Central heating
Submeters take many forms. 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 metering company visits the apartments about once a year and reads the liquid level and replaces the vials. Some apartment owners have replaced the vials with electronic submeters that transmit temperature readings via radio to a master unit in each apartment. The master unit in turn transmits collated readings to the utility company, thereby saving both labour costs and inconvenience to both tenant and landlord. The master unit displays a number representing the current total of "heating value".