Heat cost allocators are devices attached to individual radiators in buildings that measure the total heat output of the individual radiator.

For example, Central heating in apartment blocks in Belgium, Germany and Switzerland is sometimes submetered with liquid filled calibrated vials, known as heat cost allocators, attached to each of the heating radiators.

The Open Metering System OMS stands for a manufacturer and utilities independent standardization for Meter-Bus based communication between utility meters (electricity, gas, water, district heat, heat cost allocators) and systems in the field of Smart meter.

Heat cost allocators can be either electronic, where two electronic thermosensors and a microcontroller are used to calculate the heat consumption of radiator by the temperatures of radiator and air in room, or evaporative, where a special, calibrated liquid in a capillary tube records the total heat output of the radiator.