We almost always think about the BAS as a tool that is a critical part of energy management, so these systems are typically focused on those systems that directly use energy — notably the HVAC and lighting systems. Almost all commercial buildings are also users of water, though; the cost of water and sewer services varies from area to area and can become a significant expense. Worse, in areas where there is a shortage of water, there is not only a big expense but an imperative to conserve.