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Submetering for Improved Building Operations & Maintenance Performance

Whether designed in or retrofitted, submeters are installed on the “building side” of the main utility meter to measure energy usage from the enterprise level all the way down to a single device or circuit.

Don Millstein

Don Millstein,

President and CEO

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Facility operators need ways to operate more efficiently, cost-effectively and with less downtime. When it comes to proactively managing energy consumption and demand, electric submeters and energy intelligence software are rapidly becoming the high-tech tools of choice, especially where facility operations and maintenance are concerned.

Quoting Department of Energy stats, Flex Your Power, California’s statewide energy efficiency partnership of utilities, businesses, government agencies and other entities, states that the commercial building sector uses approximately 66 percent of all electrical energy consumed in the United States. From 1989 to 2005, for example, consumption of electricity doubled, a trend that, if sustained, will likely see another 150 percent increase by 2030. Consuming roughly 23 million Megawatt-hours (MWh) of electricity, office buildings themselves account for almost 30 percent of all commercial energy demand. With energy representing some 30 percent of a building’s total operating costs [1], electrical consumption by end-use category may be extrapolated according to the break out shown in Figure 1.

Electrical Consumption

Figure 1. Commercial building electrical consumption by using source, based on data from a DOE 1999 end-use consumption survey. Notice that lighting and cooling alone account for 50% of all consumption, and the significant impact of plug load on facility demand.

Needless to say, the pervasive use of electronically powered technology across the facility landscape has placed unprecedented demand on the electrical grid. In many cases, however, the energy is wasted through inefficient equipment operation, avoidable demand peaks and other facility operational issues that are relatively easily and inexpensively mitigated through proper operations and maintenance procedures. In fact, it is estimated that a 30 percent reduction in energy use can lower operating costs by up to $25,000 per year for every 50,000 square feet of office space. Moreover, in terms of commercial asset value, this translates to every dollar applied toward increasing energy efficiency resulting in a three-to-one return [1].  

As shown in Figure 1, lighting and the HVAC/R load represent 64 percent of the facility’s energy consumption and a great opportunity for energy-efficiency monitoring. Typical electrical and electronic devices suitable for operations and maintenance programs include:

•    Boilers and steam traps;
•    Chillers and cooling towers;
•    Energy management and building automation systems;
•    Air compressors and air handling systems;
•    Fans, pumps and motors;
•    Lighting systems.

Typical Maintenance Strategies

There is much more to a proper and effective facility O&M strategy than simply repairing equipment after it breaks. Several different types of maintenance strategies may be employed concurrently by the facility to optimize system operation, reduce downtime and minimize disrepair. Since every facility is unique to its own operational needs, the following strategies may be combined in some measure to maximize system life-cycle effectiveness and cost-effective operation. Note that the Dept of Energy expresses relative costs in terms of dollars per horsepower per year [2]:

Reliable ControlsReactive—“run it until it breaks” offers the advantages of less staff required and a low cost of on-going maintenance, but can result in unplanned equipment downtime, increased cost for equipment repair or replacement, possible downstream equipment/process damage and others. At $18/horsepower/year, reactive is the most expensive strategy according to DOE (FEMP) statistics.

Preventive—equipment failure is avoided by regularly scheduled maintenance which provides the advantages of greater cost-effectiveness, flexibility, increased equipment lifespan and lower failure rates. Disadvantages include the continued potential for catastrophic failure, labor intensity, waste due to unneeded maintenance and others. At 12-18% cost savings versus reactive, preventive strategies typically cost around $13/horsepower/year.

Predictive—condition-based strategy that examines the current status of the equipment before determining what, if any, maintenance is required. Advantages include a 10x return on investment, 25-30% lower maintenance costs, 70-75% fewer breakdowns, 35-45% lower downtime and 20-25% higher productivity, according to DOE figures. The downside includes higher investment in diagnostic equipment and staff training, and harder to quantify savings potential. At $9/horsepower/year, predictive results in an 8-12% cost savings over preventive strategies and a 30-40% savings over reactive.

Reliability-centered (Table 1)—employs many of the same practices as predictive but takes into account that all equipment is not of equal value nor does it offer the same probability of failure. Less important equipment might be relegated to a reactive or preventive strategy. At a typical cost of $6/horsepower/year, the advantages and disadvantages of RCM are similar to predictive, but the former more closely matches facility resources to needs while decreasing costs even further.

Reliability-Centered Maintenance

Table 1. Reliability-centered maintenance (RCM) incorporates elements of other strategies, based on relative importance or value of the equipment in question. Meters are ideal, low-cost data acquisition tools for characterizing these loads. Source: FEMP “O&M Best Practices Guide,” P. 5.6.

Metering Approaches Useful in Facility O&M Programs

Whichever maintenance strategy combinations are employed by the facility, the usefulness and value of metering is beyond question, particularly in profiling the high-usage loads broken out in Figure 1. When properly used, that information can lead to dramatic economic savings of 20 percent or more by allowing facilities managers to: 

•    Chart energy usage;
•    Compare energy usage by day, week, month or year;
•    Monitor all utility services, including electricity, gas, water and steam;
•    Schedule energy data collections to occur automatically;
•    Evaluate, in real-time, the impact of critical load-shedding activities;
•    Determine specific processes that are not energy-efficient;
•    Identify poor equipment performers by benchmarking energy levels at multiple facilities.

