Sub-meters are meters installed behind a master meter. Master and sub-metering is common in tenant occupancies like office buildings, shopping centers, apartment complexes, and trailer parks. The master meter records all the usage to the facility while the sub-meters record only the usage of individual tenants or areas within the facility. This arrangement is desirable because each tenant’s usage is individually metered and can be separately billed.
Sub-meters may also be used when power suppliers charge a different rate for different end uses in a building. For example, if a power supplier offers a special rate for residential electric heating, some type of metering system is required to determine the usage for just the electric heating system. Installing a sub-meter on the circuits running to the electric heating system historically has been the cheapest and most direct way to get the usage information necessary to accurately bill the customer’s usage at the two separate rates.
The same need for sub-metering applies if a utility offers a special electric rate for electric vehicles. Again, the power supplier would need separate metering or sub-metering to accurately bill for energy provided to the vehicle and the residence since they have different rates. The smart meter of the future may have the ability to determine and track how much energy is supplied to a car versus a residence without the need for additional sub-metering at the location.
Sub-meters are also commonly used for load research. In this case the meters record usage patterns and characteristics of different pieces of equipment, and the data can then be used in forecasting models and other types of data requirements. They are also commonly used in large commercial and industrial applications so that energy managers can determine how each part of a facility’s operations is contributing to the overall energy bill. This can then be used to prioritize investments in energy efficiency.