Some groups of customers are metered and billed in bulk (as one entity) by the utility (DisCo). These groups include private residential estates, shopping complexes, markets, student hostels, police/military barracks, etc. These groups therefore have to put in place their own internal billing mechanisms to ensure all end-consumers pay their fair share. The metering system used in this type of situation, which is managed by the group itself, is known as sub-metering