The ERU is a billing unit defined by ordinance as an impervious surface with a measurement of 2,788 sq. ft. Commercial parcels with the Utility’s service area (non-flat rate parcels) were individually measured using GIS/aerial photography to determine the extent of each parcel’s impervious area, which was converted to ERUs by dividing by 2,788 sq ft/ERU. As an example, a large apartment complex with retail that measures 27,880 sq. ft. of imperious area will be divided by 2,788 sq. ft./ERU for a total of 10 ERU’s. In turn, each ERU is billed at $3.75 for a total monthly cost of $37.50.