Usage of a utility in a multi-unit building is apportioned to a single unit by measuring the total usage of the utility using a meter unit to produce a total usage measurement, then positioning at least one sensor unit in a single unit of the multi-unit building and monitoring usage of the utility by the single unit using the at least one sensor unit to produce monitoring data. Then a processor unit receives the total usage measurement and the monitoring data and correlates them to generate correlated data. Finally, the processor unit apportions the total usage measurement to the single unit based on the correlated data.