Heat meter

A heat meter, thermal energy meter or energy meter is a device which measures thermal energy provided by a source or delivered to a sink, by measuring the flow rate of the heat transfer fluid and the change in its temperature (ΔT) between the outflow and return legs of the system. It is typically used in industrial plants for measuring boiler output and heat taken by process, and for district heating systems to measure the heat delivered to consumers.^[1]

A heat meter attached to a heat exchanger in a District heating substation in a residential neighborhood. Right in white-blue: the calculator; in the center in bronze: the ultrasonic flow meter

Heat meters are devices used to measure the amount of heat energy consumed in heating systems, typically in residential or commercial buildings. They track the flow of hot water or steam through a heating system and calculate the amount of thermal energy used based on the temperature difference between the inlet and outlet. This data allows for more accurate billing and energy management, ensuring that residents or businesses only pay for the actual energy consumed. The heat meter market was valued at USD 2.13 billion in 2024 and is projected to reach USD 3.61 billion by 2033, growing at a compound annual growth rate (CAGR) of 6.1% from 2025 to 2033. ^[2]

Their growing popularity can be attributed to several factors:

1. Energy Efficiency: With increasing emphasis on energy conservation, heat meters help in promoting efficient energy use by making users more aware of their consumption.
2. Cost Allocation: In multi-dwelling buildings, heat meters enable fair and accurate distribution of heating costs among residents or tenants, avoiding disputes over utility bills.
3. Sustainability Goals: Governments and organizations are pushing for greener, more sustainable practices. Heat meters support these goals by encouraging energy savings and lowering overall consumption.
4. Technological Advancements: Modern heat meters are often integrated with smart building systems, offering real-time data, remote monitoring, and better integration with energy management systems.
5. Regulatory Compliance: Many regions are introducing regulations that require the installation of heat meters to ensure transparency and equitable energy consumption tracking, especially in district heating systems.

In Europe heat meters have to comply with the measuring instruments directive MID Annex VI MI-004 if the meters are used for custody transfer.

Elements

A heat meter consists of

1. a fluid flow meter - typically a turbine-type flow meter, or alternatively an ultrasonic flow meter;
2. a means of measuring the temperature between the outflow and the inflow - usually a pair of thermocouples;
3. a means of integrating the two measurements over a period of time - typically half an hour - and accumulating the total heat transfer in a given period.

Heat Metering Technologies

Superstatic:

Principle:  The main part of the flow passes through a Venturi nozzle in the pipe,  creating the differential pressure to bypass the other part of the flow   through the fluid oscillator. pressure oscillations are converted into an   electric signal by a piezo sensor and detected by the integrator

Approval Rating  Class 2 MID

Billing Approved  Yes

RHI Approved  Yes

Power Supply  Battery / Mains

Mechanical:

Principle:  A traditional pulsed mechanical water meter supplied with   a separate integrator for energy calculation

Approval Rating  Class 3 MID (due to the Class 3 rating on the mechanical meter)

Billing Approved  Not for non domestic

RHI Approved  Not for non domestic

Power Supply  Battery / Mains

Ultrasonic:

Principle:  working on the Doppler frequency sensors installed in upstream and   down stream  picking up flow and disturbance along the pipe and   compensated by a temperature sensor.

Approval Rating  Class 2 MID

Billing Approved  Yes

RHI Approved  Yes

Power Supply  Battery / Mains

UK Heat Meter Regulations

•For any non domestic application where the meter will be used for Billing (including sub metering) the meter must be MID Class 2 approved - Class 3 is not suitable.

•Class 3 meters can be used for domestic billing

•Heat meters used for non domestic RHI (Renewable Heat Incentive) must also comply with accuracy class 2 or better of the Measuring instrument directive(MID)

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See also

• District heating
• Heat cost allocator
• Heating system
• Thermometer