The submetering of gas can take place in a broad array of techniques that once again depends on the system currently installed or is being installed (new construction) on the property. Typically, the largest consumption of natural gas is used for heating. The following describes the submetering solution for the three most common types of heating in multifamily homes.

Individual furnaces in each unit:

Units that have an individual furnace for heat generally have two options to submeter the gas usage. The first method is the use of a standard gas meter designed for this application and which directly measures the amount of gas. The meters are typically slightly larger than a football and are installed in-line with the gas line.

The second method is with the use of a “run time” device which is connected to the furnace controller. When the thermostat calls for heat, the run time device begins counting. If the furnace rating is known, in BTUs/hour for example, the amount of gas usage is calculated using a fairly straight forward calculation by multiplying the furnace rating by the time the furnace is on. In both cases, the metering device is connected to a wireless system for automatic meter reading.

Central boiler with baseboard heating:

Central boiler systems use one or more boilers to heat water that is distributed to each unit through a series of pipes. Each unit receives heat when the thermostat calls for heat and opens a “zone valve” that allows hot water to flow through in-unit baseboard registers. In this heating system style, the aforementioned run time device is connected to the zone valve controls and counts how much time each unit calls for heat. The total gas consumed by the hot water boiler, as typically measured by a house meter, is then allocated based on much heat each unit has called for over a period of time. Slight variations of run time devices are available to provide additional consistency in the measurement of heat usage.

Fan coil with central boilers or in-unit HVAC systems:

Fan coil systems will typically have a central boiler for heat or an in-unit heating and cooling system. Gas submetering in this case is typically done by connecting a run time device across the fan coil controller. Allocation is again done by taking the total gas used for heating and allocating amongst the units based on the run time of each unit. Some run time devices also use sensors to measure the difference in air temperature to do a more direct calculation of energy used. These devices generally are more expensive but can take out some of the variation for this type of submetering.