the time of the consumption meter at the time of the communication (14a, 14b, 14c) from the external device; and wherein the consumption meter comprises interpolation means for making up a consumption meter representation corresponding to the time of the communication (14a, 14b, 14c) from the external device from a set of values of the accumulated volume measured previously and subsequently, respectively, to the communication (14a, 14b, 14c) from the external device.