Sustainable Facilities Tool General Services Administration

Submeters feed timescale measurements from control devices or sensors into Building Automation Systems, enabling enhanced management and performance monitoring of building components such as HVAC equipment, lighting, and renewable energy systems. The availability of submetering data provided at more discrete levels can be used by automation systems as part of fault detection and continuous commissioning, thereby identifying problems with installed equipment before occupants observe adverse effects in utility bills. Additionally, submetering data may identify abnormal energy and water consumption as a result of system faults that may not be recognizable in the entire building's utility usage data.

Integration with an Energy Management System: Integrating a submeter with a data acquisition system (DAS), either stand-alone or through an existing building automation system, is an integral part of a submetering program. As long as the vendor-supplied submeter software program uses ANSI standardized "open protocol" methods, the data generated by the submeter can be used in conjunction with any major brand building automation system program.

Submetering technology can drive long-term and deeper energy and water efficiency and conservation improvements by introducing a localized, continuous timescale of consumption data across systems and spaces. This refined timescale provides insight into daily, weekly, or seasonal O&M issues, occupant behaviors, performance of installed equipment (e.g., HVAC and lighting), and verification of installed efficiency technologies. A time-series approach to analysis also provides the necessary insight to drive energy and water conservation through changes in occupant behaviors or continual improvements to building O&M procedures as conditions change over time.

Renewable energy and on-site generation sources work hand in hand with system submetering to provide the monitoring and analysis of energy generation asset performance. Submeters for photovoltaic (PV) or solar inverters have proven invaluable in helping to optimize renewable energy performance as they enable more continuous and proactive management of onsite generation. Additionally, without continuous collection of submetering data, many renewable energy systems and their resulting generation are subject to lost production or loss of Renewable Energy Credits (REC) while awaiting traditional monthly O&M inspections. As a result, renewable energy systems are prime candidates for thorough and integrated submetering.

The commercial building management industry has established leading practices to implement an advanced submetering system for maximizing benefits. There are also established industry methods to develop lifecycle cost-benefit analysis that capture the resultant benefits and justify the implementation costs of submetering. Listed below are the common steps followed to successfully implement a submetering system:

• Develop an advanced submetering plan that establishes the intended objectives from a metering program as well as steps for risk mitigation if necessary. Examples of objectives can include enabling energy usage allocation throughout a multi-tenant facility or effectively managing energy loads to minimize usage based on a demand schedule.
• Identify energy data needs to ensure that required data is obtained to support the building system's intended use. The collection of specific data is necessary for analytical purposes such as trend analysis. The type of submeter equipment required and its placement should support program objectives and the data needs of building managers. Specific meters have functionalities that are based on the service provided and the type of meter. For example, advanced trending may require meters that provide frequent data collection (e.g. hourly or more frequent vice daily or monthly to leverage utility time-based rate programs).
• Develop and apply evaluation criteria that will identify how to reduce utility use in a cost-effective manner. For example, selecting buildings in a campus that can be cost-effectively metered requires the development and application of criteria that will consider lifecycle costs and quantification of anticipated benefits.
• Establish the implementation and installation methods of the submetering system. This includes specifying system financing, building and utility prioritization, functional requirements, data management system architecture, and a definitive timeline for installation and implementation completion. This step also includes a training plan for building management staff whose responsibilities include system and data maintenance.
• Conduct continuous performance evaluation to ensure the effective and reliable operation of the submetering system. This step includes quantifying the sustainment funding required to maintain staff, data management activities, and any additional training that may be required. Regular reviews are required to assess the effectiveness of submetering system functionalities and whether the stated objectives are being met. Additionally, further analysis can be conducted to determine whether submetering can be applied in other locations or utilities.