Metering Strategies

Table 2. A number of effective metering strategies may be implemented by the O&M program to achieve a sliding scale of savings based on the hardware and software systems employed. Source: FEMP Fact Sheet, January 2005 [3].

Once meters are installed and commissioned, they may be employed in a variety of ways (Table 2), depending on the application, to control costs, diagnose equipment problems, allocate usage costs, set resource efficiency goals and any number of other uses.

Advanced Submeters

Figure 2. Advanced submeters like E-Mon’s Green Class series [4] provide a scrolling LCD display of CO2 emissions, kWh and other sophisticated energy measurements that can help users gain green facility certification points under the LEED rating system.

Essentials of Submeter Operation

Submeter manufacturers have responded to the “green challenge” by developing next-generation hardware and software tools that specifically address the measurement and verification (M&V) needs of LEED v3 and other green building energy initiatives dominating the sustainable facility market. Certified to ANSI C12.1 & C12.16 national accuracy standards, advanced submeters (Figure 2) typically offer a number of important functions for new construction or retrofit applications, including:

•    Scrolling LCD display of kilowatt-hour (kWh) usage;
•    kWh in dollars;
•    Current demand load (kW);
•    Cost per hour, based on current load;
•    Estimated CO2 emissions in pounds, based on DoE standards;
•    Estimated hourly CO2 emissions based on current load;
•    Net metering, including utility-delivered vs. user-received power and net usage;
•    Compatibility with BACnet, LonWorks, Modbus, Ethernet, RF and other popular building automation system communications;
•    Integration with automatic meter reading (AMR) systems for billing and analysis;
•    View energy usage and carbon footprint data via easy-to-understand dashboards accessible from standard web browsers;
•    Compatibility with water, gas, steam, BTU and other pulse-output utility meters. (Figure 3)


Figure 3. Whether designed in or retrofitted, submeters are installed on the “building side” of the main utility meter to measure energy usage from the enterprise level all the way down to a single device or circuit. Sold through distribution, today’s submeters are easily interfaced with water, gas and other pulse-output utility meters to provide a total facility energy snapshot.

Meter Dashboards Simplify Energy Data Presentment

Internet-enabled energy monitoring and data presentment dashboards [5] are gaining traction in the facility environment for displaying kWh, kW, peak demand, power factor and other energy measurements in real time, and historically, while also displaying the facility’s “carbon footprint.” This allows facility occupants to monitor their building’s carbon dioxide (CO2), sulfur dioxide (SO2) and nitrous oxide (NOx) emissions—while at the same time observing estimated energy conservation measures needed to compensate for the displayed levels. Figures 4-6 illustrate the sheer depth of energy information provided by a single electric submeter.

Demand Dashboard

Figure 4. Demand (kW) dashboard displays the metered values of main power panel “P” (blue) and an HVAC panel (red) in terms of coincidental demand for both meters. The compare button at the bottom of the screen displays another chart comparing the same set of meters for a different time range.  

Comparative Demand Dashboard

Figure 5. Comparative demand (kW) dashboard displays the metered values of an HVAC panel (blue) and two lighting panels (red, green).  When selected, the compare button at the bottom of the screen displays dual charts comparing the same set of meters at different time ranges.  

Carbon Footprint Dashboard

Figure 6. This carbon footprint dashboard displays the real-time and historical environmental impact of a specific meter based on consumption (kWh). The main power panel “P” in this example is characterized in terms of kWh today; number of trees and forest acres required to absorb the CO2 in one year; and an extrapolation of equivalent gallons of fuel consumed and miles driven. The CO2 dial at top displays the equivalent emissions for the day, with the maximum being the highest recorded level. 

The Bottom Line is Always the Bottom Line

The type of sophisticated energy data needed to manage today’s commercial and institutional facilities is beyond the capability of the master utility meter to provide. As first-level data gathering tools in the facility load-profiling process, submeters provide high-accuracy 15- or 30-minute snapshots of energy use (kWh) and demand (kW)—at the enterprise level all the way down to a specific circuit or item of equipment. Submeters are an easily installed, versatile and scalable solution for obtaining the degree of energy intelligence granularity needed to optimize today’s facility operations—no matter what type of facility is being monitored.

From an Operations and Maintenance perspective, meters help identify operational inefficiencies, including revealing trends that may indicate future problems. Demand spikes are also identified, allowing facilities professionals to reschedule high-energy drawing loads to off-peak times or stagger their duty cycles to lower the facility’s demand profile. Considering the many uses of metering in the O&M sphere, it doesn’t take too many “saved the day” scenarios for the metering technology to more than pay for its own installation costs. 

About the Author

Don Millstein is President and CEO of Langhorne, PA-based E-Mon. As a veteran energy industry speaker and author, Don is a former participant in utility deregulation in California, New Jersey, New York and Pennsylvania. He is a member of the FEMP task force, Alliance to Save Energy, the U.S. Green Building Council and other energy conservation-related organizations. He may be contacted at 800-334-3666 or

Sources and Links

[1] Flex Your Power “Best Practices Guide for Commercial Office Buildings.”
[2] FEMP “O&M Best Practices: A Guide to Achieving Operational Efficiency,” release 3.0 August 2010.
[3] Federal Energy Management Program Fact Sheet: “Facility Metering for Improved Operations, Maintenance, and Efficiency,” January 2005.
[4] Green Class advanced submeter with CO2 carbon footprint data: 
[5] Web-Mon Internet-enabled energy monitoring dashboard:

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