Prince William Water has identified a group of commercial water customers whose usage patterns vary significantly from the overall commercial customer class. This group of customers is comprised of large (at least 50 Equivalent Residential Units ERUs) industrial water users. The majority of these customers are using water for cooling and typically have a separate sewer meter.  

The volume of water used by industrial customers varies significantly from month to month and is usually seasonal.  The annual average daily usage per ERU for industrial customers is lower than residential and commercial customers; however, the maximum daily water demand is much higher than that of residential and commercial customers. This is important because Prince William Water purchases water capacity and designs its water system based on daily demand. 

Because this customer group has different usage patterns and impacts on the system, Prince William Water created an industrial customer class. Since Prince William Water purchases water capacity and designs its water system based on maximum daily demand, Prince William Water is also basing ERU calculations on maximum daily demand for industrial customers.