Energy meter apparatus

An energy meter apparatus for measuring energy use in a system having a fluid circulating there through, the apparatus comprising:

• a sensing unit comprising a first temperature sensor configured to measure temperature of the fluid at a first boundary of the system;
• a processing-reporting unit comprising a second temperature sensor configured to measure temperature of the fluid at a second boundary of the system;
• and
• one or both of a flow sensor and a pressure sensor, the flow sensor configured to measure an amount of the fluid through the system and included in one of the sensing unit and the processing-reporting unit, and the pressure sensor configured to measure a pressure of the fluid flowing through the system and included in one of the sensing units and the processing-reporting unit;
• wherein the processing-reporting unit is configured to establish and maintain a first communication channel for communication with the sensing unit;
• and
• wherein the sensing unit is configured to report sensor measurements to the processing-reporting unit via the first communication channel.