Units of trade in the Balancing Mechanism. Used in the BSC to account for all energy that flows on or off the Total System, which is the Transmission System and the Distribution System combined. A BM Unit is the smallest grouping of equipment that can be independently metered for Settlement. Most BM Units consist of a generating unit or a collection of consumption meters, and the energy produced or consumed by the contents of a BM Unit is accredited to that Unit.